CAD/CAM切削与热压铸瓷工艺在全瓷修复体中的应用分析

Background and aims Dental veneers have become increasingly required among patients, but little is known about the optical properties of veneers obtained from the same ceramic material through different processing techniques. Methods In this study we compared the translucency and the opalescence parameters of zirconia-reinforced lithium silicate (ZLS) veneers restorations fabricated through CAD/CAM milling and hot-pressing techniques on the upper central incisor. Eighty specimens divided into 8 groups (n=10) were sectioned (Celtra Duo) and heat pressed (Celtra Press) to obtain 0.8 mm thickness. The optical parameters were calculated from the color difference against different backgrounds. Analysis of variance, one way ANOVA and post-hoc multiple comparison tests were used to evaluate and compare the optical properties of the same material, with a significance level of p < 0.05. Results The processing method had significant effect on optical parameters. Celtra Duo HT proved to be the material with the highest transparency degree. The hot-pressing technique led to higher opacity than CAD/CAM milling technique. Conclusions For a bio-mimetic aesthetic prosthetic restoration, the ceramic materials must have the same translucency and opacity as the real tooth. The results of this study revealed that high translucency ZLS obtained through hot pressing technique was the material of choice, as it fulfilled these requirements.

The accuracy of newly developed ceramic materials is still being studied. Marginal and internal adaptation are known factors that have an essential impact on the long term success of dental restorations. The aim of this in vitro study was to evaluate the marginal and internal fit of heat-pressed and milled monolithic glass-ceramic restorations based on their ceramic type, processing technique, and in vitro thermocycling. Thirty-two crowns were studied and divided into four groups (n = 8), according to the ceramic material (feldspathic glass-ceramic (F) and zirconia reinforced lithium silicate glass-ceramic (ZLS)) and to their technological obtaining processes (milling (M) and heat-pressing (P)). A typodont preparation was scanned with a D2000 3D scanner to obtain identical 32 resin 3D-printed abutment teeth. Marginal and internal gaps were measured using the silicone replica technique under 40× magnification. The crowns were further cemented and thermally aged for 10,000 cycles After cementation and thermocycling of the samples, marginal and internal gaps were assessed using micro-CT (micro-computed tomography)) analysis. Data were statistically analyzed using statistical tests. Significant differences were found before and after cementation and thermocycling among the tested materials (p < 0.05). Related to technological processing, significant differences were seen in the marginal area between FP and FM (p < 0.05) Significant differences were also found in the axial and occlusal areas between the ZLSP and ZLSM. Thermocycling and cementation did not have a significant effect on the tested materials (p < 0.05). The technological processes influenced the marginal and internal fit of the crowns in favor of the CAD/CAM (computer aided design/computer aided manufacturing)technologies. Thermal aging had little effect on marginal adaptability; it increased the values for all the tested samples in a small way, but the values remained in their clinically acceptable range for all of the crowns.

OBJECTIVES this study aimed to evaluate the adaptation and fatigue behavior of lithium disilicate glass-ceramic (LD) monolithic crowns produced by press (combined with 3D-printing) and CAD/CAM milling (control) techniques. METHODS thirty abutment preparations with a chamfer finish line were produced with a dentin analogue material and scanned with extraoral scanner. Captured images were processed using CAD software to design a premolar. Blocks of LD were milled using CAD/CAM system. For the press technique, crowns were first 3D-printed using a polymeric material and the heat-pressing protocol was performed. Crowns were adhesively cemented to the abutments and scanned using micro-CT. FILES WERE PROCESSED AND CROSS-SECTIONAL IMAGES WERE ANALYSED IN FIVE MEASURING POINTS: marginal, axial angle, axial, occlusal angle and occlusal. Fatigue test was performed in a MTS universal testing machine (2 Hz, 37°C distilled water) using an anatomic composite piston, following the step-stress method. Failures were detected with an acoustic system and confirmed by transillumination. A cumulative damage-Weibull distribution (95% CI) was used to analyze the fatigue data. Gap thickness data were analyzed using Kruskal-Wallis and Student-Newman-Keuls tests (α=0.05). RESULTS CAD/CAM milling resulted in larger gap thickness in the occlusal area and smaller gap thickness in the axial angle and axial area than press (p<0.05). The probability of failure was similar for crowns produced with CAD/CAM milling and press. The most frequent failure mode was radial crack. CONCLUSIONS LD crowns produced using the combination of 3D-printing/press technique showed similar fatigue behavior than CAD/CAM milled control group, and resulted in smaller gap thickness at the occlusal region. CLINICAL SIGNIFICANCE A more controlled process can be achieved by replacing conventional restoration waxing with 3D printing, which in combination with the press technique produces lithium disilicate glass-ceramic monolithic crowns with good adaptation and high fatigue survival.

STATEMENT OF PROBLEM Whether additively produced zirconia could overcome problems with conventional computer-aided design and computer-aided manufacture (CAD-CAM) such as milling inaccuracies and provide accurate occlusal veneers is unclear. PURPOSE The purpose of this in vitro study was to compare the marginal and internal fit of 3D-printed zirconia occlusal veneers with CAD-CAM-fabricated zirconia or heat-pressed lithium disilicate ceramic (LS2) restorations on molars. MATERIAL AND METHODS The occlusal enamel in 60 extracted human molars was removed, with the preparation extending into dentin. Occlusal veneers at a thickness of 0.5 mm were designed and manufactured according to their group allocation: 3DP, 3D-printed zirconia; CAM, milled zirconia; and HPR, heat-pressed LS2. The prepared teeth and restorations were scanned and superimposed, and the marginal and internal adaptation were measured 2- and 3-dimensionally; the production accuracy (trueness) was also measured. The comparisons of the group medians were performed with nonparametric methods and a pairwise group comparison (α=.05). RESULTS Three-dimensionally printed zirconia revealed median outcomes of 95 μm (margin), 252 μm (cusp), 305 μm (fossa), and 184 μm (3D internal adaptation). CAM showed median values of 65 μm (margin), 128 μm (cusp), 203 μm (fossa), and 120 μm (3D internal adaptation). The respective values for the group HPR were 118 μm (margin), 251 μm (cusp), 409 μm (fossa), and 180 μm (3D internal adaptation). Significant differences (P<.001) between CAM and 3DP (cusp, fossa, 3D internal adaptation) and between CAM and HPR (all regions) were found, with the former group showing higher accuracies. The trueness showed median discrepancies of 26 μm (3DP), 13 μm (CAM), and 29 μm (HPR) with significant differences (P<.001) for the comparisons 3DP-CAM and CAM-HPR. CONCLUSIONS Three-dimensionally printed zirconia occlusal veneers produced by means of lithography-based ceramic manufacturing exhibit a marginal adaptation (95 μm) and a production accuracy (26 μm) similar to those of conventional methods.

Abstract Objectives The objective of the present study was to evaluate the marginal fit of three most commonly used veneers in dentistry. Materials and Methods A maxillary central incisor was embedded in a self-cure acrylic resin block, with the crown and 2 mm of the root exposed to facilitate standardized tooth preparation. Following the preparation, 30 elastomeric impressions were made to produce master casts. These working dies were then randomly allocated to three experimental groups, each consisting of 15 samples. Group I comprised indirect composite veneers (ICV), fabricated using laboratory composite resin. Group II included pressable ceramic veneers (PCV), manufactured using heat-pressed lithium disilicate. Group III consisted of computer-aided designing (CAD)/computer-aided manufacturing (CAM) ceramic veneers, fabricated through digital milling of lithium disilicate blocks. All veneers were fabricated in accordance with the respective manufacturer's guidelines and were carefully repositioned on the prepared tooth to evaluate the marginal discrepancy using a stereomicroscope. Statistical Analysis Three pre-designated points—mesio-labial, mid-labial, and disto-labial and mesio-palatal, mid-palatal, and disto-palatal on the labial and palatal margins—were measured. The values were recorded and analyzed with one-way ANOVA and Tukey's post-hoc test using SPSS software. Results ICV showed more variation with mean discrepancy of 189.24 ± 25.17 µm at cervical margin and 79.01 ± 11.68 µm at palatal area. PCV showed less variation with mean discrepancy of 48.2 ± 8.35 µm and 40.58 ± 9.47 µm at cervical and palatal areas, respectively. CAD/CAM-fabricated ceramic veneers showed mean discrepancy of 94.24 ± 9.00 µm at cervical and 52.72 ± 16.33 µm at palatal areas. Conclusions Pressable ceramic veneers showed the best marginal fit at both cervical and palatal margins followed by CAD/CAM veneers. Indirect composite veneers showed poorest marginal fit. The marginal discrepancy values were within the clinically acceptable range for PCV and CAD/CAM ceramic veneers. Clinical Significance It is of paramount importance that the dentist should choose wisely the veneer material taking the marginal fit into account.

The aim of this ex vivo study is to assess with digital microscopy the thickness of luting space of metal free FPP made with technologies: selective laser sintering, milling and pressing. Twelve metal free FPP were designed after two technological protocols. The first group was made with pressed ceramic (IPS E.max Ceram). The veneering was made with feldspalthic ceramic IPS (E.max Ceram). The second group of samples was made with CAD/CAM subtractive technology. The metal free infrastructures were digitally designed for milling in zirconium oxide discs (IPS E.max ZirCAD). The prostheses adaptation was measured and checked with dedicated silicone. The evaluation of internal adaptation with optical microscope is more accurate. The silicone has a resilient characteristic and may influence the results. The measurement made with digital microscope are accurately higher.

This study aimed to evaluate the marginal and internal adaptation of CAD/CAM crowns milled using two different milling protocols (fine or extra-fine) within a 4-axis milling machine. The crowns were fabricated from lithium disilicate ceramic (IPS e.max CAD) and resin composite (Tetric CAD), assessing their fit in various regions. The crowns (N = 40, n = 10) were milled from lithium disilicate and resin composite using a CEREC Primemill unit. Four groups were formed based on the material and milling protocol: EFLD (extra-fine lithium disilicate), FLD (fine lithium disilicate), EFRC (extra-fine resin composite), and FRC (fine resin composite). The crowns were measured using the replica technique, evaluating internal and marginal adaptation in 18 measuring points per specimen. Data were statistically analyzed using ANOVA and Tukey’s test. Resin composite crowns demonstrated a significantly better internal fit compared to lithium disilicate (p < 0.001). Marginal and internal measurements for resin composites were consistently smaller across regions compared to lithium disilicate. No significant differences were found between milling protocols except for the axial wall region (p = 0.001), where extra-fine milling resulted in smaller values. Resin composite crowns exhibited superior internal fit compared to lithium disilicate, regardless of milling protocol. Both the fine and extra-fine milling protocols had minimal impact on adaptation, except at the axial wall region, with both protocols promoting adequate results overall.

No abstract available

All-ceramic dental restorations have great advantages, such as highly esthetical properties, a less complex fabrication, and a similar abrasion resistance to enamel. Despite these advantages, ceramic materials are more prone to fracture due to their brittle microstructure. The main aim of this in vitro study was to determine the difference in hot-pressed and milled glass-ceramic mechanical properties such as fracture resistance and microhardness (VHN). Four types of ceramics, two hot-pressed and two milled, feldspathic glass-ceramics and zirconia-reinforced glass-ceramics were selected in this study and tested using the static loading test and Vicker’s testing. Hydrothermal aging, consisting of different baths with temperatures between 5 degrees Celsius and 55 degrees Celsius, was chosen as the in vitro aging method. Statistical analyses are performed using SPSS Statistics software at a significance level of p < 0.05. Micro-hardness values decrease after hydrothermal aging. The static loading test reveals a significant difference between the feldspathic hot-pressed glass-ceramic, which fractures at lower forces, and milled zirconia-reinforced lithium silicate glass-ceramic, which fractures at greater forces (N). Fractographic analysis of the fractured fragments resulted in the static loading test revealing different surface features about the crack origins and propagations under a stereomicroscope.

The aim of this study was to evaluate the topography and the fatigue performance of lithium disilicate glass-ceramic after surface grinding through different laboratory protocols used to simulate the Computer-aided design/Computer-aided manufacturing (CAD/CAM) milling. Ceramic discs (IPS e.max CAD, Ø = 13.5 mm × 1.2 mm of thickness) were produced through different methodologies: milling in CAD/CAM system (CAD/CAM group); produced in-lab with a polished surface (POL group); or produced through in-lab methods and randomly distributed into five groups according to different grinding protocols to simulate the CAD/CAM milling [grinding with a CAD/CAM bur coupled to a mandrel (CAD/CAM Bur group); fine diamond bur using oscillatory movements (DBO group); fine diamond bur in x and y axes of the disc (DBXY group); #60-grit silicon carbide sandpaper (SiC group); and #60-grit wood sandpaper (WS group)]. The specimens were fatigue tested (n = 15) according to the step-stress method (initial load: 60 N; step-size: 20 N; 10,000 cycles/step; 20 Hz frequency). A roughness analysis was performed on all specimens, while fractal dimension (FD) and fractography were performed on representative samples. The Kaplan-Meier analysis showed that the POL (293.3 N) group presented better fatigue performance (higher load and number of cycles for failure) (p < 0.05) than the other groups (CAD/CAM = 222.7 N; CAD/CAM Bur = 181.3 N; DBO = 184.0 N; DBXY = 192.0 N; SiC = 182.6 N; WS = 182.6 N). For roughness, only the SiC (Ra = 1.616; Rz = 10.465) and WS (Ra = 1.673; Rz = 10.655) groups produced statistically similar Ra (μm) and Rz (μm) values to the CAD/CAM (Ra = 1.628; Rz = 9.571) group (p > 0.05). The surface created by CAD/CAM milling and POL group exhibited more complexity (FD) higher values than the experimental groups. For the ceramic surface topography images, the CAD/CAM milling visibly produced a uniform surface compared to the other groups; however, the POL group was the smoothest. The DBO, DBXY, SiC, and WS groups resulted in similar characteristics of surface topography. Therefore, although the SiC and WS groups showed similar roughness to the control group (CAD/CAM), no in-lab simulation method was fully capable to mimic the mechanical performance of the CAD/CAM-milled lithium disilicate glass-ceramic.

This paper reports on the process-fatigue relation of lithium disilicate glass ceramic (LDGC) using low-cycle, high-load Hertzian indentations with a rigid indenter to simulate teeth grinding/clenching of LDGC restorations with different surface asperities obtained in CAD/CAM milling, sintering, polishing and glazing. The maximum contact stresses were evaluated as functions of the number of load cycles and surface treatments using the Hertzian model. Indentation-induced surface damage was viewed using scanning electron microscopy (SEM) to understand the relationships among microstructures, surface asperities, crack morphology and propagation. Different processes and surface treatments significantly affected the maximum contact stresses of indented LDGC surfaces (ANOVA, p < 0.05), which were all significantly reduced with the number of cycles (ANOVA, p < 0.05). Quasi-plastic deformation was dominant in single-cycle indentation of all processed and treated surfaces. In higher cycle indentations, inner cone cracks were formed on all surfaces; median and transverse cracks were formed on the roughest surfaces processed by CAD/CAM milling and sintering. Ring cracks, fretting, pulverization, micro-bridges, surface smearing and wedging, and edge chippings were also propagated on all surfaces. The process-fatigue relation provides an understanding of the mechanical functions of surface asperities produced in different processes and treatments. It indicates that the mechanically assisted growth of surface asperities with different roughness strongly affected the indentation-induced surface damage. Finally, the smoothest surfaces produced by CAD/CAM milling, polishing and sintering sustained the highest contact stresses and the least fatigue damage at higher cycles, ensuring their superior fatigue performance compared to other processed LDGC surfaces.

Background and Objectives: CBCT images have been successfully used for CAD/CAM crown restorations; however, their use for ceramic inlay restorations remains unclear. This study aimed to evaluate the marginal and internal fit of CAD/CAM ceramic inlay restorations fabricated using intraoral scanner, model scanner, and CBCT data. Materials and Methods: Inlay preparations were performed on 11 mandibular molar typodont teeth. The teeth were scanned using an intraoral scanner, an extraoral scanner, and CBCT (0.075 mm voxel size). CBCT-generated DICOM data were converted to STL format with dedicated software. All scan data were transferred to CAD software, and a total of 33 restorations were designed. Feldspathic ceramic blocks were used for milling. Micro-CT was employed to measure marginal and internal gaps, with 60 measurement points taken from three cross-sections per sample. Data were analyzed using ANOVA and Bonferroni tests (p < 0.05). Results: CBCT exhibited greater marginal and internal gap dimensions (mean: 169.27 ± 38.64 μm), which were approximately 60–70 μm higher than those of the intraoral (97.00 ± 10.1 μm) and model scanner groups (109.67 ± 9.72 μm), exceeding clinically acceptable limits (≤120 μm) (p < 0.05). Intraoral and model scanners showed similar, clinically acceptable results. Conclusions: CBCT was less accurate for inlay restorations, likely due to their complex geometry. Nevertheless, fabrication was possible, and further research may improve its clinical applicability.

OBJECTIVES To assess the fatigue behavior of a glass-ceramic and a resin composite milled with two different protocols in a 4-axis milling machine. METHODS Lithium disilicate and resin composite crowns were milled using fine or extra fine mode in a 4-axis machine (n= 15). A full crown molar fiber-reinforced resin epoxy die was scanned and used as substrate. Respective surface treatments were applied, and the restorations were bonded with dual resin cement. Cyclic fatigue test was carried out (20 Hz, initial load 400 N, step size 50 N up to 1500 N, then increased to 100 N with 10,000 cycles per step) to assess the fatigue behavior up to the first crack. All specimens were submitted to a fracture load test until catastrophic fracture. Finite element analysis, topography, and fractography were also conducted. Bur wear was analyzed. Kaplan-Meier and two-way ANOVA tests were carried out to analyze fatigue behavior and fracture load, respectively. RESULTS No significant difference in fatigue behavior was observed between the milling modes for both materials. Resin composite presented a higher survival rate until crack than lithium disilicate. No difference was found in fracture load among the groups. Extra fine milling mode promotes higher bur wear compared to the fine mode. Noticeable contact damage was observed in both materials. SIGNIFICANCE Resin composite crowns exhibit superior fatigue behavior until crack detection compared to lithium disilicate, regardless of the milling mode. No significant difference in catastrophic fracture load was observed between the milling modes or the restorative materials.

The present work aims to develop a production method of pre-sintered zirconia-toughened-alumina (ZTA) composite blocks for machining in a computer-aided design and computer-aided manufacturing (CAD-CAM) system. The ZTA composite comprised of 80% Al2O3 and 20% ZrO2 was synthesized, uniaxially and isostatically pressed to generate machinable CAD-CAM blocks. Fourteen green-body blocks were prepared and pre-sintered at 1000 °C. After cooling and holder gluing, a stereolithography (STL) file was designed and uploaded to manufacture disk-shaped specimens projected to comply with ISO 6872:2015. Seventy specimens were produced through machining of the blocks, samples were sintered at 1600 °C and two-sided polished. Half of the samples were subjected to accelerated autoclave hydrothermal aging (20h at 134 °C and 2.2 bar). Immediate and aged samples were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Optical and mechanical properties were assessed by reflectance tests and by biaxial flexural strength test, Vickers indentation and fracture toughness, respectively. Samples produced by machining presented high density and smooth surfaces at SEM evaluation with few microstructural defects. XRD evaluation depicted characteristic peaks of alpha alumina and tetragonal zirconia and autoclave aging had no effect on the crystalline spectra of the composite. Optical and mechanical evaluations demonstrated a high masking ability for the composite and a characteristic strength of 464 MPa and Weibull modulus of 17, with no significant alterations after aging. The milled composite exhibited a hardness of 17.61 GPa and fracture toughness of 5.63 MPa m1/2, which remained unaltered after aging. The synthesis of ZTA blocks for CAD-CAM was successful and allowed for the milling of disk-shaped specimens using the grinding method of the CAD-CAM system. ZTA composite properties were unaffected by hydrothermal autoclave aging and present a promising alternative for the manufacture of infrastructures of fixed dental prostheses.

PURPOSE This study investigated the in-vitro performance of anterior implant-supported fixed dental prostheses (FDP). The effect of ceramics, fabrication, finalization and the presence of a screw-channel wa s investigated. METHODS Identical anterior ceramic FDPs (tooth 11-13; n=80) were milled (Lithiumdisilicate (LiSiCAD, emaxCAD, Ivoclar-Vivadent), Lithiumaluminiumsilicate (LiAlSi, experimental material) or pressed (Lithiumdisilicate (LiSiPress, emaxPress, Ivoclar-Vivadent), Lithiumsilicate (ZLS, CeltraPress, Dentsply Sirona). FDP-groups (n=8 per material and group) simulated a cemented or screw-retained approach. After cementation or screwing on titanium abutments, thermal cycling and mechanical loading (TCML) was performed on all restorations to mimic 5-year clinical performance. Performance and fracture force were determined and failures were analyzed. STATISTICS (Kolmogorov-Smirnov-test, one-way-ANOVA; post-hoc-Bonferroni, multivariate-regression, α=0.05). RESULTS All FDPs survived TCML without aging, cracks, fractures or chipping. For FDPs without screw channel fracture values varied between with 839.8±112.3N (LiAlSi glazed) and 1485.9±232.6N (LiSiCAD). With screw channel, fracture results varied between 701.4±220.1N (LiALSi glazed) and 1516.3±253.7N (LiSipress). The type of material had a significant influence on the fracture results (LiSi>ZLS>LiAlSi; p≤0.012). Fabrication and finalization had no influence on the results. A screw channel did not significantly (p≥0.135) reduce the fracture force of the FDPs. Type of failure was mostly characterized by a fracture of the connector (LiSi, LiAlSi) or the abutment (ZLS, LiAlSi). CONCLUSIONS FDPs survived TCML without failures indicating that the in vitro performance was not influenced by the tested parameters. Composition of ceramic material has significant influence on the fracture resistance of implant supported LiSi based FDPs. Screw channel, fabrication or finalization did not weaken the FDPs.

AIM The aim of this randomized, prospective, and clinical multicenter study was to compare the overall clinical performance of two restorative options over a 5-year period: individualized CAD/CAM abutments veneered with a hand-layered ceramic, and prefabricated zirconium dioxide abutments veneered with press ceramic and inserted into a single edentulous gap in the anterior maxilla. MATERIALS AND METHODS Forty subjects were recruited from two universities: 20 from the University of XX and 20 from the University of XY. Each subject received an implant to restore a single edentulous gap in the maxillary anterior region (14-24 FDI). 20 patients were randomized into each Group. Group A received a one-piece single crown produced from a prefabricated zirconia abutment with pressed ceramic and Group B received an individualized CAD/CAM zirconia abutment with a hand-layered technique. After 5 years, the aesthetic and radiographic parameters were assessed. RESULTS Group A had four dropouts and one failure, resulting in a 95% survival rate and 95% success rate. Group B had two dropouts and two failures which resulted in a 90% survival rate and 90% success rate. No crestal bone level changes were observed, with a mean DIB of 0.06 mm in Group A and 0.09 mm in Group B. No statistically significant differences were present at baseline, 6 months, 1 year, 3 years, or 5 years for DIB values between time points and groups. Pink aesthetic score/white aesthetic score, Peri-Implant and Crown Index, and Implant Crown Aesthetic Index values were stable over time at all five points for both groups. CONCLUSION Both implant-supported restorative options represent a valuable treatment option for the restoration of implant crowns in the anterior maxilla. CLINICAL SIGNIFICANCE In general, the use of ceramic abutments in the anterior zone represents a valuable treatment procedure with both standardized and CAD/CAM individualized abutments and following the recommendations from the respective manufacturer(s).

Introduction: There is an increasing number of optical intraoral scanners (IOSs) that are based on different scanning technologies; the choice of which may affect clinical use. Aim: To investigate the marginal integrity and internal fit of CAD/CAM ceramic crowns constructed using three different (IOSs)with one milling CAM unit. Material & methods: 18 white epoxy resin dies were duplicated from a prepared maxillary first premolar tooth and divided into groups A, B, and C (n=6). Group A dies were scanned with Sirona Omnicam (IOS). Group B dies were scanned with Trios 3Shape (IOS), and group C dies were scanned with Emerald PlanScan (IOS). All dies received standardized Emax CAD crowns milled by Inlab MC X5 milling machine and were fired for crystallization and glazing in Programat p 310 ceramic furnaces. Vertical marginal gaps were measured. All crowns were cemented using Theracem resin cement. Internal fit was measured by sectioning half of the cemented crowns in a bucco-lingual direction and the other half in a mesio-distal direction. Data analysis was performed using 2way-ANOVA and paired t-test at 0.05 using IBM SPSS version 29.0. Results: There was a statistically significant difference in mean vertical marginal gap among the three groups ( p ≤ 0.05). The highest values were reported by Group C followed by group B. The lowest values were reported by group A. The mean internal gap of group C was significantly lower than other groups, while there was no statistically significant difference between mean internal gap of group B & group A. Conclusion: All tested (IOSs) proved to produce clinically acceptable ceramic restorations in terms of marginal and internal adaptation. Difference of scanning technologies of IOSs was found to affect significantly marginal and internal adaptation of the CAD/CAM ceramic crowns.

Background. This study aimed to evaluate the final color of restorations with three different core materials (Co–Cr, Zirconia, and PEEK) veneered with heat-pressed ceramic or CAD/CAM composite. Methods. Forty cores in the form of square with dimensions of 10 × 10 mm and thickness of 0.5 mm were milled from Zirconia and Co–Cr blocks and were veneered with either A2 shade CAD/CAM composite resin or heat-press ceramic (n = 10). Ten samples from polyetheretherketone blocks were only veneered with composite resins. A2 shade veneer material with 2 mm served as control for color evaluation of samples. Color parameters were measured by spectrophotometer. The data were analyzed using one-way ANOVA and Tukey’s post hoc test. Results. The mean color differences between Co–Cr, Zirconia and PEEK samples veneered with composite and the control sample were 2.91 (±0.45), 3.24 (±0.33), and 2.75 (±0.35) and for Co–Cr and Zirconia in ceramic groups were 6.46 (±0.32) and 1.97 (±0.19), respectively. One-way ANOVA and Tukey’s post hoc test showed a significant difference between the core groups veneered with ceramic ( P ≤ 0.001 ). The type of core material in the composite veneered samples, however, did not make a significant difference ( P = 0.186 ). All groups except for Co–Cr-ceramic showed clinically acceptable results (ΔE < 3.7). Conclusion. Type of core material presented significant effect on the final color of restorations when ceramic was used as a veneer material. Conversely, the final color of composite veneer restorations is not affected by the core type. CAD/CAM composites can provide adequate color coverage for different core materials without exceeding a minimum clinically acceptable thickness.

Marginal fit of the dental restoration is important to prevent microleakage and periodontal problems so as to avoid secondary caries around the abutment teeth. The purpose of the study was to compare and evaluate the internal fit of copings manufactured using a CAD/CAM-system and laboratory-made heat-pressed ceramics. For this research, typodont mandibular left first molar was prepared about 1.5mm occlusal reduction and 6˚ taper both mesiodistally and buccolingually with shoulder finish line of 1.0mm width to receive all ceramic crown which was duplicated in silicone impressions and the respective working casts were formed using Type IV die stone and the restorations were made by CAD-CAM system for zirconia coping and wax pattern for heat-pressable lithium disilicate ceramics. Total of 20 dies were made and divided into Group I- zirconia copings and Group II - heat pressable lithium disilicate ceramics, in which 10 crowns were made in each group. The crowns were cemented to the respective dies with cyanoacrylate cement using finger pressure. The samples were then sectioned facio-lingually and the three zones measured were 2mm above the marginal finish line in both lingual and buccal side and one in the center of the occlusal surface. The mean horizontal and the vertical internal adaptation discrepancies statistically analyzed using Mann-Whitney test. It was concluded that CAD-CAM milled zirconia copings showed closer adaptation in the axial walls than heat pressed ceramic copings. But in the mid occlusal level where the adaptation was closer in heat pressed ceramic copings than the CAD-CAM milled zirconia copings.

The aim of this case report was to demonstrate the clinical and laboratory workflow for the fabrication of a zirconia-ceramic bridge in the anterior region of the maxilla using CAD/CAM technology (KaVo Everest system). The patient had lost a central incisor due to a vertical root fracture, and after analyzing various treatment options, the fabrication of an all-ceramic bridge was selected. The clinical procedure included precise tooth preparation according to the principles of periodontal preservation and structural stability, application of the double-cord technique for optimal gingival retraction, and corrective impression-taking using addition silicones. The laboratory procedures involved the fabrication of a scanned working model, virtual design of the bridge framework in 3D CAD software and milling of the framework from a soft zirconia-oxide block. Additional coloration and sintering were performed to achieve a high level of esthetic quality. The final prosthetic restoration was completed with veneering ceramic layering, with shade determination using a combination of a classical shade guide and a digital Spectroshade device. It was concluded that the use of CAD/CAM technology enables high precision, material biocompatibility, and superior esthetic outcomes while significantly reducing laboratory processing time, highlighting the importance of integrating digital technologies into contemporary prosthodontic practice. Keywords: CAD/CAM, zirconia-ceramic, prosthodontics.

The present research aimed to assess the impact of endodontic access cavity preparation on the fracture resistance of CAD-CAM crowns. A total of 40 extracted human upper first premolars were utilized in present research. All premolars were affixed in epoxy resin blocks, prepared by utilizing a CNC milling machine to receive full coverage ceramic crowns, and evenly split into two primary groups based on the type of ceramic; Group LD: teeth restored with lithium-disilicate (LD) crowns, and Group PIC: teeth restored with polymer-infiltrated ceramic (PIC) crowns. Every group was subdivided into 2 subgroups (n=10); Subgroup LDI: Intact LD crowns, Subgroup LDR: Repaired LD crowns, Subgroup PICI: Intact vita PIC crowns, and Subgroup PICR: Repaired PIC crowns. Crowns were cemented using Calibra Universal resin cement. The repaired subgroups received a standardized access cavity at the center of the occlusal surface and then repaired with direct composite resin. All samples were exposed to thermo-mechanical loading in a chewing simulator for 118,000 cycles, loaded until failure, and then statistically analyzed. For intact control subgroups, the greatest mean scores were showed in PICI (1308.71±244.15 N) compared to LDI (1154.38±133.83 N), and the variation was not statistically significant (P=0.097). For repaired subgroups, the highest mean values were recorded for PICR (727.84±240.52 N) compared to LDR (707.03±298.28 N), and the variation was not statistically significant (P=0.866). Both LD and PIC crowns perform the same after exposure to an endodontic access cavity, suggesting their repairability and useability.

PURPOSE The success of removable partial dentures (RPDs) depends on well-designed abutments or surveyed crowns. Advances in computer-aided design and computer-aided manufacturing (CAD-CAM) technology have made all-ceramic materials viable alternatives to traditional ceramo-metal surveyed crowns, but their performance, particularly regarding internal fit and fracture resistance, requires further studies, especially with different rest seat preparations simulated on the abutment dies. This study evaluated the internal fit and fracture resistance of CAD-CAM ceramic crowns with wide and narrow rest seat designs to assess their potential as surveyed crowns for RPDs. MATERIALS AND METHODS Sixty mandibular premolar abutment dies were modified to simulate narrow and wide occlusal relief designs and were divided into six groups based on the design (wide/narrow) and material type: force-absorbed hybrid ceramics (HC), zirconium lithium silicate (ZLS), and lithium disilicate glass-ceramic (LDC). CAD-CAM ceramic crowns were fabricated, milled, and analyzed for internal fit using Geomagic Control X software. Fracture resistance in newton (N) was tested using a universal testing machine. Scanning electron microscopy (SEM) was employed to examine fracture morphology. Statistical analyses included two-way analysis of variance (ANOVA) and post hoc Tukey's test (α = 0.05). RESULTS The LDC group had the highest fracture resistance, while ZLS and HC showed no significant difference [F(2) = 10.523, p < 0.001]. Internal fit did not significantly differ between materials [F(2) = 0.381, p = 0.686], though LDC had a slightly larger internal gap. Rest seat design significantly affected both fracture resistance and internal fit [F(1) = 68.581, p < 0.001; F(1) = 11.185, p = 0.002], with wide designs showing higher fracture resistance and narrow designs having larger internal gaps. SEM revealed crack propagation originating from rest seat bases, with longer crack lines observed in wide rest designs. CONCLUSION Rest seat design significantly influences the fracture resistance and internal fit of CAD-CAM ceramic crowns. Wide rest seat designs provide superior fracture resistance compared to narrow designs, while narrow seats exhibit larger internal gaps, potentially compromising restoration longevity.

This study investigates light transmission through five types of computer‐aided design/computer‐aided manufacturing (CAD/CAM) lithium disilicate ceramics, varying in thickness (0.50, 1.00, and 1.50 mm). A total of 150 specimens (10 per group) were fabricated using both traditional and novel ceramic materials: E.max CAD (traditional), n!ce Straumann and LiSi Block GC (fully‐crystallized), and Amber Mill and Cerec Tessera (precrystallized). After polishing, light transmission was measured using a curing radiometer and surface microstructures were examined with scanning electron microscopy (SEM). The data were analyzed using two‐way analysis of variance (ANOVA) with Tukey’s post hoc tests. Results revealed that light intensity decreased as the ceramic thickness increased, regardless of the material type. Amber Mill (0.50 mm) exhibited the highest light intensity at 537 mW/cm2, followed by E.max CAD (475 mW/cm2) and n!ce Straumann (470 mW/cm2). In contrast, LiSi Block GC (1.50 mm) showed no light transmission (0 mW/cm2), with Cerec Tessera (60 mW/cm2) and E.max CAD (175 mW/cm2) also exhibiting low transmission at 1.50 mm. SEM analysis identified structural differences among the materials. These findings suggest that both the composition and thickness of CAD/CAM lithium disilicate ceramics significantly impact light transmission. Results revealed that material composition and thickness significantly influenced light transmission values, underscoring the importance of selecting appropriate ceramic type and thickness to optimize polymerization during light‐cured resin cementation in clinical practice.

To compare and assess the fracture strength of indirect overlay restorations bonded using various bonding techniques: sonically activated composite materials, preheated composite materials, and adhesive resin cement. The restorations were fabricated utilizing two distinct categories of all-ceramic CAD/CAM materials: reinforced resin composite blocks and lithium disilicate blocks. Depending on the CAD/CAM block type utilized for constructing the indirect overlay restorations, two main groups of 24 teeth each were created from the 48 human maxillary first premolar teeth that were ready for restorations. Group A consisted of indirect overlays made of lithium disilicate (IPS e.max CAD) blocks, whereas Group B used reinforced resin blocks (BRILLIANT Crios) for indirect overlays. subsequently according to the type of cement utilized in cementation. After the prepared teeth were scanned using the CEREC Omnicam digital intraoral scanner, indirect overlay restorations were designed utilizing CEREC Premium programme (version 4.4.4), and additional milling was carried out using the CEREC MC XL milling device. A computer-controlled universal testing machine (LARYEE, China) was then used to apply compressive axial loads to all cemented indirect overlay restorations at a crosshead speed of 0.5 mm/min till occurrence of fracture. A Student's t-test, LSD test, and one-way ANOVA test were utilized to analyze the data at a significance level of 0.05.  This in vitro investigation revealed the greatest fracture strength mean value in the indirect overlays cemented with resin cement compared to other types of cement, regardless of the CAD/CAM block type. Depending on the findings of this research, regardless of the cement type, the mean fracture strength values of the indirect overlays made from both CAD/CAM blocks exceed the maximum biting force in the premolar area, indicating that both block types may be utilized clinically as overlay restorations in the premolar area.

PURPOSE To investigate the effect of recycling of lithium disilicate (LD), surface treatment and thermocycling (TC) on the bond strength (SBS) to resin cement. MATERIALS AND METHODS Blocks of LD were made according to the recycling cycle, with 24 blocks for each strategy: Control-conventional sintering; 1R (1 recycling cycle) and 3R (3 recycling cycles). For the recycling groups, blocks were waxed (10x10x3mm), mounted in a silicone ring, poured with investment material, and then residues of sintered LD blocks were pressed by the lost wax technique. The residual LD was reused as described until reach 3R. Afterwards, the blocks were embedded in acrylic resin, sanded and divided (n=15) according to the factors "surface treatment" (HF20s+Silane and HF120s+Silane and Monobond Etch&Prime- MEP) and TC (with/10.000 cycles and without). After surface treatment, cylinders (Ø:2mm) of resin cement were made and submitted to SBS test (100KgF,1mm/min). Data (MPa) were analyzed by 3-way ANOVA, Tukey's test (5%) and Weibull analysis. Failure analysis was performed with stereomicroscope. RESULTS ANOVA revealed that all factors were significant (P=.000*). The group 3RMEP(105.09±19.49) presented the highest SBS among the experimental groups. 1RHF20sTc(7.50±1.97) group had the lowest SBS, similar to the CHF20sTc(15.69±3.77), 1RHF20s(15.12±3.03), 1RHF120sTc(14.60±3.43) and 3RHF20sTc(15.65±0.97). The Weibull modulus and characteristic strength varied among the experimental groups (P=0.0). Failure analysis revealed adhesive and mixed types. CONCLUSION The recycling of DL ceramics increases the SBS to resin cement when the ceramic is treated with HF120s+S or MEP.

PURPOSE The purpose of this in vitro study was to compare the tensile bond strength (TBS) of resin nanoceramics (RNC), zirconia, and lithium disilicate (LS2) restorations cemented to titanium abutments before and after thermomechanical aging. MATERIALS AND METHODS Twelve specimens per group were fabricated to determine the TBS between a titanium abutment and 4 types of crown materials (2 RNCs, LS2, and translucent zirconia crowns for the maxillary molar). After milling, the abutments and crowns were cemented with resin cement after air-particle abrasion. In addition, thermomechanical aging (200,000 cycles, 50 N, 2 Hz) was applied to half of the specimens by using a mastication simulator. TBS was measured by using a universal testing machine. The interface between the crown and the cement was observed by using scanning electron microscopy (SEM). Two-way ANOVA was performed to analyze the effects of crown materials and thermomechanical aging. Failure-mode and interface analyses were also conducted. RESULTS After thermomechanical aging, the TBS decreased in the LS2 specimens and increased in RNCs (p < 0.001). The ratio of mixed failure and debonding with the hole-sealing resin increased in the RNC group. SEM images showed the reduced gap between the crown and the resin cement after thermomechanical aging in the RNC group. CONCLUSIONS Differences in TBS were affected by the crown materials after thermomechanical aging. After thermomechanical aging, the RNC crowns showed increased TBS, whereas LS2 and zirconia crowns exhibited decreased or similar TBS. This article is protected by copyright. All rights reserved.

STATEMENT OF PROBLEM Computer-aided design and computer-aided manufacturing (CAD-CAM) materials are available for different types of restorations. However, the longevity of the material is affected by chipping, milling damage, flexural strength, and surface roughness, and a standard edge chipping test or standardized measurements are unavailable for monitoring edge chipping of rotary instrument-milled materials. PURPOSE The purpose of this in vitro study was to analyze the surface roughness and edge chipping of different CAD-CAM diamond rotary instrument-milled dental material bars, correlate the effect of machining damage with material strength, and compare the flexural strength of rotary instrument-milled and sectioned CAD-CAM blocks. MATERIAL AND METHODS Five dental CAD-CAM materials were tested: lithium disilicate glass-ceramic (IPS e.max CAD), leucite-reinforced glass-ceramic (IPS Empress CAD); feldspathic porcelain (Vitablocs Mark II); feldspar ceramic-polymer infiltrated (Enamic), and composite resin (Lava Ultimate). Rectangular bars were designed and milled for each material (n=10). The surface roughness of the bars was measured using a profilometer. All edges of 3 selected bars were analyzed with scanning electron microscopy (SEM) for the chip length, depth, and area. The 3-point bend test was used to test the flexural strength of rotary instrument-milled and saw-cut bars with the same dimensions. Analysis of variance and the Tukey honestly significant difference post hoc test were used to determine the difference among the groups (α=.05). RESULTS IPS e.max CAD had the highest surface roughness and Lava Ultimate the lowest. Lava Ultimate had the smallest chipping factor and IPS Empress CAD the largest. The surface location significantly affected the chipping depth, area, and length (P<.05). A strong correlation was found between the decrease in flexural strength and the chipping length on the central tensile side of the rotary instrument-milled materials (R2=.62, P=.01), as well as the chipping depth (R2=.44, P=.01). CONCLUSIONS Edge chipping was significantly associated with the material type, milling surface, and edge location and strongly correlated with a decrease in flexural strength.

Introduction: This study aims to determine and compare the fracture strength and failure modes of zirconia-reinforced lithium silicate glass ceramics (ZLS) and yttria-stabilized zirconia-based ceramic MOD and MO inlay restorations. Materials and Methods: Stumps representing the maxillary second premolar were prepared using HyperDent software and CAD/CAM milling units. Thirty-two epoxy resin die models were obtained, with 16 samples in each group. Subsequently, restorations were fabricated using Vita Suprinity (VITA Zahnfabrik, Bad Sackingen, Germany) and IPS e.max ZirCAD CAD/CAM (Ivoclar et all., Liechtenstein) blocks to restore the inlay cavities. The specimens were subjected to aging and then tested for fracture using a universal testing machine. The resulting fractures were classified. Data normality was assessed using the Shapiro-Wilk test, and homogeneity of variances was evaluated using the Levene test. The interaction between restorative material type and cavity surface was tested using two-way ANOVA. Results: The fracture strength of IPS e.max ZirCAD material (mean value: 723.18±57.51) is higher than that of Vita Suprinity ZLS material (689.86±113.61), but this difference is not statistically significant (F=3.46, p=0.073). The group with 3-surface cavities in the tooth material (768.00±60.60) has significantly different fracture strength compared to the group with 2-surface cavities (645.037±71.20) (F=47.18, p<0.001). Conclusions: Having a 3-surface cavity may further enhance the fracture resistance of inlay restorations, and this difference is statistically significant. There is no significant difference in fracture strength among restorative materials.

OBJECTIVE To evaluate the effect of the deterioration of computer aided design/computer aided manufacturing (CAD/CAM) burs during zirconia milling, on surface roughness, contact angle, and fibroblast viability. MATERIALS AND METHODS Ceramic blocks were milled and 75 ceramic disks (8 × 1.5 mm) made and allocated into three groups (n = 25): G1-brand new 2L and 1L burs, G2-2L bur at the end of lifetime and brand new 1L bur and G3-both burs at the end of their lifetimes. Roughness (Ra, Rq, and Rz) was evaluated using a 3D optical profilometer, the contact angle by the sessile drop method and the cell viability of the mouse NIH/3T3 fibroblast, using the Alamar Blue assay at intervals of 24, 48, and 72 h (ISO 10993-5). Data were analyzed by one-way ANOVA and Kruskal-Wallis tests (p ≤ 0.05). RESULTS Roughness increased as the burs deteriorated and G3 (0.27 ± 0.04) presented a higher value for Ra (p < 0.001). The highest contact angle was observed in G3 (86.2 ± 2.66) when compared with G1 (63.7 ± 12.49) and G2 (75.3 ± 6.36) (p < 0.001). Alamar Blue indicated an increase in cell proliferation, with no significant differences among the groups at 24 and 72 h (p > 0.05). CONCLUSIONS The deterioration of the burs increased the surface roughness and decreased the wettability, but did not interfere in cell viability and proliferation. CLINICAL SIGNIFICANCE The use of custom zirconia abutments represents an effective strategy for single crowns restorations. Our findings suggest that these abutments can be efficiently milled using CAD/CAM burs within their recommended lifetime.

(1) The aim of this in vitro study was to investigate the handling of proximal-cervical undermined enamel margins on the adhesive performance of differently fabricated and differently cemented ceramic inlays and partial crowns (2) Methods: 192 extracted third molars received MOD (n = 96) and partial crown (n = 96) preparations. A mesial 2 × 2 × 4 mm cervical groove was created in dentin to simulate a deeper (dentin) caries excavation. This dentin groove was either left (G/groove), filled with composite (F/filling), or completely removed (D/dentin). Distal proximal boxes did not receive a groove and served as controls within the same tooth. Labside (e.max Press) restorations additionally went through a temporary phase. Labside and chairside (e.max CAD) inlays and partial crowns were then adhesively luted with Syntac/Variolink Esthetic (SV) or Adhese Universal/Variolink Esthetic (AV). Initially, and again after thermomechanical loading (TML: 1 million cycles at 50 N, 25,000 thermocycles at 5 °C/55 °C), specimens were molded and the resulting 24 groups of epoxy replicas (n = 8) were gold-sputtered and examined for marginal gaps using scanning electron microscopy (200× magnification). Light microscopy (10× magnification) was used to measure proximal cervical crack propagation in adjacent enamel. (3) Results: Regardless of the adhesive system, D groups generally showed significantly lower marginal quality (79–88%; p < 0.05), with the universal adhesive performing better than the multi-step adhesive system (p < 0.05). Subgroups G and F were similar in marginal quality (94–98%; p > 0.05) and not worse than the controls (p > 0.05) regardless of the adhesive system, but showed less cracking in F than in G (p < 0.05). In general, fewer cracks were observed in chairside CAD/CAM restorations than in laboratory-fabricated restorations (p < 0.05). Partial crowns showed better marginal quality (96–98%) and less cracking than inlays (p < 0.05). (4) Conclusions: If the dentin level is lower than the enamel level in ceramic preparations after caries excavation in the proximal box, the resulting undermined enamel should not be removed. In terms of enamel integrity, partial crowns outperformed inlays.

No abstract available

Objectives: The aim of this study intended to evaluate the effect of various surface treatments on the adhesion of CAD/CAM fabricated Y-TZP ceramic onlays. Materials and methods: Forty-eight, cracks-free extracted human molars have been acquired in the study. The specimens have been divided randomly according to surface treatment of Zirconia into four main groups of twelve specimens each as follows (n=12): group1: tribochemical silica coating; group 2: sandblasting; group 3: sandblasting with primer; and group 4: sandblasting and laser with primer. The first half of the specimens were put through the tests right away, whereas the other half were put through the tests after being subjected to thermo-mechanical cyclic stress. Buehler Isomet 4000 Cutting Machine (IsoMetTM 4000, Buehler Ltd, Lake bluff, LL, USA) was used for the preparation of standardized onlays cavities. Then micro-tensile bond strength test μTBS was performed. Data were statistically analyzed using the Shapiro-Wilk, post hoc-Tukey, student t-test, and one-way ANOVA tests. Results: The outcome of the study revealed statically significant differences in μTBS between all groups. The most favorable bonding was in the group of sandblasting with primer (12.50 ± 2.40) and the least was with the tribochemical silicoating (3.70 ± 0.96) (P=0.002). Conclusions: Within the parameters of this study, the different surface treatments had a significant difference in μTBS. Sandblasting with primer consider the most favorable outcome of the current study. However, thermomechanical cyclic loading deteriorates the bond strength when using sandblasting alone.

STATEMENT OF PROBLEM Resin-bonded prostheses, including interim resin-bonded prostheses, are effective in preserving tooth structure compared with other types of fixed dental prostheses for the replacement of missing teeth. However, loss of retention remains a notable concern with these types of prostheses. PURPOSE The purpose of this in vitro study was to investigate the influence of glass-ceramic type, resin type, and surface finish on the shear bond strength (SBS) to the CAD-CAM ceramics used to fabricate interim resin-bonded prostheses. MATERIAL AND METHODS Eighty 10×2-mm glass-ceramic disks were fabricated by using a diamond saw (IsoMet 1000), 40 from feldspathic porcelain blocks (Vita Mark II) and 40 from lithium disilicate blocks (IPS e.max CAD). Half of the specimens in each group were left with a dull or matte surface finish after cutting, while the other half were glazed with an add-on glaze (VitaAkzento Plus Glaze Spray and IPS e.max CAD Glaze Spray, respectively). The disks were mounted in acrylic resin, and each group was subdivided into 2, with 1 receiving a photopolymerized resin cement (RelyX Veneer) and the other receiving a flowable composite resin (Filtek Supreme Ultimate Flow) to form 2.38×2-mm cylinders. SBS was determined using a universal testing machine (Instron 4411) in accordance with the International Organization for Standardization (ISO) 29022:2013 standard, and failure modes were analyzed by using a stereomicroscope with ×40 magnification. The data were analyzed with a 3-way analysis of variance and Tukey post hoc analysis. The chi-squared test was used to analyze the failure mode (α=.05 for all tests). RESULTS Ceramic type, resin type, and surface finish significantly impacted SBS (P<.001, P=.003, P<.001, respectively). Lithium disilicate showed higher SBS than feldspathic porcelain, and flowable composite resin exhibited higher SBS than resin cement. Glazed surfaces displayed lower SBS compared with the dull or matte surfaces. The combinations among the 3 materials also impacted SBS (P=.03). In addition, the combinations between ceramic type and surface finish affected SBS (P<.001), regardless of resin cement type. No other combinations affected the SBS (P>.05). The mode of failure was different among the groups (P<.001). In comparison with all other groups, cohesive failures were most prevalent in feldspathic porcelain with a dull or matte surface finish, regardless of the resin type used. CONCLUSIONS The SBS to glass-ceramics was influenced by ceramic material, resin cement type, and surface finish. Flowable composite resin showed higher SBS than resin cement. A dull or matte surface finish exhibited greater bond strength than a glazed surface. Lithium disilicate had higher SBS than feldspathic porcelain.

Aims: The aim of this study is to investigate the color changes of three different traditional composites, one ceramic and two resin-based composites CAD/CAM blocks in different solutions. Methods: The materials used in the study were CAD/CAM block containing lithium disilicate glass ceramic (Ivoclar), Vita Enamic containing resin (VITA), Lava Ultimate Block containing resin (3M ESPE), G-aenial anterior composite (GC,), Filtek™ Ultimate Universal composite (3M ESPE) and Clearfil Majesty Esthetic composite (Kuaray). As colouring solutions, red wine (Buzbaǧ), black tea (Lipton), coffee (Nescafe) and distilled water (EAU distillee) were used. For the preparation of the traditional composite samples to be used in the study, 7 × 7 mm square-shaped plexiglass moulds, 1.2 mm in thickness, were used. The CAD/CAM blocks with ceramic and resin content were cut at the same thickness using a Struers sensitive cutting device. The samples were then randomly separated into grups of 10 and of the 240 samples, groups were separated into 6 different materials and 4 different solutions. The colour measurements of the 240 samples were taken at baseline, 30 days and 120 days with a Lovibond spectrophotometer (Tintometer). Results: A statistically significant difference was determined between the materials in respect of the ΔE values in the 30-day solution groups (P < 0.05). No statistically significant difference was determined in the ΔE values of the different materials in the 30-day and 120-day distilled water groups (P > 0.05). A statistically significant difference was determined between the materials in respect of the ΔE values in the 120-day solution groups (P < 0.05). Conclusion: In respect of discolouration, ceramic blocks are more successful. Resin-based blocks and traditional aesthetic composites showed more discolouration. The dietary habits of the patient should be taken into consideration in the selection of the restorative material.

STATEMENT OF PROBLEM High-translucency ceramics can be influenced by the underlying structure, altering the restoration shade. How this affects color matching is unclear. PURPOSE The purpose of this in vitro study was to investigate the optical effects of cement shade, ceramic type, ceramic thickness, and abutment material on the final color of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramic restorations. MATERIAL AND METHODS Two shades of resin cement (yellow, translucent), 3 types of background (titanium, white zirconia, yellow zirconia), and 3 types of high-translucent ceramic (each type shade A1 and A3) were used in this study. For the experimental groups, a total of 72 ceramic specimens were produced across 4 groups based on ceramic thickness (1.0 mm, 1.5 mm, and 2.0 mm). For the control groups, each ceramic type and shade was prepared at a thickness of 4 mm. A total of 8 resin cement specimens were produced in 4 groups based on shade by using a plastic mold (12×12×0.2 mm). To demonstrate the effect of implant abutment materials, 3 types of background were fabricated with a thickness of 2 mm. For the experimental groups, 3 specimens (ceramic, cement, and background) were sequentially placed with glycerin in the center of each background specimen. Color measurements of the experimental groups were made with a spectrophotometer and recorded in the Commission Internationale de l'Eclairage Lab coordinate system. The color differences (ΔE) between experimental and control groups were then calculated. The Kruskal-Wallis test (α=.05) was used to analyze the multiple comparisons of ceramic thickness, ceramic type, and abutment material. The Mann-Whitney U test (α=.05) was used to analyze cement shade. RESULTS Significant differences were found for different ceramic thicknesses, ceramics types, and abutment materials (P≤.001). A clinically acceptable shade (ΔE≤3) was found in 1.5- and 2.0-mm ceramics with the titanium and 2.0-mm ceramics with the yellow zirconia background. However, the color between the experimental group and the control group was similar when using the 2 cement shades (P>.05). CONCLUSIONS An increase in ceramic thickness could minimize alteration of the final shade. High-translucency ceramics, together with a resin cement, were able to successfully mask titanium with a ceramic thickness of at least 1.5 mm. However, only a ceramic with a thickness of 2.0 mm was able to mask the yellow zirconia background.

OBJECTIVES This study aimed to assess the surface roughness, surface free energy (SFE), and shear bond strength (SBS) on a lithium disilicate glass-ceramic surface following varying etching protocols (time variation) and application of silane either with or without adhesive material. METHODS AND MATERIALS Lithium disilicate glassceramic (LDGC) computer-aided design and computer-aided manufacture (CAD/CAM) blocks were cut using a slow-speed cutting mechanism. CAD/CAM blocks were then evaluated for surface roughness, 6 groups (n=20); SFE,12 groups (n=5); and SBS, 10 groups (n=10). The cut CAD/CAM blocks were randomly allocated to 28 groups. Groups were based on the following: 30 or 90 seconds of etching with 9% hydrofluoric acid (HF); application or absence of silane coupling agent (Sil); and application or absence of adhesive (Adh).The control group (Cont) had untreated surfaces. Unetched surfaces were surveyed with only silane (Sil), only adhesive (Adh), or silane+adhesive (SilAdh). Further etched groups were HF30 with HF for 30 seconds, HF30-Sil, HF30-Adh, and HF30-SilAdh. Alternative 90-second etching times produced similar groups: HF90, HF90-Sil, HF90-Adh, and HF90-SilAdh. A digital profilometer was used to assess the surface roughness of specimens, and two readings were recorded. Sessile drop analysis was used to examine SFE specimens, and the OWRK model was modified to measure liquid surface tension. A universal testing machine (UltraTester, Ultradent Products, Inc, South Jordan, UT, USA) was utilized for the SBS test, with the crosshead speed set at 0.5 mm/min until failure. Representative treated specimens from each group were submitted to surface morphological evaluation and chemical analysis using scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDXS) (n=3). After data collection, evaluation using one- or two-way analysis of variance and the post-hoc Tukey test (α=5%) was conducted. RESULTS A longer etching time of 90 seconds produced a rougher surface. After the 90-second etching process, SFE displayed the greatest values; nevertheless, the use of silane did not affect SFE. For every group examined, the application of silane followed by adhesive resulted in an increase in SBS and more stable bonding over time. SEM/EDXS showed that etching times did affect the amount of cerium on the surface and altered surface morphology. CONCLUSIONS Higher and more consistent bond strengths have been observed with longer etching periods. Silane and adhesive application on the ceramic surface showed stronger and enhanced bond strength, specifically when longer etching times were employed.

Computer-aided design (CAD)/computer-aided manufacturing (CAM) milling and handpiece grinding are critical procedures in the fabrication and adjustment of ceramic dental restorations. However, due to the formation of microfractures, these procedures are detrimental to the strength of ceramics. This study analyzes the damage associated with current brittle-regime grinding and presents a potential remedy in the application of a safer yet still efficient grinding regime known as “ductile-regime grinding.” Disc-shaped specimens of a lithium disilicate glass-ceramic material (IPS e.max CAD) were obtained by cutting and crystallizing the lithium metasilicate CAD/CAM blanks (the so-called blue blocks) following the manufacturer’s instructions. The discs were then polished to a 1 µm diamond suspension finish. Single-particle micro-scratch tests (n = 10) with a conical diamond indenter were conducted to reproduce basic modes of deformation and fracture. Key parameters such as coefficient of friction and penetration depth were recorded as a function of scratch load. Further, biaxial flexure strength tests (n = 6) were performed after applying various scratch loads to analyze their effects on ceramic strength. Scanning electron microscopy (SEM) and focused ion beam (FIB) were used to characterize surface and subsurface damage. Statistical analysis was performed using one-way analysis of variance and Tukey tests. While the SEM surface analysis of scratch tracks revealed the occurrence of both ductile and brittle removal modes, it failed to accurately determine the threshold load for the brittle–ductile transition. The threshold load for brittle–ductile transition was determined to be 70 mN based on FIB subsurface damage analyses in conjunction with strength degradation studies. Below 70 mN, the specimens exhibited neither strength degradation nor the formation of subsurface cracks. Determination of the brittle–ductile thresholds is significant because it sets a foundation for future research on the feasibility of implementing ductile-regime milling/grinding protocols for fabricating damage-free ceramic dental restorations.

The use of dental resin composites adapted to computer-aided design/computer-aided manufacturing (CAD/CAM) processes for indirect tooth restoration has increased. A key factor for a successful tooth restoration is the bond between the CAD/CAM composite crown and abutment tooth, achieved using resin-based cement. However, the optimal pairing of the resin cement and CAD/CAM composites remains unclear. This study aimed to identify the optimal combination of a CAD/CAM composite and resin cement for bonding. A commercial methyl methacrylate (MMA)-based resin cement (Super-Bond (SB)) and four other composite-based resin cements (PANAVIA V5; PV, Multilink Automix (MA), ResiCem EX (RC), and RelyX Universal Resin Cement (RX)) were tested experimentally. For the CAD/CAM composites, a commercial polymer-infiltrated ceramic network (PICN)-based composite (VITA ENAMIC (VE)) and two dispersed filler (DF)-based composites (SHOFU BLOCK HC (SH) and CERASMART300 (CE)) were used. Each composite block underwent cutting, polishing, and alumina sandblasting. This was followed by characterization using scanning electron microscopy, inorganic content measurement, surface free energy (SFE) analysis, and shear bond strength (SBS) testing. The results demonstrated that the inorganic content and total SFE of the VE composite were the highest among the examined composites. Furthermore, it bonded highly effectively to all the resin cements. This indicated that PICN-based composites exhibit unique bonding features with resin cements. Additionally, the SBS test results indicated that MMA-based resin cement bonds effectively with both DF- and PICN-based composites. The combination of the PICN-based composite and MMA-based resin cement showed the best bonding performance.

STATEMENT OF PROBLEM Applying stains to the intaglio surface of computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic ceramic restorations has been proposed as an option to help mask darkened substrates. However, little is known about the effects of this procedure on the adhesion between the resin cement and the ceramic. PURPOSE The purpose of this in vitro study was to evaluate the effect of intaglio surface staining on the microshear bond strength between 2 CAD-CAM ceramics and a resin cement. MATERIAL AND METHODS Lithium disilicate (Gmax) and leucite-reinforced (Gpress) ceramic blocks were sectioned, crystalized when indicated, and polished. They received either none, 1, or 2 layers of ceramic stains and a glaze liquid mixture followed by a firing cycle. The surfaces of groups Gmax0, Gmax1, and Gmax2 were etched with 9% hydrofluoric acid etching (HF) for 20 seconds, and those of groups Gpress0 and Gpress1 were etched for 60 seconds. After rinsing and drying, a ceramic primer was applied and air-dried. Resin cement rods (n=24 per group) were built from a silicone mold. Specimens were stored in distilled water for 24 hours before microshear bond testing. Failure mode was observed under a digital microscope. Data were analyzed by using the Kruskal-Wallis and Mann-Whitney nonparametric tests (α=.05). RESULTS Intaglio staining negatively affected the microshear bond strength for both ceramics. A significant difference was observed between Gmax1 (3.5 ±1.73 MPa) and Gmax2 (3.7 ±2.1 MPa) when compared with Gmax0 (14.2 ±4.4 MPa) and also between GPress0 (25.7 ±5.1 MPa) and Gpress1 (1.8 ±2.7 MPa). No difference was observed between 1 and 2 stain layers for Gmax. Most failures were adhesive for Gmax0, mixed for Gpress, and cohesive within the stain layer for experimental groups. CONCLUSIONS Intaglio surface staining with a stain and glaze mixture caused a significant reduction in bond strength between resin cement and both ceramics tested.

Aim: Zirconia-based restoration is successfully replacing metal ceramic restorations in posterior areas. Although higher mechanical properties of zirconia, their use in compromised situation is questionable. Hence, there is a need to modify the design which to strengthen the framework. The aim of this in vitro study was to evaluate the influence of lingual collar design on the flexural strength of CAD/CAM-fabricated posterior three-unit zirconia framework. Materials and Methods: A mandibular metallic stainless steel master mold is designed for a three-unit fixed partial denture framework. All CAD-milled 20 samples are divided into two groups based on the design. Group A––with collar (10 samples) and Group B––without collar (10 samples), tested using universal testing machine to calculate the mean fracture load and flexural strength. Statistical Analysis Used: Descriptive statistics and independent sample t test were used to find the difference between the groups, and simple linear regression was used to find the relationship between load and displacement between the groups. Results: The result of the mean flexural strength for Group A was 11328.06 ± 3770MPa and for Group B was 7633.95 ± 3196 MPa; the mean fracture strength observed for Group A was 1274.04 ± 424 MPa and for Group B was 858.80 ± 359 MPa. A statistically significant difference was observed in flexural strength between Groups A and B (P < 0.05). Conclusion: Zirconia framework with connector dimension of 7 mm2 with lingual collar design can be successfully incorporated in compromised situation where an ideal connector dimension of 9 mm2 cannot be placed.

STATEMENT OF PROBLEM Studies investigating the mechanical stability of lithium disilicate-strengthened aluminosilicate glass ceramic that do not require sintering after milling compared with other computer-aided design and computer-aided manufacturing (CAD-CAM) materials are lacking. PURPOSE The purpose of this in vitro study was to investigate the flexural strength of CAD-CAM zirconia, lithium disilicate, and lithium disilicate-strengthened aluminosilicate glass ceramics with and without fatigue conditions. MATERIAL AND METHODS Specimens (N=90, n=15) (12×4×3 mm) from the following CAD-CAM materials were prepared and polished: lithium disilicate glass ceramic (IPS e.max CAD); lithium disilicate-strengthened aluminosilicate glass ceramic (N!ce); and zirconium dioxide ceramic (IPS e.max ZirCAD). All specimens were divided into 2 subgroups: immediate testing without aging and simulation of aging by using a mastication simulator for 1 200 000 cycles (5 °C-55 °C). Thereafter, flexural strength testing was performed by using a universal testing machine (1 mm/min) on nonaged and aged specimens. The data were evaluated by using nonparametric 2-way ANOVA and Wilcoxon rank post hoc tests (α=.05). RESULTS Both the material type and aging significantly affected the results (P<.001). The interaction was not significant (P>.05). Under nonaged conditions, zirconium dioxide ceramic (1136 ±162 MPa) showed significantly higher mean ±standard deviation flexural strength (P<.001) than lithium disilicate (304 ±34 MPa) and lithium disilicate-strengthened aluminosilicate glass ceramic (202 ±17 MPa). The glass ceramic groups were also significantly different from each other (P<.001). After aging, zirconium dioxide (1087.9 ±185.3 MPa) also presented significantly higher mean ±standard deviation flexural strength (P<.001) than lithium disilicate (259 ±62 MPa) and lithium disilicate-strengthened aluminosilicate glass ceramic (172 ±11 MPa) (P<.001). Aging significantly decreased the flexural strength of lithium disilicate (14.6%) (P=.03) and lithium disilicate-strengthened aluminosilicate glass ceramic (14.5%) (P=.01) but had minimal effect on the zirconium dioxide ceramic (4.3%) (P=.29). CONCLUSIONS Among the tested CAD-CAM materials, the mechanical performance of lithium disilicate-strengthened aluminosilicate glass ceramic was comparable with that of lithium disilicate and considerably lower than that of zirconia. Aging decreased the flexural strength of both lithium disilicate and lithium disilicate-strengthened aluminosilicate glass ceramic.

Background. Insufficient information exists regarding the fracture resistance and failure pattern of newly developed zirconia-reinforced lithium disilicate (ZL, Vita Ambria) onlays. This in vitro study compared the fracture resistance of two types of onlays: monolithic lithium disilicate (LD) and monolithic ZL. Methods. Forty-eight ceramic onlay restorations were fabricated on epoxy dies using a maxillary first premolar model. The samples were divided into two main groups: LD and ZL. Half of each group was subjected to thermomechanical fatigue loading (TML) using a chewing simulator. All the samples were cemented with self-adhesive resin cement. Subsequently, they were loaded until failure in a universal testing machine, and the fracture patterns and resistance were recorded. Results. Before TML, ZL demonstrated the highest statistically significant mean fracture resistance (499.76±34.14N) compared to LD (470.40±27.38N). After TML, ZL showed the highest non-statistically significant mean fracture resistance (429.27±131.42N), while LD’s mean fracture resistance decreased (377.31±62.18N). Conclusion. Monolithic zirconia-reinforced onlays demonstrated higher fracture resistance and a more favorable failure mode compared to LD. However, the impact of thermomechanical aging resulted in reduced fracture resistance for both materials, with a notable preference observed for ZL.

Conservative dentistry introduced modern restoration designs, contributing to the greater use of partial-coverage ceramic restorations. New strong bondable ceramic materials made fabricating partial coverage ceramic restorations easier to restore the badly destructed teeth. This study investigated the impact of three distinct overlay preparation designs on the marginal fit (both before and after thermal aging) and the fracture resistance of overlay restorations fabricated using advanced zirconia-reinforced lithium disilicate (ALD) CAD/CAM glass-ceramic blocks. Using a standardized preparation protocol, three typodont molars were prepared to receive three different indirect overlay ceramic restoration designs. The typodont teeth were duplicated to get 27 resin dies that were randomly allocated into three groups (n = 9) based on the preparation design; group (O): a traditional overlay preparation with anatomical occlusal reduction, group (OS): anatomical occlusal reduction with circumferential shoulder finish line, and group (OG): anatomical occlusal reduction with a central groove preparation at the mid-occlusal surface. After standardized restorations fabricated following the manufacturer’s guidelines, the restorations were cemented to their corresponding dies and exposed to thermal aging corresponding to 6-month clinical service. Marginal gap was measured before and after thermal aging procedure using an optical microscope. To measure fracture resistance, specimens were loaded till failure using the universal testing machine. The Kruskal Wallis test was utilized to assess data among the groups, followed by Dunn’s post hoc test with Bonferroni correction. Differences in the marginal fit before and after thermal aging were evaluated using Wilcoxon Sign Rank test. A statistically significant difference in marginal fit was observed between the studied groups, with a p-value of 0.032 where group OS has the lowest micro gap compared to group OG and group O. The fracture resistance group (O) recorded the highest fracture resistance with a statistically significant difference between the studied groups at p value = 0.043. Adjusting the tooth preparation significantly influenced both the fracture resistance load and the marginal fit observed for advanced zirconia-reinforced lithium disilicate glass-ceramic (ALD) overlays.

Background. An esthetically acceptable ceramic restoration should have optical properties like the teeth and reflect, transmit, and absorb light. The present investigation compared how hydrothermal aging affected the properties of two types of zirconia and lithium disilicate. Methods. Thirty rectangular samples (12×14×1 mm) were prepared and sectioned from three different ceramic blocks/blanks (n=10), then assigned into three groups according to the ceramic type: group Z: IPS e.max ZirCAD prime, gradient zirconia (3Y/5Y-TZP); group K: Katana UTML (5Y-TZP); and group E: IPS e.max CAD (lithium disilicate). Color analysis of samples was performed before and after hydrothermal aging (1, 3, and 5 hours) using a spectrophotometer. Color difference (∆E00), translucency parameter (TP00), and contrast ratio (CR) were evaluated. The microstructural analysis was performed using x-ray diffraction (XRD). Data were statistically analyzed at a significance level of P<0.05. Results. A statistically significant variation was observed across means of ∆E00, TP00, and CR at different times. Group Z displayed the highest statistically significant mean ∆E00. Group E demonstrated the greatest statistically significant mean TP00. Group K exhibited the most statistically significant mean CR. Conclusion. Hydrothermal aging significantly affected the optical characteristics of lithium disilicate and zirconia ceramics. The translucency of samples increased with aging.

  Introduction: Endocrown is an indirect restoration following the endodontic treatment made of ceramic material as a substitute for post core crown. The endocrown is cemented to the inner wall of the pulp chamber and to the cavity margins to increase the macromechanical retention. Material commonly used are monolithic zirconia and lithium disilicate; both can be obtained using the CAD/CAM technique. Good endocrown restoration must be able to handle the chewing workload especially on the posterior tooth. Objective: To determine the difference in fracture toughness of monolithic zirconia and lithium disilicate CAD/CAM endocrown. Methods: This study used 6 endocrown CAD/CAM samples, attached to typodont prototype in 3D resin printing model produced by the printing machine. Samples were divided into 2 groups. Group A were monolithic zirconia endocrowns and group B were lithium disilicate endocrowns. The fracture toughness was calculated using the Universal Testing Machine (UTM). Results: Fracture toughness of the monolithic zirconia endocrown were 2.747 N and lithium disilicate were 769 N. The unpaired t test showed that there was significant difference in fracture toughness between groups (p < 0,05). Conclusion: Monolithic zirconia endocrown has a higher fracture toughness compared to the lithium disilicate endocrown, but lithium disilicate is more recommended as an endocrown restoration material because its fracture toughness is closer to masticatory load of posterior teeth.

ABSTRACT Objectives This study investigates how titanium‐base (Ti‐base) abutment height, crown design, and force angulation affect biomechanics in an anterior single‐implant restoration, using finite element analysis. Material and Methods A three‐dimensional anterior maxilla model was constructed with linear elastic properties. Two Ti‐base heights (3.5, 5.5 mm) and two crown heights (8, 11 mm) were tested as monolithic zirconia or bilayer (zirconia core veneered with lithium disilicate). A 146 N load was applied at the cingulum at 45° or 65°. von Mises stress (VMS) was computed in the crown, abutment, and surrounding bone. Results A 3.5 mm Ti‐base with an 8 mm monolithic zirconia crown (SSZ) produced the lowest crown and abutment VMS. The highest crown VMS occurred in the 11 mm bilayer crown on a 5.5 mm Ti‐base (LLZEX) at 45°, while the highest abutment VMS occurred in the 3.5 mm Ti‐base with an 8 mm bilayer crown (SSZEX) at 65°. An increase in crown height raises crown stresses, whereas the impact of abutment height depends on configuration and angle. In bone, 45° loading increased VMS compared with 65° across all models. Conclusions In anterior single‐implant models, the lowest restoration stresses were achieved with a short crown on a 3.5‐mm Ti‐base and monolithic zirconia. Long crowns (11 mm) increased crown stresses, and abutment height should be tailored to material and anticipated loading direction rather than adjusted by a single rule. Oblique loading consistently raised bone stress compared with 65°, underscoring the need to optimize for axial force transmission.

PURPOSE Under thin, partial coverage restoration the proper cement thickness to be clinically employed still remains an issue. The aim of this study was to determine the failure and success rates of simplified lithium disilicate occlusal veneers as a function of cement thickness. The null hypothesis was that cement thickness has no effect on the fatigue resistance. METHODS Sound human molars were severed in a plane parallel to the occlusal surface to create a flat dentin surface surrounded by enamel edges. Forty-five occlusal veneers 1.0 mm thick (IPS e.max CAD LT) were luted to the teeth with Multilink Automix resin cement, creating 3 experimental groups (n=15) with cement thicknesses of 50, 100, and 200 µm. The restorations were fatigue-cycled using a ball mill machine containing zirconia and stainless steel spheres. Twelve 60 min cycles were performed. Survival statistics were applied to "failure" and "success" events, comparing the three groups using a log-rank Mantel-Cox test and a log-rank test for trends (alpha = 0.05). RESULTS The failure and success rates were not significantly influenced by cement thickness (P = 0.137 and P = 0.872, respectively); thus, the null hypothesis was accepted. However, when log-rank test for trends was applied to failure events, the tendency to have less failures with increasing thicknesses was found statistically significant (P = 0.047). CONCLUSIONS The cement thickness within the range adopted here did not have a significant effect on the failure or success rate of lithium disilicate occlusal veneers when exposed to randomized impact stresses generating fatigue phenomena.

Objectives  The current trial aimed to compare lithium disilicate (LS2) endocrowns' clinical performance, gingival health, and parental satisfaction to those of prefabricated zirconia crowns (ZCs) over a 24-month of follow-up. Materials and Methods  This study designed as a spilt-mouth randomized controlled trial. A total of 88 pulpotomized mandibular second primary molars of 44 children were assigned into two equal groups. Forty-four molars were restored with prefabricated primary ZCs (control group) and the same number were restored with LS2 endocrown (intervention group). Clinical performance and gingival status were evaluated using a modified United States Public Health Service criterion, and plaque and gingival indices. Parental satisfaction was assessed using a 5-point Likert-scale questionnaire. Statistical Analysis  Paired data were analyzed using McNemar's test, a statistical test used on paired nominal data, and paired t -tests. The significance level was set to 5% at 95% confidence interval. Results  Both restorations showed comparable gingival health status over the follow-ups. Marginal adaptation of the endocrowns and ZCs at the end of follow-up was 95.5 and 90.9%, respectively ( p  = 0.68). For marginal integrity and discoloration, both restorations showed similar results at the follow-ups. The overall parental satisfaction of both groups was statistically insignificant ( p  = 0.07). However, parents were more satisfied with the endocrown color over that of the ZC ( p  < 0.05). Conclusion  Endocrowns' clinical performance and gingival health were comparable to those of ZCs. For both restorations, parental satisfaction was nearly similar except for the color that showed an advantage in favor of the endocrowns.

STATEMENT OF PROBLEM The influence of ceramic type, cement shade, and ceramic thickness on the final color of the restoration and its masking ability is unclear. PURPOSE The purpose of this in vitro study was to investigate the effect of the ceramic type and translucency parameters, ceramic thickness, and cement shade on the color of the definitive restoration and its masking ability. MATERIAL AND METHODS A total of 120 ceramic specimens were fabricated in different thicknesses and divided into 10 groups: high translucency zirconia (HTZ 0.8, 1.2, 1.6 and 2 mm) (ZX2 98; Dental Direct), porcelain-fused-to-zirconia (PFZ1.5 and 2 mm) (DD Bio ZW iso color High Strength; Dental Direkt), monolithic low translucency lithium disilicate (LT 1 and 1.5 mm) (e.max; Ivoclar AG), bilayered glass-ceramic with a high opaque lithium disilicate (HO 1.5 and 2 mm) (e.max; Ivoclar AG). The color and translucency of the specimens were measured based on the L*a*b values and remeasured after applying resin cement evaluation pastes (Panavia V5 Try in paste; Kuraray Dental) in 3 colors: A2, opaque (O), or white (W) over 2 background materials (nickel chromium alloy or composite resin shade A2). The VITA Classic shade guide was used as the reference L*a*b value to evaluate the color matching capability of different ceramic-cement combinations. Color change (ΔEab) was measured, and the perceptibility threshold (PT) was set at 2.6 and the acceptability threshold (AT) at 5.5. RESULTS The mean ΔE of the specimens ranged from 0.4 to 4.5. The type of ceramic significantly affected the color and translucency parameter (P<.001). In all groups, translucency decreased significantly with the increasing thickness of the ceramic (P<.001). According to the perceptibility threshold, the color of the nickel chromium background could be concealed by all 2 shades of cement (A2, opaque, and white). Nevertheless, the LT 1-mm, LT 1.5-mm, HTZ 0.8-mm, and HTZ 1.2-mm groups exhibited noticeable color changes when opaque cement was applied. Specimens with lower translucency parameters had better color matching with the A2 color. The HTZ 0.8-mm A2, LT 1-mm A2, and HTZ 0.8-mm W groups showed the least color match, with mean ΔE values of 12.4, 11.9, and 11.3, respectively. However, the PFZ 2-mm O and PFZ 2-mm W groups exhibited the best color match, with mean ΔE values of 1 and 1.4. CONCLUSIONS The thickness of the ceramic had a significant effect on its translucency. Moreover, the translucency of the ceramic influenced its masking ability and had a direct correlation with the color change in the presence of cement. Ceramic materials with an opaque framework had lower translucency but better color matching with the reference shade.

The purpose of this study was to investigate the wear behavior of pure titanium when opposed to six different crown restorative materials. Abrader specimens were prepared by casting pure titanium and these were paired with substrates including pure titanium, resin composite, lithium disilicate, zirconia, silver-palladium-copper (Ag-Pd-Cu) alloy, and bovine enamel. The wear volume of each abrader and substrate specimen was measured using the two-body wear test, and factors affecting wear behavior, such as microstructures and hardness, were evaluated. Results indicated that titanium-to-titanium abrasion caused significant wear in both the abrader and the substrate. In contrast, no significant wear was observed for the zirconia and Ag-Pd-Cu alloy against titanium. SEM images showed linear wear marks in most specimens other than zirconia and resin composite, microcracks in enamel, and filler fall in resin composite. A strong correlation between the wear volume and Vickers hardness was found for ceramics, resin composites, and enamel. However, due to the small slope of the approximate straight line in this correlation suggests that the wear behavior of materials when abraded by titanium is only partially influenced by the microstructure and hardness of the material.

STATEMENT OF PROBLEM How different restorative materials designed for computer-aided design and computer-aided manufacturing (CAD-CAM) and substance loss affect the fracture resistance of endodontically treated maxillary first premolars restored with 1-piece endodontic crowns is unclear. PURPOSE The purpose of this in vitro study was to assess the impact of various CAD-CAM restorative materials and residual tooth structure on the fracture resistance of endodontically treated maxillary first premolars restored with 1-piece endodontic crowns. MATERIAL AND METHODS Sixty-four maxillary first premolars were endodontically treated and divided into 4 main groups (n=16) according to the restorative material: ZP: Zirconia 1-piece endodontic crowns group (IPS e.max ZirCAD Prime; Ivoclar AG); RM: Resin-modified 1-piece endodontic ceramic crowns group (Katana Avencia; Kuraray Noritake Dental Inc); LD: Lithium disilicate 1-piece endodontic crowns group (IPS e.max CAD; Ivoclar AG); and CG: A control group restored with zirconia posts, composite resin cores, and lithium disilicate crowns (IPS e.max CAD; Ivoclar AG). Teeth in subgroups had either 1 or 2 residual coronal walls (n=8). All specimens underwent dynamic loading for 1 200 000 loading cycles in a masticatory simulator. A universal testing machine was then used to quasi-statically load the specimens at 30 degrees until fracture. For the statistical test, the Generalized Linear Model (GLM) with a gamma distribution and log link function was chosen (α=.05). RESULTS None of the specimens showed any signs of debonding or fracture during the fatigue test. Mean ±standard deviation fracture loads ranged from 247.6 ±70.2 N (for group RM1) to 1211.5 ±243.2 N (for group RM2). A statistically significant increase in fracture resistance was observed with the increasing number of walls (P<.001). However, different CAD-CAM restorative materials did not affect the fracture resistance of endodontically treated maxillary first premolars restored with 1-piece endodontic crowns (P<.05). CONCLUSIONS In this in vitro study, increasing the number of remaining walls dramatically enhanced the fracture resistance of endodontically treated maxillary first premolars restored with 1-piece endodontic crowns and subjected to thermomechanical fatigue, irrespective of the type of restorative material used.

Root canal treatment (RCT) often results in significant loss of tooth structure, increasing the risk of tooth fracture under occlusal forces. This study aimed to evaluate the impact of different restoration timings on the fracture resistance of teeth after RCT and to compare the effectiveness of 3 restoration methods: full crown, onlay, and occlusal veneer. Sixty extracted human molars underwent standardized RCT and were randomly assigned to 9 groups (n = 6–7) in a 3 × 3 factorial design: immediate (1 week), early (2–3 weeks) or delayed (4–6 weeks) restoration, each receiving either a zirconia full crown, lithium-disilicate onlay or composite occlusal veneer. After thermomechanical aging (5000 thermal cycles, 50000 chewing cycles, 50 N), specimens were loaded to fracture (1 mm min−1). Mean fracture loads declined with delayed restoration: immediate 2 356 ± 413 N, early 2 086 ± 389 N, delayed 1 754 ± 357 N (P < .001). Full crowns resisted highest loads, followed by onlays and veneers (P < .01); timing × method interaction was significant (P = .038). Immediate restoration yielded 85% repairable failures; delay increased non-repairable root fractures to 55% (P = .004). Earlier restoration after RCT significantly enhances fracture resistance and clinical prognosis. While full crown restoration offers superior protection, onlay and occlusal veneer are viable alternatives that balance fracture resistance and tooth structure preservation.

Failure to restore missing teeth in time can easily lead to the mesial tilting of the distal abutment teeth. However, a fixed partial denture (FPD) can improve stress conduction and distribution and prevent periodontal injuries. In these more complex cases, it is necessary to consider various factors comprehensively to improve conventional treatment planning and achieve better results. We selected a patient with a missing first molar and a mesial inclination of the second molar, leaving inadequate space or bone mass for implant denture restoration, necessitating an FPD for restoration. Three-dimensional finite element analysis (3D-FEA) combined with photoelastic analysis were used to explore how the inclination angle (0 ‒ 30°) and different dental restoration materials (zirconia, lithium disilicate, polymer-infiltrated ceramic network, and resin composite) affect the biomechanical behaviour of FPD‒abutments‒periodontal tissue complex. The stress was easily concentrated in the FPD connectors, enamel shoulder collar, periapical area, and root bifurcation. The stress on FPD and the periodontal ligament (PDL) of the second premolar increased with an increase in the elastic modulus of FPD, with an opposite trend in the abutments, the alveolar bone, and the PDL of the second molar. The stress on the FPD and alveolar bone increased with increased inclination angle of the distal abutment. The stress on two abutments and their PDL were positively correlated with the inclination angle in two stages; however, when the inclination angle > 12°, the second premolar and its PDL showed a negative correlation. FPDs can be used for restoration within 24° of distal abutment inclination, but protecting the abutments (< 12° especially) and the periodontal tissue (> 12° especially) must be taken seriously. For this purpose, an FPD material with higher strength is recommended.

OBJECTIVES To evaluate the effects of background color, ceramic type and coping thickness on masking ability (ΔE) and translucency parameter (TP) of CAD/CAM lithium disilicate glass-ceramic/monolithic zirconia and, to determine the correlations between coping thickness, TP and ΔE. METHODS A total of 120 ceramic specimens (2 mm, 1 mm and 0.5 mm thickness; n = 10) of four CAD/CAM ceramics: IPS e.max, IPS ZirCAD, Upcera Li CAD and Upcera TT CAD, were studied. Specimens were tested over nine fabricated backgrounds: A1, A2, A3.5, ND2 and ND7 shade resin-based composites, cobalt-chromium alloy (CC), medium precious alloy (MPA), black (B) and white (W). CIELab values (L*, a* and b*), color difference (ΔE) and translucency parameter (TP) were measured and calculated using a digital spectrophotometer (color i7, X-Rite, Pantone®). Data were analyzed using the Shapiro-Wilk test, one-way ANOVA, three-way ANOVA, independent t-tests and Tukey post-hoc tests (p < 0.05). RESULTS 2 mm CAD/CAM ceramics showed ideal color matching (ΔE<2.6) over different backgrounds, except for CC, B and W backgrounds. Monolithic zirconia had lower ΔE values than lithium disilicate glass-ceramics. ΔE and TP values significantly reduced with the increased coping thickness (p < 0.05). Regardless of ceramic type and thickness, a strong TP-SD of ΔE correlation was observed. SIGNIFICANCE CAD/CAM ceramic restoration color was significantly affected by background color, ceramic type and coping thickness. TP is a promising predictor for appropriate ceramic selection to receive an acceptable CAD/CAM ceramic restoration aesthetic.

This in vitro study evaluated the influence of restoration design (bi-layered vs. monolithic) and manufacturing technique on the marginal discrepancy and internal fit of 3-unit zirconia fixed dental prostheses (FDPs). Mandibular second premolars and second molars were prepared as abutments in a 3-unit zirconia bridge to develop four groups (n = 10 FDPs): MZ: Monolithic zirconia FDPs, ZL: zirconia framework veneered by the hand-layering technique, ZP: zirconia framework veneered by the heat-pressed technique, and CAD-on: zirconia framework veneered by CAD/CAM lithium-disilicate glass–ceramic. All the zirconia FDPs were cemented to their corresponding die replicas using dual-cure resin cement and were subjected to compressive cyclic loading at a load range for half a million cycles using a universal testing machine. FDPs were sectioned mesiodistally to measure the marginal gap and internal fit using scanning electron microscopy. The measurements were taken at pre-assigned points of each abutment. Data were statistically analyzed via a Kruskal–Wallis test (α = 0.05). No significant differences were found between the monolithic and bi-layered zirconia groups in terms of the marginal discrepancy. However, there was a significant difference in the marginal gap between the zirconia groups. The marginal gap between monolithic and bi-layered zirconia FDPs was within the clinically acceptable range (<100 μm). Comparable mean values of the marginal gaps of 3-unit monolithic and veneered zirconia FDPs were found. Therefore, the FDP design and veneering methods did not affect the marginal discrepancy. However, the mean internal gap varied among the experimental groups. As the current in vitro investigation demonstrated equivalent mean values of marginal gaps of both 3-unit monolithic and bi-layered zirconia FPDs, the use of monolithic 3-unit zirconia FPDs would be a viable alternative fabrication technique.

PURPOSE To evaluate the effect of restoration design on fracture resistance and stress distribution of veneered and monolithic 3-unit zirconia fixed partial dentures (FDPs) using finite element analysis (FEA). MATERIALS AND METHODS Identical epoxy resin replicas of mandibular second premolar and second molar (to serve as abutment for the 3-unit bridge) were divided into four groups (n = 10): monolithic zirconia (MZ) restorations; conventional layering veneering technique (ZL), heat-pressed technique (ZP), or CAD/CAM lithium disilicate glass ceramic (CAD-on). Specimens were subjected to compressive cyclic loading on the mesio-buccal cusp of the pontic (load range 50 to 600 N; aqueous environment; 500,000 cycles) in a universal testing machine. Data were statistically analyzed at 5% significance level with Fisher exact test and Kaplan-Meier survival analysis. 3D models were constructed in accordance with experimental groups. The stress distribution in each model was analyzed and evaluated according to the location and magnitude of the maximum principal stresses (MPS) using ANSYS software. RESULTS Specimens from ZL and ZP groups failed at different stages of the 500,000 cycles fatigue, while CAD-on and MZ restorations survived fatigue test. Statistically, there was a significant difference between the groups (P < .001). The MPS were located under the mesial connector in both monolithic and bilayered 3-unit zirconia FDPs. These stresses were found to be higher in monolithic geometries compared to bilayered zirconia FDPs. CONCLUSION Monolithic 3-unit zirconia and CAD-on zirconia frameworks resulted in superior fracture resistance. Restoration design significantly affected the stress distribution of 3-unit zirconia FDPs.

Abstract This study aimed to evaluate the influence of material and crown design on the biomechanical behavior of implant-supported crowns with hybrid abutment (HA) through three-dimensional (3D) finite element analysis. The study factors were the type of material used as the mesostructure or crown (zirconia, lithium disilicate, and hybrid ceramic) and the crown design cemented to the titanium base (mesostructure cemented to the titanium base and a crown cemented on it (HaC); hybrid crown-abutment, the abutment and crown are manufactured as a single piece and cemented to the titanium base (HC); monolithic crown cemented on the titanium base and screwed to the implant (CS); and monolithic crown cemented on the titanium base (CC). Four 3D models were constructed using an implant with an internal connection, and an oblique load of 130 N was applied at 45° to the long axis of the implant. The models were evaluated using the von Mises stress for crown, abutment, screw, and implant and maximum principal stress for bone tissues. The lowest stresses occurred in the groups with a lower elastic modulus material, mainly hybrid ceramics, considered a material with greater resilience. The cemented crown group presented the lowest stress values. The stresses were concentrated in the cervical region of the crown at the titanium crown/base interface. Mesostructures made of materials with a higher elastic modulus exhibited a higher concentration of stress. The presence of a screw hole increased the stress concentration in the ceramic crown. Cemented ceramic crowns exhibited better biomechanical behavior than screw-retained crowns.

Aim: The objectives of this article was to determine the minimum thickness of two monolithic materials for a posterior implant prosthesis. Materials and methods sixty monolithic IPS E.MAX CAD and zirconia crowns with different occlusa l thicknesses were made with the use of a computer-aided design/computer-aided manufacturing technique was divided into 3 experimental groups: group (1) 0.5 mm group (2) 0.7mm group (3)1mm. A universal testing machine was used to determine the fracture load value. The restoration was loaded until fracture; the fracture resistance was registered. Two-way ANOVA has been used to examine the data., followed by the least significant difference LSD test. One-way ANOVA variance analysis was used to examine the differences in fracture load of monolithic zirconia or IPS E.MAX CAD at various thicknesses (p=0.05). Results vertical load test revealed that the fracture resistance of monolithic zirconia higher than the lithium disilicate crown (E.MAX CAD). The results showed that the highest mean value of fracture load test was obtained in the ice zirconia translucent with 1mm thickness group (1880N), while the lowest mean value was in the E.MAX CAD with thickness 0.5mm Group (223N). Conclusions: The fracture resistance of CAD-CAM monolithic crowns is influenced by the occlusal thickness. zirconia prosthesis with occlusal thickness 0.7mm,1mm had a high fracture resistance when compared with E.MAX CAD.

This study evaluated the influence of distinct substrates on the mechanical fatigue behavior of adhesively cemented simplified restorations made of glass, polycrystalline or polymer infiltrated-ceramics. CAD/CAM ceramic blocks (feldspathic - FEL; lithium disilicate - LD; yttria-stabilized zirconia - YZ; and polymer-infiltrated ceramic network - PICN) were shaped into discs (n = 15, Ø = 10 mm; thickness = 1.0 mm), mimicking a simplified monolithic restoration. After, they were adhesively cemented onto different foundation substrates (epoxy resin - ER; or Ni-Cr metal alloy - MA) of the same shape (Ø = 10 mm; thickness = 2.0 mm). The assemblies were subjected to fatigue testing using a step-stress approach (200N-2800 N; step-size of 200 N; 10,000 cycles per step; 20 Hz) upon the occurrence of a radial crack or fracture. The data was submitted to two-way ANOVA (α = 0.05) to analyze differences considering 'ceramic material' and 'type of substrate' as factors. In addition, a survival analysis (Kaplan Meier with Mantel-Cox log-rank post-hoc tests; α = 0.05) was conducted to obtain the survival probability during the steps in the fatigue test. Fractographic and finite element (FEA) analyzes were also conducted. The factors 'ceramic material', 'type of substrate' and the interaction between both were verified to be statistically significant (p < .001). All evaluated ceramics presented higher fatigue failure load (FFL), cycles for failure (CFF) and survival probabilities when cemented to the metallic alloy substrate. Among the restorative materials, YZ and LD restorations presented the best fatigue behavior when adhesively cemented onto the metallic alloy substrate, while FEL obtained the lowest FFL and CFF for both substrates. The LD, PICN and YZ restorations showed similar fatigue performance considering the epoxy resin substrate. A more rigid foundation substrate improves the fatigue performance of adhesively cemented glass, polycrystalline and polymer infiltrated-ceramic simplified restorations.

No abstract available

No abstract available

BACKGROUND Various ceramic materials have been used for esthetic rehabilitation with implants, but the issues regarding the dissipation of masticatory loads are not well understood. OBJECTIVES This in vitro quasi-static study aimed to evaluate with the photoelasticity test the dissipation of stress around dental implants with regard to different rehabilitation materials. MATERIAL AND METHODS A photoelastic model was elaborated in resin, where a conical Morse-tapered implant was inserted. On the abutments (1 per crown), 6 single crowns were prepared using different materials to form 6 groups: feldspathic ceramic (G1); chrome-cobalt alloy covered with ceramic (G2); hybrid ceramic (G3); zirconia covered with ceramic (G4); zirconia (G5); and lithium disilicate (G6). Axial loads of 100 N (load 1) and 300 N (load 2) were applied in the center of the crowns, and photoelastic images were captured and analyzed. The total area of stress dissipation was measured for each group. Then, a computational program was developed to measure the number of pixels of the colors generated in each group. Two image sizes were analyzed - total image and crestal image. RESULTS Counting the numbers of pixels of the colors in the total images showed that G6 > G4 > G5 > G1 > G2 > G3 when load 1 was applied. When load 2 was applied, the sequence was G6 > G4 > G1 > G3 > G2 > G5. In the evaluation of the crestal area, the obtained results were G4 > G5 > G1 > G3 > G2 > G6 with load 1 and G5 > G1 > G2 > G6 > G4 > G3 with load 2. CONCLUSIONS Within the limitations of this in vitro quasi-static study, the findings indicate that the zirconia crown (G5) presented higher stress in the crestal images, while the lithium disilicate crown (G6) presented higher stress in the total images.

To assess the impact of resin cement color and the thickness of monolithic CAD/CAM materials on the final color of the fixed dental restoration. Four high translucent monolithic CAD-CAM materials in shade A2, including lithium disilicate glass-ceramic (IPS e.max CAD, IP), monolithic zirconia (Ceramill Zolid HT+, CZ), two zirconia-reinforced lithium silicate ceramics (VITA Suprinity, VS, and Celtra Duo, CD) were prepared as rectangular specimens measuring 12 × 14 mm in two thicknesses (0.5 mm and 1 mm), (N = 160, n = 20 per group). Subsequently, three different colors of PANAVIA™ SA(PV) Cement Universal Automix Universal (A2), White (W), and Translucent (Tr) polymerized resin cement specimens (12 × 14 × 0.2 mm) were placed underneath the ceramic samples. After and befor aging color values were measured. The color difference was calculated using CIEDE2000 formulae. Statistical analysis was conducted using a three-way ANOVA and EMF function with Bonferroni correction. The 3-way ANOVA for the color difference data showed a statistically significant effect of all three main factors ceramic thickness, materials, and resin cement (p < 0.05). Among these, resin cement color had the most pronounced influence on color change (ηp² = 0.974). The most significant color change was observed with a thickness of 0.5 mm and white cement, with mean ∆E values ranging from 7.72 to 3.40. All ceramic groups, except for monolithic zirconia, exhibited color changes exceeding the clinically acceptable threshold (∆E ≤ 3.5). Additionally, all ceramic groups, except for monolithic zirconia, were affected by thickness. The study revealed that material type and cement group significantly influenced ∆E values in certain ceramics (CD, IP), while others (CZ+, VS) remained unaffected at 1 mm thickness. These findings highlight the importance of selecting appropriate cement color and type to optimize the final esthetics of monolithic restorations.

Aim: In this study, it was conducted to examine the effect of the stress distribution of different restorative materials on the crown, abutment, implant and bone on the biomechanical behavior and safety factor of the materials. Material and Methods: Zirconia, lithium disilicate, and zirconia-reinforced lithium silicate ceramics were designed on a single implant-supported crown that replaced the missing lower first molar. The stresses of the components of the models and the safety factors of the crown materials were calculated after 400 N occlusal loading. Results: The zirconia model caused the lowest stress on the implant but the highest stress on the crown. When the elastic modulus of the material increased, the stress on the crown increased, but the stress transmitted to the implant decreased. However, despite this high stress in the crown, the highest safety factor was in zirconia. Conclusion: The safety factor of the restoration material depends on the flexural strength rather than the stress on the crown. The greater the flexural strength, the greater the safety factor, and for a long-surviving implant-supported restoration, it is important that the crown material has a high safety factor and low stress on the implant.

Because of the evolvement of digitalized dentistry and the need of a restoration that is fixed, there has been an introduction of many materials related to 3D printing in today’s market. The purpose of this study is to evaluate the resistance of fractures by comparing materials of ceramic which are of four kinds and they are zirconia-reinforced lithium disilicate, also Emax cad, and IPSS emax as well as 3Dprinting nanoceramic. Methods: 24 crowns were prepared (6sample for each type of the material) used in the study. And undergone artificial ageing before testing using the universal testing machine. Submission of results in SPSS for tests like Kruskal-Wallis as well as nonparametric test proved the difference in each material of ceramics and it differed at p ≤ 0.05 whereas in the methods used there is no such difference. The material which showed a resistance for fractures with a high value was the samples of ZLS which was about 1473.1 and the material which showed a resistance for fractures with a low value was the Emax cad and it was about 1013.7. To conclude, Value of Fracture resistance can have an impact because of the kind of material whereas there is no significant impact because of the preparation method.

STATEMENT OF PROBLEM The tooth in the esthetic zone can be restored using various direct and indirect restorative materials. While their appearance may be acceptable on the day of delivery, their optical characteristics may change over time, resulting in patient dissatisfaction and the need for replacement. A lack of clinical follow-up monitoring of the color stability of these restorations necessitates the development of methods that may offer insight into raising awareness of this issue. OBJECTIVE To assess the color stability of direct and indirect restorative materials following simultaneous aging in coffee and simulated toothbrushing followed by repolishing of the restoration. METHODS AND MATERIALS A central incisor ivory tooth was prepared for a veneer and was restored with seven different restorative materials (n = 5). A direct packable composite resin (PC), flowable composite resin (FC), and 5 indirect restorative materials (lithium disilicate [LD], 4% yttria partially stabilized zirconia [4Y-PSZ], zirconia reinforced lithium silicate [LS], additive manufactured nanoceramic [AM], and milled composite resin [MC]). The indirect veneers were cemented with a light-cured adhesive resin cement. All veneers were polished according to manufacturers' instructions. The aging method was defined by immersion in coffee at 37°C for 24 h and then moving to the toothbrush simulator for a 3500-brush cycle, and this cycle was repeated for a total of 28 days between immersion in coffee for a total of 14 days and a total of 50,000 toothbrushing cycles. After this period, the restorations were repolished according to the common clinically recommended method for each material. Spectrophotometric readings and standardized photographs were taken at baseline and following the 14-day aging method. Color difference (ΔEoo) was calculated for each veneer. A repeated measures two-way analysis of variance (ANOVA) and Tukey's post hoc test (α = 0.05) were used to analyze the data. RESULTS Both restorative material type and aging method affected ΔEoo (p < 0.001). Discoloration varied among restorative materials across aging method stages (p < 0.001). AM exhibited the greatest color difference after the aging method (9.1 ± 0.87), while ΔEoo values decreased following repolishing for all materials. Repolished 4Y-PSZ veneers demonstrated the lowest ΔEoo values (0.70 ± 0.53). CONCLUSIONS LD veneers maintained the highest degree of color stability during the method of aging. The restorative materials' original color may be restored to a level that is acceptable through repolishing. Not only did AM veneers exhibit a lack of color stability, but there was also visual staining of the margins. CLINICAL RELEVANCE A clinician's understanding of the composition of restorative materials and its impact on color stability and appearance over time determines their ability to select the most appropriate restorative material that can support esthetic longevity.

This study evaluated the clinical outcomes of a customized technique for restoring large-diameter root canals using prefabricated glass fiber posts (GFPs). The approach involved strategic modifications to accommodate increased root diameters and improve restoration longevity. A total of 104 crowns [45 e.max lithium disilicate (LidiSi) monolithic, 17 e.max LidiSi layered, 27 zirconia monolithic, and 15 zirconia layered] were cemented on endodontically treated teeth (ETT) with GFPs adapted using this technique. The restorations demonstrated a 97.1% survival rate over 24 months, confirming the method’s effectiveness, minimal invasiveness, and suitability for rehabilitating ETT. The high success rate underscores the durability of this personalized restoration approach. While these findings suggest promising long-term potential, further research is needed to fully assess the biomechanical impact of all involved components.

Background This retrospective observational clinical study designed to assess the clinical performance and outcomes of cemented one-piece molar endocrowns (ECs) using the United States Public Health Service (USPHS) criteria at various time intervals. Additionally, patient satisfaction for cemented ECs was measured using the Visual Analog Scale (VAS). Methods Clinical data were collected from 29 participants (mean age 26.34 ± 6.99 years) who received ECs at a specialist dental center. Twenty-four ECs were constructed from lithium disilicate glass-ceramic (LDGC) and five from multilayered zirconia. All patients were analyzed at each follow-up (baseline, 6, 12, 24, and 36 months). Clinical performance was evaluated using modified USPHS criteria, and patient satisfaction was measured with a VAS. Statistical analyses included ANOVA and McNemar tests, with significance set at p ≤ 0.05. Results After 36 months most LDGC restorations retained “Alpha” (clinically excellent) scores for marginal adaptation, color match, anatomical form, restoration integrity and retention; zirconia restorations showed a mix of Alpha and Bravo scores. Significant differences between the materials were found for color at baseline (p=0.001) and at 36 months (p=0.018) and for retention at 36 months (p=0.001). Overall patient satisfaction by VAS remained high across groups. Conclusion Despite the limitations of a small zirconia sample, LDGC ECs showed better color matching and retention than zirconia. Zirconia is still a viable option where strength is essential. Material selection should consider esthetic demands and occlusal load. Long-term studies with larger cohorts are needed for validation.

To explore the influence of different inlay materials, depth, and width variations on stress distribution using the finite element method, and to provide a quantitative theoretical basis for the selection of clinical inlay restoration schemes. A three-dimensional finite element model of the mandibular first molar was established. The models were organized into four main groups based on the restorative material: Zirconia, Lithium Disilicate (LD), Gold Alloy (GA), and Resin-Based Ceramics (RBCs). Each material group was further divided into nine subgroups, simulating MOD inlay restorations with different preparation parameters: inlay depth (d = 2 mm, 4 mm, or 6 mm) and width (w = 2 mm, 4 mm, or 6 mm). A total of 36 groups of models were constructed. A vertical and oblique static load of 100 N was applied to the occlusal surface, and the distribution characteristics of the maximum principal stress (MPS) under different variable combinations were analyzed. The MPS of the four types of inlays were all concentrated on the stress-bearing contact surface and the bottom of the inlays. In terms of materials, under vertical loading, when d = 2 mm and w = 2 mm, the Zirconia group had the highest MPS (143.2 MPa), the RBCs group had the lowest (115.5 MPa), and the values of the LD group (127.9 MPa) and the GA group (128.3 MPa) were between the two. According to this finite element study, the stress distribution is influenced by the complex interaction between the material properties and the geometry of the preparation. Moreover, the stress distribution of RBCs is more uniform than that of high-modulus materials. In clinical applications, the restorative materials and preparation parameters should be comprehensively selected according to the conditions of the affected teeth, and the long-term effects still need in-depth research.

Background Cigarette smoking is the most common form of tobacco use worldwide. With the frequent introduction of new dental materials, the effect of smoking on their optical properties such as long term color stability, should to be thoroughly investigated. Objective This in-vitro study aims to investigate the effect of smoking on the optical properties of contemporary dental ceramics used currently for restoration of teeth. Methods Five different materials in two shades (B1 and C1) were used with 15 samples from each pressable lithium disilicate (Emax), layered lithium disilicate (Lmax), porcelain fused to metal (PFM), monolithic zirconia (MZr) and layered zirconia (LZr) were used (n = 75). The samples were exposed to conventional cigarette smoke and color stability was assessed at four different time intervals i.e., baseline, 1 week, 1 month and 6 months. CIELAB color space (CIE L*a*b*) values were used to evaluate the color difference (ΔE). A one-way analysis of variance (Anova) was used for statistical analysis of ΔE. Significant P-value was kept as <0.05, followed by Tukey post-hoc test. Results All test materials demonstrated significant color differences (ΔE) after exposure to cigarette smoke (p < 0.05). For shade B1, the highest change in shade ΔE 17.02 was exhibited by Lmax, whereas the least change in shade was exhibited by Emax followed by PFM at values of ΔE 10.11 and 11.2 respectively. For shade C1, the highest change (11.47) in shade at 6 months was demonstrated by MZr, whereas lowest values of ΔE were exhibited by Emax (7.52). Conclusions Traditional smoking causes significant change in shade of dental ceramics which can affect the esthetics of the patients. All material samples tested showed the values of ΔE > 3.3 which is higher than the acceptable range. Lowest color change was observed in Emax and PFM.

BACKGROUND Rehabilitation of endodontically treated teeth with large coronal destruction is still a clinical challenge. No established guidelines specify where a conventional crown with fiber-reinforced composite (FRC) post-and-resin core or an endocrown (EC) is indicated and which material or pulpal extension should be used. OBJECTIVE To provide evidence for restoring severely damaged maxillary first molar (MFM) by comparing the fracture and debonding resistance after being restored with the ceramic EC and the conventional zirconia crown and FRC post-and-resin core. METHOD Models of a MFM with a mesial-occlusal-distal-palatal defect with different restoration strategies were created: C-FRC -- conventional crown with FRC post, EC-Zr-3/4/5 - zirconia EC with 3-/4-/5-mm pulpal extension, EC-Li-3/4/5 - lithium disilicate EC with 3-/4-/5-mm pulpal extension. Two loading conditions were applied: vertical loading - a 400-N force along the tooth's long axis; lateral loading - a 225-N force at a 45-degree angle buccally to the tooth's long axis. Three-dimensional finite element analysis and Weibull analysis were conducted for the above seven models. RESULTS The C-FRC group obtained the lowest maximal Mohr-Coulomb stress ratio (MσMC ratio) in the residual tooth structure under both loadings (0.2646 and 0.2815, respectively). The lowest MσMC ratio in the cement was in the EC-Li-5 group under both loadings (0.07660 and 0.3177, respectively). The lowest maximal shear stress at the adhesive interface was in the EC-Li-3 group under both loadings (5.700 MPa and 20.48 MPa, respectively). CONCLUSIONS The conventional crown with FRC post-and-resin core is still suitable for restoring a MFM with a mesial-occlusal-distal-palatal defect. Lithium disilicate EC with 3-mm pulpal extension may be a choice for the MFM where conventional restoration is not applicable.

INTRODUCTION: Endocrown restorations offer a promising alternative to restore endodontically treated teeth. However, various materials are available without being thoroughly evaluated. Purpose: The purpose of the study is to evaluate marginal fit and fracture resistance of endocrown restorations using three CAD-CAM materials. MATERIALS AND METHODS: Eighteen extracted permanent mandibular molars were selected to receive endocrown restoration. Teeth were randomly allocated into three groups based on material type (n=6). (LD): Lithium Disilicate, (FCZ): full contour zirconia, (RNC): resin nanoceramic. All Endocrown restorations were fabricated utilizing CAD-CAM technology. Restorations were adhesively luted to the corresponding prepared teeth and subjected to thermomechanical cycling corresponding to six months of clinical service. Marginal gap was measured before cementation and after cementation and aging using optical microscope. For measuring fracture resistance, samples were loaded till fracture occurs by using Universal Testing Machine. Optical microscope was used to evaluate mode of failure. One-way ANOVA and Tukey's post hoc test were used to analyze fracture resistance, while Two-way ANOVA and Tukey's post hoc test were used to analyze marginal gap. RESULTS: FCZ had the highest fracture load compared to RNC and LD. Zirconia recorded largest microgaps before cementation. CONCLUSION: FCZ showed the highest fracture resistance values. LD and RNC ceramics showed fracture resistance with comparable values recommending their use as endocrown restorations. The tested groups showed marginal fit results within the bounds of clinically acceptable parameters. The material type and artificial aging process had a significant impact on the marginal gap.

Background Monolithic zirconia is increasingly used in dental restorations for its high strength and biocompatibility. However, the impact of surface treatments—glazing, polishing, and air abrasion—on its flexural strength remains unclear due to inconsistent findings in existing studies. Methods Thirty zirconia specimens (25 × 6 × 3 mm) were milled from SuperfectZir disks using CAD-CAM technology and sintered at 1,350°C–1,500°C. Specimens were randomly assigned to three groups (n = 10). Group A was glazed at 790°C, Group B was subjected to grinding and polishing using diamond burs and ceramic kits, and Group C underwent airborne-particle abrasion with 110 µm alumina at 400 kPa. Flexural strength was tested using a universal testing machine via the three-point bending method. Results Group B (Grinding and Polishing) showed the highest mean flexural strength (748.70 ± 79.95 MPa), followed by Group C (Air Abrasion) (689.90 ± 76.95 MPa), and Group A (glazing) (553.30 ± 131.75 MPa). Mann–Whitney U tests showed significant differences between Group A and Groups B (p = .002) and C (p = .041), but not between Groups B and C (p > .05). Conclusion Surface treatments significantly influence the flexural strength of monolithic zirconia. Polishing most effectively enhances strength by reducing flaws. Glazing reduced strength, likely due to thermal stress, while air abrasion showed moderate improvement. Clinical choice should balance strength and aesthetics.

Introduction The main reason veneered zirconia restorations fail is due to porcelain veneer chipping. This chipping usually starts from wear marks on the chewing surface. As a result, small cracks under the contact area can grow into larger ones across the veneer layer. The veneer ceramic layer is more vulnerable to fractures because it has lower toughness and slightly lower stiffness compared to the base framework material. Thus, even when there's significant chipping, the main framework material usually stays protected with a thin layer of veneer ceramic on top. The aim of this in vitro study is to compare the edge strength of Monolithic Zirconia Crowns with that of Indirect Composite Layered Zirconia Crowns without aging. Materials and methods This research involved creating 12 hand-layered all-ceramic crowns and 12 indirect composite layered zirconia crowns. The sample size was determined using a G*Power calculation (Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany). The zirconia frameworks (Upcera HT White; UPCERA Dental America Inc., Cerritos, CA, US) were milled and sintered following the manufacturer's instructions. For the all-ceramic group, veneering porcelain (e.max Ceram; Ivoclar Vivadent, Schaan, Liechtenstein) was hand-applied. In contrast, the indirect composite group utilized Ceramage (Shofu, Kyoto, Japan). An Instron 4501 universal testing machine (Instron Corp., Canton, MA, USA) was employed for the edge chipping tests, and a Vickers indenter (Shanghai Toyo Diamond Tools Co., LTD, Shanghai, China) was used to apply the load. The mean value for edge chipping was analyzed using an unpaired t-test with IBM SPSS Statistics for Windows, Version 26 (Released 2019; IBM Corp., Armonk, NY, USA). The normality of the data was confirmed, and statistical significance was set at 0.05. Results Monolithic Zirconia Crowns (Group 1) require significantly more force (mean: 405 N) to induce an edge chip compared to Indirect Composite Layered Zirconia Crowns (Group 2) (mean: 300 N). The 95% confidence interval (83.43261 N to 109.90072 N) confirms the statistical significance of this difference. Conclusion In conclusion, when evaluating restorative materials based on both esthetic and functional criteria, monolithic zirconia stands out due to its combination of strength, esthetic potential, biocompatibility, and versatility.

No abstract available

A polymer-infiltrated ceramic network (PICN) material has recently been introduced for dental use and evidence is developing regarding the fit accuracy of such crowns with different preparation designs. The aim of this in vitro study was to evaluate the precision of fit of machined monolithic PICN single crowns in comparison to lithium disilicate crowns in terms of marginal gap, internal gap, and absolute marginal discrepancies. A secondary aim was to assess the effect of finish line configuration on the fit accuracy of crowns made from the two materials. Two master metal dies were used to create forty stone dies, with twenty each for the two finish lines, shoulder and chamfer. The stone dies were scanned to produce virtual models, on which ceramic crowns were designed and milled, with ten each for the four material–finish line combinations (n = 10). Marginal gaps and absolute marginal discrepancies were evaluated at six pre-determined margin locations, and the internal gap was measured at 60 designated points using a stereomicroscope-based digital image analysis system. The influence of the material and finish line on the marginal and internal adaptation of crowns was assessed by analyzing the data using two-way analysis of variance (ANOVA), non-parametric, and Bonferroni multiple comparison post-hoc tests (α = 0.05). ANOVA revealed that the differences in the marginal gaps and the absolute marginal discrepancies between the two materials were significant (p < 0.05), but that those the finish line effect and the interaction were not significant (p > 0.05). Using the Mann–Whitney U test, the differences in IG for ‘material’ and ‘finish line’ were not found to be significant (p > 0.05). In conclusion, the finish line configuration did not seem to affect the marginal and internal adaptation of PICN and lithium disilicate crowns. The marginal gap of PICN crowns was below the clinically acceptable threshold of 120 µm.

No abstract available

No abstract available

No abstract available

The aim of this study was to evaluate the effect of Saudi coffee consumption in comparison to various types of commonly used coffees (instant black, Turkish, and espresso) on the color of novel aesthetic dental ceramics. A total of 144 flat cylindrical discs with an 8-mm diameter and 0.5-mm thickness were created using CAD/CAM technology. Three ceramic materials were used: Lithium disilicate (Emax) and two ultra-translucent monolithic zirconia ceramics; Aidite and Cercon Xt (Cer). The specimens were immersed in six coffee solutions: Saudi coffee from eastern region (ES), Saudi coffee from northern region (SN), Saudi coffee from middle region (SM), instant black coffee (Ne), Turkish coffee (Tk) and espresso coffee (Es). All specimens (n = 8) were immersed for a period of 15 days. The color of all specimens was measured before and after immersion, and the CIE L*a* b* coordinates were obtained with a spectrophotometer. Values for the translucency parameter (TP), contrast ratio (CR) and color change (ΔE) for each specimen were calculated. Data were analyzed using paired sample t-test and one-way ANOVA and post hoc testing. Color coordinates L*, a* and b* significantly changed after immersion in all coffee solutions relative to pre-immersion values, with a noticeable decrease in lightness (L*) (P < .05). A significant color change (∆E) was observed in all tested materials in all coffee solutions after immersion, with ∆E values exceeding 5.26 (P < 0.05). Color changes (∆E) for specimens immersed in the three formulations of Saudi coffee were significantly less than those immersed in the other coffee solutions (P < 0.05). Saudi coffee with formulations from the northern region resulted in more color changes in Emax in comparisons to the other two Saudi coffee formulations from the middle and eastern regions. Aidite and Cer ceramics showed less TP values than Emax. Consumption of coffee for a period of simulated 1 year has significantly altered the color of ceramic materials to a level above the threshold at which the clinical perception of color change occurred (> 3.3). Saudi coffee consumption caused less changes in the color of tested ceramics in comparison to the consumption of commonly used coffees (instant black, turkish, and espresso).

   Relevance. New dental materials made of zirconium dioxide include 3Y-TSP and 5Y-TSP, suitable for various clinical cases, including multilayer systems that create a transparency gradient. After milling, the pre-sintered Y-TZP frames must be subjected to final sintering in 8–10 hours, although modern technologies can reduce it to 17 minutes. However, high-speed sintering can degrade the color and transparency of finished prostheses. The new monolithic ceramic systems have increased the Y3+ content to about 4 and 5 ml. %, but the indicators of layered transparency of multilayer samples after high-speed sintering remain insufficiently studied.   The purpose of the work. The study of layered transparency after traditional and high-speed sintering of domestic multilayer ceramics made of zirconium dioxide and its imported analog using a laboratoryspectrophotometer.   Materials and methods. Groups of 12 samples were studied: the main one (domestic production of «Ziceram ML ET») and the control one (Chinese production of «Aidite 3D Pro»), divided into subgroups «a» (traditional sintering) and «b» (high-speed sintering). The size of all samples is 15×15×1 mm, colors A1–A3, milled by removing plates from a single layer. Subgroups «a» were fired according to traditional modes with an exposure time of 30–120 minutes. Subgroup «b» was baked in a high-speed furnace in 25 minutes. Transparency was assessed using an X-Rite Ci4200 spectrophotometer using the CIE Lab* system, calculating the ratio of the «L» luminance indicators on a white and black background.   Conclusions. The lightness of the layers of multilayer ceramic blanks «Ziceram ML ET» and «Aidite 3D Pro» is significantly reduced after high-speed sintering compared to traditional firing. The transparency gradients of Russian and Chinese multilayer ceramics differ, with significant changes after high-speed sintering.

Abstract Objectives Due to the dynamic character of the stomatognathic system, fatigue life experiments simulating the cyclic loading experienced by implant-supported restorations are critical consideration. The aim of this study was to examine the effect of different crown and abutment materials on fatigue failure of single implant-supported crowns. Methods Models were created for 10 different designs of implant-supported single crowns including two zirconia-reinforced lithium silicates (crystallized and precrystallized), monolithic lithium disilicate, polymer-infiltrated ceramic networks, and polyetheretherketone supported by zirconia and titanium abutments. A cyclic load of 179 N with a frequency of 1 Hz was applied on palatal cusp of a maxillary first premolar at a 30° angle in a buccolingual direction. Results In the models with titanium abutments, the polymer-infiltrated ceramic network model had a lower number of cycles to fatigue failure values in the implant (5.07), abutment (2.30), and screw (1.07) compared to others. In the models with zirconia abutments, the crystallized zirconia-reinforced lithium silicate model had a higher number of cycles to fatigue failure values in the abutment (8.52) compared to others. Depending on the fatigue criteria, polyetheretherketone implant crown could fail in less than five year while the other implant crowns exhibits an infinite life on all models. Conclusions The type of abutment material had an effect on the number of cycles to fatigue failure values for implants, abutments, and screws, but had no effect on crown materials. The zirconia abutment proved longer fatigue lifetime, and should thus be considered for implant-supported single crowns.

The aim of this in vitro study was to evaluate the effects of substrate and cement shades on the translucency and color of lithium-disilicate and zirconia CAD/CAM materials. Two light-cured resin cements (RelyX Veneer Cement; 3M; Choice 2 Veneer Cement; Bisco Dental) with a standardized thickness (0.1 mm) were tested in combination with two different monolithic CAD/CAM materials (E-Max CAD (LI2SI2O5); Ivoclar Vivadent; Katana (ZrO2); Kuraray-Noritake Dental) on two different colored composite substrates used as a dentin (Filtek Supreme XTE; 3M); for a total of 12 combinations (n = 10). The specimens’ color was measured with a spectrophotometer (Spectroshade; MHT). Measurements were taken using the CIELAB color coordinate system (L*a*b*) against black and white backgrounds. L*a*b* values were statistically analyzed for the variables Substrate, Ceramic, and Cement by applying a Three-Way ANOVA followed by the Tukey Test for post-hoc comparison (p < 0.05). Translucency Parameter (TP) and Constant Ratio (CR) were assessed to evaluate translucency; acceptability and perceptibility thresholds (ΔE00 1.8 and 0.8) were used. Statistically significant influence was found for factors ceramic material, cement shade, and substrate color (p < 0.05). Unacceptable color differences were reported for Li2Si2O5. Opacity was significantly higher when white opaque cement shade was employed. Ceramic type and cement shade significantly influenced L*a*b* color coordinates. The final translucency and color of ceramic restorations can, therefore, be influenced by ceramic material, cement shade, and substrate color.

Background: Marginal and internal adaptation are key factors that determine the clinical success of dental restorations. Aim: The aim of this study is to evaluate the marginal and internal fit of crowns fabricated with three different CAD-CAM zirconia materials; two monolithic zirconia materials and one veneered zirconia copings in comparison with conventional metal-ceramic crowns. Material and Methods: Ninety-six extracted molars (n = 96) were selected. Teeth were randomly divided into four groups (n = 24), and the following restorations were fabricated: Metal-ceramic crowns (Control group) (Group CG); monolithic zirconia crowns (GC initial) (Group MZ1); monolithic zirconia crowns (InCoris TZI),(Group MZ2); bilayered zirconia crowns, cores (InCoris ZI) veneered with a low-fusing glass-ceramic (IPS Emax Ceram),(Group BZ). Internal and marginal adaptations were evaluated using the silicone replica technique. A total of 20 points were recorded for every tooth under the light microscope at 20x magnifications. Results were compared using one-way analysis of variance (ANOVA) and the post hoc Tukey's test at a significance level of 0.01. Results: Marginal, marginal-internal, axial, and occlusal gaps between CG, MZ1, MZ2, and BZ crowns showed statistically significant differences (P < 0.01). Conclusion: Monolithic zirconia groups showed better marginal adaptation compared with the veneered zirconia crowns.

Translucency and color stability are key factors for the long-term success of dental ceramics. The aim was to compare the translucency parameter (TP) and color stability (ΔE) of CAD/CAM ceramics, including a lithium disilicate (E; IPS e.max CAD), a zirconia-reinforced lithium-silicate (S; VitaSuprinity), and a zirconia-based ceramic (Z; Ceramill Zolid HT+), before and after low-grade hydrothermal aging (134 °C and 2 bars for 20 h). Ninety disks (n = 30/group, A2, 1.2 ± 0.02 mm) were fabricated and their L*, a*, and b* values were recorded against black and white backgrounds to calculate TP, contrast ratio (CR), and opacity (OP). ANOVA, Bonferroni post hoc, and paired t-tests (α = 0.05) showed that after aging, the Z group showed ↓L and ↑a values; the E group showed ↓L with ↑ a and b; and the S group showed only ↑a. All ceramics exhibited ΔE values below the clinical acceptability threshold of 3.7. E presented the highest TP, whereas Z demonstrated the highest CR and masking ability. Aging significantly increased CR and OP but did not alter TP. Within the limitations of this study, all tested ceramics maintained clinically acceptable shade stability and translucency, with E showing superior initial translucency and Z offering improved masking potential.

Micro-hardness is a fundamental property of prosthodontic restorative materials, as it affects their resistance to surface deformation, wear, and long-term clinical performance. This study aimed to compare the Vickers micro-hardness of three widely used CAD/CAM materials: lithium disilicate, monolithic zirconia, and multilayered zirconia. A total of 30 specimens (N = 30) were fabricated, with 10 samples allocated to each material group. Lithium disilicate specimens were prepared as rectangular plates (18 × 15 × 1 mm), whereas zirconia specimens—both monolithic and multilayered—were fabricated as discs (10 mm in diameter and 1.5 mm in thickness) following standardized CAD/CAM milling and sintering protocols. Vickers micro-hardness testing was conducted using a digital micro-hardness tester under material-specific conditions: a load of 1 kg and a dwell time of 10 s for lithium disilicate, and a load of 500 g with a 20 s dwell time for zirconia. Statistical analysis was performed using one-way ANOVA followed by Tukey’s post-hoc test, with the significance level set at p < 0.05. Significant differences in micro-hardness were identified among the three materials (p < 0.001). Monolithic zirconia demonstrated the highest mean hardness (680 ± 19 HV), followed by multilayered zirconia (623 ± 47 HV), while lithium disilicate exhibited the lowest values (553 ± 32 HV). Post-hoc analysis confirmed that all pairwise comparisons were statistically significant. The findings indicate that monolithic zirconia possesses superior micro-hardness compared to multilayered zirconia and lithium disilicate, supporting its suitability for high-stress clinical applications. Multilayered zirconia offers a balance between mechanical performance and esthetics, whereas lithium disilicate remains optimal for highly esthetic anterior restorations. These results provide clinicians with evidence-based guidance for selecting CAD/CAM materials in fixed prosthodontic rehabilitation.

No abstract available

Objective The purpose of this in vitro study is to compare the flexural strength and Weibull modulus of 5 different monolithic computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics. Methods A total of 50 specimens were fabricated, 10 from each of the following materials: lithium disilicate-based ceramic (IPS e.max CAD), zirconia -reinforced lithium-silicate ceramic (Vita Suprinity), leucite-based glass ceramic (IPS Empress CAD), and two zirconia-based ceramics (Zenostar and CopraSmile). The specimens were 4 mm wide, 2 mm thick, and 16 mm long. Flexural strength test was executed using a universal testing machine (Model 5980, Instron Industrial Products, Norwood, MA, USA). The two-parameter Weibull distribution function was used to analyze the variability of flexural strength values. Statistical analysis was performed on SPSS Version 23 (IBM Corp., Armonk, NY, USA) using one-way analysis of variance (ANOVA) and post-hoc Tukey’s test. Results Suprinity had the highest Weibull modulus value, while Empress CAD displayed the lowest value. One-way ANOVA showed significant difference in the flexural strength between the different materials tested (p<0.05). Post-hoc analysis revealed significant differences among all the test groups in terms of flexural strength. Zenostar presented the highest mean flexural strength value (1033.90 MPa), while Empress CAD had the lowest value. Conclusion High-translucency zirconia had superior flexural properties than translucent zirconia, lithium disilicate ceramics, zirconia-reinforced lithium silicate ceramics, and leucite-based glass ceramics.

Background This study aimed to investigate different surface treatments thought to increase the bond strength between zirconia ceramic and adhesive resin cement. Methods The samples were prepared in 15 × 10 × 2 mm dimensions by cutting off monolithic zirconia ceramic blocks (Incoris TZI; Sirona, Germany). Surface roughness measurements were made with a profilometer, the average surface roughness (Ra1) was recorded, and five different surface treatments were applied. Group 1: Control group. No surface treatment was applied. Group 2: Sandblasted with Al_2O_3 under pressure of 50 μm. Group 3: Sandblasted with 30 μm Al_2O_3 - SiOx under pressure, then tribochemical silica coating, silane bonding agent, and ceramic primer were applied. Group 4: Samples were etched in a hot acid solution containing methanol, HCl, and chloride at 100 °C. Group 5: Samples were coated in a solution containing Grade C Aluminum Nitrite at 75 °C for 15 Sects. 12,000 thermal aging was carried out to all samples. Then, samples were bonded to a composite surface (Filtek Z250) with two different types of adhesive cement (Panavia F 2.0, Rely X U200) (n = 10). A load was applied to the samples attached to the Universal Test Device for the SBS, and the SBS was recorded. The surface roughness measurements of all samples were made again, and the average surface roughness Ra2 was recorded. The data was analyzed with a two-way ANOVA test. Bonferroni correction was used for multiple comparisons of the groups. p  = 0.005 was accepted as the statistically significant value. Results There was no statistically significant difference between the groups in the Ra1 measurements ( p  = 0.031). There was a statistically significant difference between the Ra2 values of Groups 4 and 5 and the Ra2 values of Groups 1,2 and 3 in the Ra2 measurements ( p  < 0.001). There was no statistically significant difference between the SBS values of the groups ( p  > 0.005). Also, there was no statistically significant difference in the SBS values of all groups for the two different cements tested ( p  > 0.005). Conclusions None of the surface treatments applied to monolithic zirconia ceramic samples increased the SBS between ceramic and adhesive resin cement.

PURPOSE To evaluate and compare the fracture mode and strength of monolithic zirconia to veneered zirconia and metal-ceramic full-coverage restorations following artificial aging. The main concern was to test the performance of translucent zirconia in terms of load-bearing capacity. MATERIALS AND METHODS Two mandibular first molars were prepared and scanned for their respective groups of full-coverage restorations. 75 full-coverage restorations were fabricated and divided into five groups: two groups for monolithic zirconia, two groups for veneered zirconia, and one group for metal-ceramic. 75 light-cured hybrid composite resin dies were fabricated to serve as abutments. Before cementation, all full-coverage restorations were subjected to accelerated aging. After cementation, all full-coverage restorations were subjected to compressive loading until fracture in an electromechanical universal testing machine. A two-way nested analysis of variance and Tukey test were used to analyze the results with 95% confidence levels. RESULTS Monolithic zirconia full-coverage restorations showed the highest mean fracture resistance of 4,201 N, followed by metal-ceramic full-coverage restorations of 3,609.3 N, and the veneered zirconia full-coverage restorations showed the lowest of 2,524.6 N. The main mode of failure was cohesive bulk fracture for the monolithic zirconia group, cohesive/adhesive failure along with infrastructure damage for the veneered zirconia group and cohesive/adhesive failure without infrastructure damage for the metal-ceramic group. CONCLUSIONS Monolithic zirconia full-coverage restorations showed superior resistance to fracture in comparison to metal-ceramic full-coverage restorations and are highly reliable in terms of load-bearing capacity within the posterior regions of the mouth.

Abstract Objectives One critical factor that influences clinical outcomes of fixed dental restorations is the internal gaps between the restoration and the abutment tooth. However, investigating these gaps in the context of fabrication processes with new technologies is few. This study compared internal accuracy of sintered versus cast metal substructures upon different fabrication techniques, veneered with layering and press-on ceramic, during different construction stages, at different sites of restoration. Materials and Methods A total of 96 metal substructures were fabricated with a standardized dimension from four techniques: cast metal with traditionally impressed tooth [CmTt], cast metal with digitally milled wax [CmDw], sintered metal with digitally impressed tooth [SmDt], and sintered metal with digitally impressed stone model [SmDm]. They were further subdivided into two subgroups according to the veneering ceramic used [layered (Pl) and press-on (Pp)]. Internal accuracy was evaluated at gingival, gingiva-axial, axial, axio-occlusal, and occlusal locations using silicone replica, after metal coping (As), degassing (De), opaque application (Op), contouring (Co), and glazing (Gl). Statistical Analysis Analysis of variance and Bonferroni tests were analyzed for significant differences of internal fit upon different factors ( α  = 0.05). Results Significantly different internal accuracy was found upon metal substructures fabrication technique, veneering methods, stages, and sites of restoration ( p  < 0.05). SmDt and SmDm revealed significantly better fit than CmTt and CmDw ( p  < 0.05). Pp generated significantly better fit than Pl ( p  < 0.05). Significantly increasing gaps were found upon stages ( p  < 0.05). Occlusal and axio-occlusal sites exhibited larger gaps than axial, gingivo-axial, and gingival sites ( p  < 0.05). However, all groups exhibited clinically acceptable internal accuracy. Conclusion Increasing internal inaccuracies upon stages of fabrication were noticed, with highly observed at the occlusal and axio-occlusal sites. Sintered metal (SmDt, SmDw) provided better accuracy than cast metal (CmTt, CmDw) while press-on veneering generated better accuracy than the layering method. Ceramic press-on sintered metal was suggested for fabrication restoration.

OBJECTIVE The present study aimed to evaluate the accuracy of ceramic copings fabricated by milling, DLP printing, and heat-pressing methods. METHODS A central maxillary incisor coping was designed after scanning a typodont model. Thirty specimens were fabricated using milling (MCC), DLP printing (PCC), and heat-pressing methods (HCC) (n=10). All the specimens were scanned with a lab scanner. The scanned data were segmented into external, internal, and marginal regions and analyzed using 3D measurement software. The accuracy of each group was evaluated and Root mean square (RMS) deviations were calculated. For statistical analysis of the measurements, the Kolmogorov-Smirnov test was conducted to assess the normality and homogeneity of variance among the three groups and the results. As equal variances were not observed (p < 0.05), a nonparametric Kruskal-Wallis test was conducted, followed by post-hoc analysis using the Bonferroni-adjusted Mann-Whitney U test (α = 0.016). RESULTS The MCC group recorded RMS values of 14.29 ± 1.80 µm and 15.80 ± 2.36 µm in the internal and marginal regions, respectively, with lower deviation (p < 0.001). The PCC group showed the highest RMS in the internal region at 39.43 ± 4.59 µm (p = 0.684). The HCC group's RMS value was highest in the external region at 55.53 ± 5.71 µm (p < 0.001). Statistical analyses indicated significant differences in RMS values in external and internal regions but not in the marginal region (p = 0.143). All the RMS values remained within the clinically acceptable range. CONCLUSION This study confirmed that different fabrication techniques significantly influence the dimensional accuracy of ceramic copings. The MCC group showed lower RMS values whereas the PCC and HCC groups exhibited higher RMS values. However, all RMS values remained within the clinically acceptable range. CLINICAL SIGNIFICANCE Clinical Significance: This study assessed the trueness and precision of ceramic copings made by different fabrication methods. The MCC group exhibited the greatest precision in both the internal and marginal regions. In contrast, the PCC group, while requiring additional research and validation in marginal areas, displayed enhanced accuracy and reproducibility in the external region compared to the HCC group. However, further research with newly developed techniques is required.

Objective: To investigate the load-bearing capacity of the full-coverage crowns made from lithium disilicate glass-ceramic LDGC (IPS e.max®, Ivoclar Vivadent) and 10% zirconia reinforced lithium silicate glass ceramic ZLS (Dentsply DeTrey) with different thicknesses. Methods: Forty resin dies with supporting bases were duplicated from two prepared typodont teeth for all-ceramic crowns as a maxillary first molar. Forty crowns corresponding to each die were prepared and then they were divided into four groups: Group I (n 10) made from ZLS with a restoration thickness of (1.0 mm occlusally and 1.0 mm radially) and Group II (n 10) made from LDGC with a restoration thickness of (1.0 mm occlusally and 1.0 mm radially), and Group III (n 10) made from ZLS (1.5 mm occlusally and 1.5mm radially) and Group IV (n 10) made from LDGC (1.5 mm occlusally and 1.5 radially). All crowns were fabricated by chair side CEREC CAD/CAM and crystallized with Speed fire Dentsply Furness. The virolink resin cement (VariolinkII, Ivoclar Vivadent) was used to bond the crowns to the corresponding dies.  All samples were thermo-cycled (10000 cycles between 5c and 55c) and tested for fracture resistance using a Universal testing machine at 0.5 mm/minute speed until failure. ANOVA and Tukey HSD test were used to compare the fracture resistance between groups. Results: The result demonstrates that the fracture resistance means and SD of ZLS with different thicknesses ranged from 572 N ± 122.002 to 1171±217.432 N, and those of LDGC with different thicknesses ranged from 625 N ±151.676 N to 845 N ±388.222 N. Conclusions: The fracture resistance increased with increasing crown thickness using different glass-ceramic materials.

To evaluate the fracture strength and the failure mode of endodontically treated molars restored with monolithic lithium disilicate and zirconia endocrowns and overlays. A total of 48 extracted mandibular molars were endodontically treated, decoronated 2 mm above the cementoenamel junction and divided into four 12-specimen groups. Group ELD: lithium disilicate endocrowns. Group EZ: monolithic zirconia endocrowns. Group OLD: lithium disilicate overlays. Group OZ: monolithic zirconia overlays. Overlays did not extend in the pulp chamber and endocrowns extended in the pulp chamber 2 mm. After adhesive bonding of the restorations, the specimens were subjected to thermocycling (×5000 cycles) and then to fracture resistance testing at lateral static loading (1 mm/min) at a universal testing machine. The failure mode of the specimens was qualitatively evaluated. Differences in means were compared using with t-tests for independent samples or Mann–Whitney test (p < 0.05). Weibull distribution analysis was also performed. Group ELD showed significantly higher fracture strength than all other groups (p = 0.001), and the highest Weibull modulus. Conclusions: Lithium disilicate endocrowns exhibit higher fracture strength and are more reliable compared to the other types of restorations examined. Endocrowns had more catastrophic failures compared to overlays.

STATEMENT OF PROBLEM The necessity of roughening the intaglio surface of zirconia crowns to achieve adequate retention is unclear. PURPOSE The purpose of this clinical simulation study was to evaluate the retention of airborne-particle-abraded and nonabraded monolithic zirconia crowns using 3 different cement types. MATERIAL AND METHODS Extracted human molars were used and prepared with a 10-degree taper. Impressions were made of the prepared teeth with a polyvinyl siloxane (PVS) material, and dies were made with Type 4 gypsum. Each die was scanned with a NobelProcera 1G Scanner, and the standard tessellation language (STL) files were transferred electronically to the Nobel Biocare production site, where a bar was added virtually on top of each crown and parameters were set for milling. Seventy-two Procera zirconia crowns were generated, of which half were airborne-particle abraded on the intaglio surface with 50-µm alumina particles at 400 to 500 kPa for 15 seconds. The other 36 received no intaglio treatment other than cleaning. Both groups of 36 crowns were divided into 3 subgroups of 12 specimens. The area of each preparation was calculated using a computer-aided design software program. The specimens were distributed to attain similar mean surface areas among the cementation groups. The crowns were cemented onto the specimen with a controlled force of 196 N. The 3 cements used were self-adhesive, modified resin RelyX Unicem Aplicap, resin-modified glass ionomer RelyX Luting, and a composite resin, Panavia F2.0 with ED Primer A & B. All specimens were thermocycled (5 °C to 55 °C) for 5000 cycles and then removed axially with a universal testing machine (Instron Model 5585H) at a crosshead speed of 0.5 mm/min. The removal force was recorded, and stress of dislodgement was calculated for each crown. A 2-way analysis of variance was used for statistical analyses. The type of failure was analyzed with the chi-squared test of association for independent samples (α=.05 for all tests). RESULTS The mean dislodging force for crowns with airborne-particle abraded intaglio was 5.4 MPa, which was statistically greater than the mean of 3.2 MPa for nonabraded specimens (P<.001). No significant differences related to the dislodging stresses were detected among the 3 cements (P=.109). The mode of failure was similar whether abraded or not, with 50% of specimens retaining cement in the crown after separation. CONCLUSIONS Alumina airborne-particle abrasion of the intaglio of zirconia to create surface roughness is beneficial in retaining the crowns, regardless of the cement type. The nonabraded crowns demonstrated significantly lower retentive stress with crown removal. The principal mode of failure was similar whether the zirconia intaglio was airborne-particle abraded or not. The most common mode of failure (>50% of specimens) was at least three-fourths of the cement remaining within the crown.

Purpose: The improvement of computer-aided design and computer-aided manufacturing (CAD/CAM) has changed the methods of fabricating laminate veneers. The objectives of this study were to evaluate the marginal and internal fit of ceramic veneers manufactured with different CAD/CAM techniques. Materials and methods: A metal die was made by copying a prepared plastic maxillary central right incisor and scanned for designing a laminate veneer. One hundred laminate veneers were made with four different CAD/CAM techniques (n=25), including milled lithium disilicate (MLD), heat-pressed lithium disilicate with 3-dimensional (3D) printed wax patterns (PLD), milled zirconia (MZ), and 3Dprinted zirconia (PZ). The virtual marginal and internal fit of fabricated veneers was evaluated with digital crown fitting software. The actual marginal and internal fit was measured with the silicone replica method under a digital microscope. The measured data were analyzed using the one-way analysis of variance and the Turkey test. Results: There were significant differences in marginal and internal fit (P < 0.001) among manufacturing techniques. Both the virtual and actual marginal and internal gaps were higher in the PLD and PZ groups compared to the MLD and MZ groups. Conclusion: All four CAD/CAM techniques of manufacturing veneers, that is, milled lithium disilicate, heat-pressed lithium disilicate with 3D-printed wax patterns, milled zirconia, and 3D-printed zirconia, have clinically acceptable marginal and internal fit. Milled zirconia and lithium disilicate veneers demonstrated superior marginal and internal fit compared to 3D-printed zirconia and heat-pressed lithium disilicate veneers with 3D-printed wax patterns.

Advances in computer-aided design (CAD) / computer-aided manufacturing (CAM) technologies and their ease of application enabled the development of novel treatment concepts for modern prosthodontics. This recent paradigm shift in fixed prosthodontics from traditional to minimally invasive treatment approaches is evidenced by the clinical long-term success of bonded CAD/CAM glass-ceramic restorations. Today, defect-oriented restorations, such as inlays, onlays, and posterior crowns, are predominately fabricated from glass-ceramics in monolithic application. The variety of CAD/CAM ceramic restorative systems is constantly evolving to meet the increased demands for highly aesthetic, biocompatible, and long-lasting restorations. Recently introduced polymer-infiltrated ceramic network CAD/CAM blocks add innovative treatment options in CAD/CAM chairside 1-visit restorations. The material-specific high-edge stability enables the CAD/CAM machinability of thin restoration margins. Full-contour zirconia restorations are constantly gaining market share at the expense of bilayered systems. Advancements in material science and bonding protocols foster the development of novel material combinations or fabrication techniques of proven high-strength zirconia ceramics. CAD/CAM applications offer a standardized manufacturing process resulting in a reliable, predictable, and economic workflow for individual and complex teeth-supported restorations. More evidence from long-term clinical studies is needed to verify the clinical performance of monolithic polymer-infiltrated ceramic network and zirconia teeth-supported minimally invasive and extensive restorations.

No abstract

No abstract

No abstract

This study evaluated the wear of computer-aided design/computer-assisted manufacture (CAD/CAM) burs and the morphologic changes after a number of millings. Diamond burs (cylinder and step-bur) were divided into four milling groups: zero millings (G0); 15 millings (G1); 25 millings (G2); and 35 millings (G3). Seventy-five premolar crowns were milled using the Cerec Compact Milling unit and VitaBlock Mark II. Surface roughness, three-dimensional profile, and SEM were used for wear and surface damage evaluation. Two-way ANOVA and Tukey test (α = .05) showed that G3 produced statistically different values compared to G0 and G2, but not G1. The cylinder burs showed higher roughness values than step-burs for all groups. SEM showed similar diamond particle damage for cylinder burs and step-burs, and signs of surface damage, cracks, and particle losses for G3. Both cylinder burs and step-burs were able to sustain a larger number of milling procedures than indicated by the manufacturer.

Recently, the use of computer-aided design/computer-aided manufacturing (CAD/CAM) to produce complete dentures has seen exponential growth in the dental market, and the number of commercially available CAD/CAM denture systems grows every year. The purpose of this article is to describe the clinical and laboratory procedures of 5 CAD/CAM denture systems.

No abstract

Today's range of chairside CAD/CAM blocks is very large and diverse. In addition, manufacturers of new CAD/CAM blocks often advertise with an inappropriate material category. This raises the question of how the reconstructions should ideally be pretreated in order to achieve an optimum bond between the restoration and the tooth structure. Das heutige Angebot an chairside-CAD/CAMBlöcken ist sehr gross und vielfältig. Zudem werben Hersteller neuartiger CAD/CAM-Blöcke oft mit einer nicht zutreffenden Materialkategorie. Entsprechend stellt sich die Frage, wie die Rekonstruktionen idealerweise vorbehandelt werden sollen, um einen optimalen Verbund der Restauration mit der Zahnsubstanz zu erzielen.

No abstract

To evaluate the fatigue failure load (FFL), number of cycles for failure (CFF) and survival probabilities of lithium-disilicate (LD) monolithic crowns manufactured by two processing techniques (pressing vs. CAD/CAM) adhesively cemented to a dentin-analogue material, considering two surface treatments (conventional vs. simplified). Surface characteristics (topography, roughness and fractal dimensions) were also assessed. Forty (40) monolithic crowns were manufactured considering two specific processing techniques for each ceramic system: LD

To report the long-term clinical survival and failure rates of single-tooth restorations made of pressable lithium disilicate ceramics (LS Twenty-one patients (12 female, nine male) were treated with 436 minimally invasive single-tooth restorations made of 274 pressed LS The 274 LS Pressed LS Despite the limitations of the clinical observations, single-tooth restorations of both materials can be recommended for permanent use in patients with severe tooth wear.

The composite luting gap between ceramic and dental hard tissue can be termed an "Achilles heel". Therefore, one major goal of luting ceramics focuses on minimizing the inter-marginal gap area. This study evaluated the marginal accuracy of two all-ceramic systems. The null hypothesis was that there is no statistical difference between the marginal accuracy of the IPS Empress and Cerec 3D all-ceramic systems. On 16 casts, representing different clinical situations, the left first mandibular molar was prepared to receive large onlays (MOD and replacement of the distobuccal and distal cusps). For each cavity, one laboratory heat-pressed (IPS Empress) and one chairside CAD/CAM restoration (Cerec 3D) were manufactured. A newly developed milling unit was used for CAM processing. The restorations were placed in their respective cavities and die replicas were taken and examined under SEM for quantitative gap measurement. The gap width was measured at 11 defined landmarks by two different examiners. An overall gap width of 56 microm (+/- 31 microm) was measured for IPS Empress, compared to the significantly increased value of 70 pm (+/- 32 microm) for Cerec 3D. From a clinical viewpoint, the statistically significant difference between the two systems is not relevant, since both systems still exhibit a clinically acceptable gap width of less than 100 microm.

Subtractive and additive computer-aided design and computer-aided manufacturing (CAD-CAM) wax pattern processing are 2 methods of fabricating a pressed ceramic crown. Whether a subtractive milled wax pattern or a pattern from the micro-stereolithography additive process produces lithium disilicate crowns with better marginal and internal fit is unclear. Ten silicone impressions were made for a prepared canine tooth. Each die received 2 lithium disilicate (IPS e.max) copings, 1 from milled wax blocks and 1 from additive wax. The replica technique was used to measure the fit by scanning electron microscopy at ×80 magnification. Collected data were analyzed using the paired Student t test for the marginal and internal fit. For the occlusal fit, the difference in scores did not follow a normal distribution, and the Wilcoxon signed rank test was used (α=.05). The mean marginal, axial, and occlusal fit showed no significant differences when the 2 CAD-CAM manufacturing processes were compared (P>.05). For the marginal fit, the mean (±SD) values were 105.1 μm ±39.6 with the milled process and 126.2 μm ±25.2 for the additive process. The mean values were 98.1 μm ±26.1 for the axial fit in the milled process and 106.8 μm ±21.2 in the additive process. For the occlusal fit, median values (interquartile interval) were 199.0 μm (141.5 to 269.9) for subtractive manufacturing and 257.2 μm (171.6 to 266.0) for micro-SLA manufacturing. No significant difference was found between the fit of the 2 techniques. The mean values of axial and occlusal median values were 10 and 5 to 6 times greater than machine's nominal values.

The purpose of this study was to evaluate the marginal discrepancy of heat-pressed ceramic veneers manufactured using a CAD/CAM system. The ceramic veneers for the abutment of a maxillary left central incisor were designed using a CAD/CAM software program. Ten veneers using a micro-stereolithography apparatus (AM group), ten veneers using a five-axis milling machine (SM group), and ten veneers using a traditional free-hand wax technique (TW group) were prepared according to the respective manufacturing method. The ceramic veneers were also fabricated using a heat-press technique, and a silicone replica was used to measure their marginal discrepancy. The marginal discrepancies were measured using a digital microscope (×160 magnification). The data were analyzed using a nonparametric Kruskal-Wallis H test. Finally, post-hoc comparisons were conducted using Bonferroni-corrected Mann-Whitney U tests (α=.05). The mean±SD of the total marginal discrepancy was 99.68±28.01 µm for the AM group, 76.60±28.76 µm for the SM group, and 83.08±39.74 µm for the TW group. There were significant differences in the total marginal discrepancies of the ceramic veneers ( The SM group showed a better fit than the AM and TW groups. However, all values were within the clinical tolerance. Therefore, CAD/CAM manufacturing methods can replace the traditional free-hand wax technique.

The purpose of this study was to determine the effect of two extraoral computer-aided design (CAD) and computer-aided manufacturing (CAM) systems, in comparison with conventional techniques, on the marginal fit of monolithic CAD/CAM lithium disilicate ceramic crowns. This is an in vitro interventional study. The study was carried out at the Department of Prosthodontics, School of Dentistry, Prince Sattam Bin Abdul-Aziz University, Saudi Arabia, from December 2015 to April 2016. A marginal gap of 60 lithium disilicate crowns was evaluated by scanning electron microscopy. In total, 20 pressable lithium disilicate (IPS e.max Press [Ivoclar Vivadent]) ceramic crowns were fabricated using the conventional lost-wax technique as a control group. The experimental all-ceramic crowns were produced based on a scan stone model and milled using two extraoral CAD/CAM systems: the Cerec group was fabricated using the Cerec CAD/CAM system, and the Trios group was fabricated using Trios CAD and milled using Wieland Zenotec CAM. One-way analysis of variance (ANOVA) and the Scheffe post hoc test were used for statistical comparison of the groups (α=0.05). The mean (±standard deviation) of the marginal gap of each group was as follows: the Control group was 91.15 (±15.35) µm, the Cerec group was 111.07 (±6.33) µm, and the Trios group was 60.17 (±11.09) µm. One-way ANOVA and the Scheffe post hoc test showed a statistically significant difference in the marginal gap between all groups. It can be concluded from the current study that all-ceramic crowns, fabricated using the CAD/CAM system, show a marginal accuracy that is acceptable in clinical environments. The Trios CAD group displayed the smallest marginal gap.

This in vitro study evaluated the 3D and 2D marginal fit of pressed and computer-aided-designed/computer-aided-manufactured (CAD/CAM) all-ceramic crowns made from digital and conventional impressions. A dentoform tooth (#30) was prepared for an all-ceramic crown (master die). Thirty type IV definitive casts were made from 30 polyvinyl siloxane (PVS) impressions. Thirty resin models were produced from thirty Lava Chairside Oral Scanner impressions. Thirty crowns were pressed in lithium disilicate (IPS e.max Press; 15/impression technique). Thirty crowns were milled from lithium disilicate blocks (IPS e.max CAD; 15/impression technique) using the E4D scanner and milling engine. The master die and the intaglio of the crowns were digitized using a 3D laser coordinate measurement machine with accuracy of ±0.00898 mm. For each specimen a separate data set was created for the Qualify 2012 software. The digital master die and the digital intaglio of each crown were merged using best-fitting alignment. An area above the margin with 0.75 mm occlusal-gingival width circumferentially was defined. The 3D marginal fit of each specimen was an average of all 3D gap values on that area. For the 2D measurements, the marginal gap was measured at two standardized points (on the margin and at 0.75 mm above the margin), from standardized facial-lingual and mesial-distal digitized sections. One-way ANOVA with post hoc Tukey's honestly significant difference and two-way ANOVA tests were used, separately, for statistical analysis of the 3D and 2D marginal data (alpha = 0.05). One-way ANOVA revealed that both 3D and 2D mean marginal gap for group A: PVS impression/IPS e.max Press (0.048 mm ± 0.009 and 0.040 mm ± 0.009) were significantly smaller than those obtained from the other three groups (p < 0.0001), while no significant differences were found among groups B: PVS impression/IPS e.max CAD (0.088 mm ± 0.024 and 0.076 mm ± 0.023), C: digital impression/IPS e.max Press (0.089 mm ± 0.020 and 0.075 mm ± 0.015) and D: digital impression/IPS e.max CAD (0.084 mm ± 0.021 and 0.074 mm ± 0.026). The results of two-way ANOVA revealed a significant interaction between impression techniques and crown fabrication methods for both 3D and 2D measurements. The combination of PVS impression method and press fabrication technique produced the most accurate 3D and 2D marginal fits.

Dental ceramic restorations are widely spread nowadays due to their aesthetics and biocompatibility. In time, the colour and structure of these ceramic materials can be altered by aging processes. How does artificial aging affect the optical and surface roughness of ceramics? This study aims to assess the effect of thermocycling, surface treatments and microstructure upon translucency, opalescence and surface roughness on CAD-CAM and heat-pressed glass-ceramic. Forty-eight samples (1.5 mm thickness) were fabricated from six types of A2 MT ceramic: heat-pressed and milled glass-ceramic (feldspathic, lithium disilicate and zirconia reinforced lithium silicate). The samples were obtained respecting the manufacturer's instructions. The resulted surfaces (n = 96) were half glazed and half polished. The samples were subjected to thermocycling (10,000 cycles) and roughness values (Ra and Rz), colour coordinates (L*, a*, b*) and microstructural analyses were assessed before and after thermocycling. Translucency (TP) and opalescence (OP) were calculated. Values were statistically analysed using ANOVA test (one way). TP and OP values were significantly different between heat-pressed and milled ceramics before and also after thermocycling (

The load-bearing capacity of ultra-thin occlusal veneers made of 3D-printed zirconia were compared to the ones obtained by fabricating these reconstructions by CAD/CAM milling zirconia or heat-pressing lithium-disilicate. On 60 extracted human molars, the occlusal enamel was removed and extended into dentin. Occlusal veneers of 0.5 mm thickness were digitally designed. The specimens were divided into 3 groups (n = 20 each) differing in the restorative material and the fabrication technique of the occlusal veneer. (1) 3DP: 3D-printed zirconia (Lithoz); (2): CAM: milled zirconia (Ceramill Zolid FX); (3) HPR: heat-pressed lithium disilicate (IPS e.max Press). After conditioning procedures, the restorations were adhesively bonded onto the conditioned tooth. Thereafter, all specimens were aged in a chewing simulator by exposure to cyclic fatigue and temperature variations. Subsequently the specimens were statically loaded and the load which was necessary to decrease the maximum load by 20% and initiate a crack (F The median F Regarding their load-bearing capacity, 3D-printed or milled zirconia as well as heat-pressed lithium disilicate can be recommended as restorative material for ultra-thin occlusal veneers to prosthetically compensate for occlusal tooth wear. Despite statistically significant differences between the restoration materials, all load-bearing capacities exceeded the clinically expected normal bite forces.

The CICERO method of crown fabrication consists of optically digitizing a gypsum die, designing the crown layer buildup, and subsequently pressing, sintering, and milling consecutive layers of a shaded high-strength alumina-based core material, a layer of dentin porcelain, and a final layer of incisal porcelain. Final finishing is performed in the dental laboratory. The CICERO method allows efficient production of all-ceramic restorations without compromising esthetics or function. This article reviews the process involved in the fabrication of a CICERO crown.

To compare the fracture load and failure mode of the monolithic lithium disilicate crown (e.max group) and 2 types of veneered zirconia crowns, hand layer (ZV group) and heat pressed (ZP group), as a posterior implant-supported restoration. A total of 24 all-ceramic crowns for molar tooth were fabricated using the computer-aided design/computer-assisted manufacture (CAD/CAM) system. The e.max group crowns and zirconia copings for ZV and ZP groups were fabricated using a Cerec milling unit. The ZV group was fabricated using a hand-layer veneering method, and the ZP group using a heat-pressing method. All crowns were luted to the abutments, which were connected to implant fixtures, using resin cement. Fracture load was measured using the universal testing machine, and the fracture surface was evaluated by scanning electron microscopy. The ZP group showed significantly higher fracture load (5229.3 N) compared with the e.max group (3852.1 N) and ZV group (3100.3 N). All fractures in the ZV group occurred in the veneered layer. Monolithic CAD/CAM lithium disilicate crowns are applicable to posterior implant-supported restorations because the fracture load was higher than the average occlusal force.

This study aimed to compare the failure load of heat-pressed versus milled lithium disilicate endocrowns. Twenty extracted mandibular molars were sectioned 1.5 mm above the CEJ. Root canal treatment and endocrown preparation were done for all teeth. Samples were then divided into two groups: heat-pressed glass ceramic endocrowns (HP group) (n = 10) and milled endocrowns (CAD group) (n = 10). Cementation was done using self-adhesive resin cement, and a compressive load was applied on the occlusal surface of the specimens until failure occurred. The mean failure loads were significantly higher in the HP group (2546.5 ± 339 N) compared to the CAD group (1759.9 ± 114.2) (p < 0.05), and majority of failures were due to fracture of the restoration. Failure loads of heat-pressed lithium disilicate endocrown are superior to milled endocrown. Molars restored with lithium disilicate endocrowns have higher failure loads than the maximum human bite force regardless of the fabrication method. Although heat-pressed endocrowns have superior failure loads to milled ones, both are indicated for restoring endodontically treated molar teeth.

To apply fracture mechanics methodology to determine the interfacial fracture toughness of the interfaces present in "CAD-on" crowns consisting of CAD/CAM milled lithium disilicate veneers glass-fused to CAD/CAM milled yttrium oxide stabilized tetragonal zirconia polycrystal framework. The notchless triangular prism specimen fracture toughness test was used to determine interfacial fracture toughness. Four groups, each consisting of (6 × 6 × 6 × 12) mm prisms (n = 22), were produced. Half-size [(6 × 6 × 6 × 6) mm] specimens of IPS e.max CAD and IPS e.max ZirCAD were approximated under vibration with Crystal Connect fusing glass and sintered according to manufacturer's guidelines to obtain the following three interfaces: (1) e.max CAD/Crystal Connect/e.max CAD (Group I); (2) Zir CAD/Crystal Connect/Zir CAD (Group II); and (3) Zir CAD/Crystal Connect/e.max CAD (Group III). For Group IV (control, based on the "press-on" veneering technique), half-size [(6 × 6 × 6 × 6) mm] IPS e.max ZirCAD prisms were coated with ZirLiner and pressed with IPS e.max ZirPress ingots to obtain (6 × 6 × 6 × 12) mm prisms. All specimens were tested using a computer controlled material testing machine. Results were analyzed with one-way ANOVA, Scheffé multiple means comparisons (α = 0.05) and Weibull statistics. All fractured surfaces were characterized with a light microscope. Selected fractured surfaces were characterized under a scanning electron microscope. All experimental groups demonstrated a cohesive mode of failure in the fusing glass layer. The number and size of defects appeared to correlate with the variability of fracture toughness values. There were no significant differences between the fracture toughness of the "CAD-on" interfaces (p = 0.052). The results suggested that the fracture toughness of Crystal Connect limited the interfacial fracture toughness values. The "CAD-on" fracture toughness value (Group III) was significantly greater than that of the ZirPress "press-on" control (Group IV) (p < 0.001). The "CAD-on" process results in stronger bonding between veneer and framework, compared to conventional veneering. The clinical use of "CAD-on" crowns could therefore be advocated. The selection of any restorative material requires a thorough analysis of advantages, limitations and results from clinical studies to inform the clinical decision in a case-by-case approach.

To determine the mechanical properties of a newly-developed CAD/CAM resin composite block and compare with other resin composite blocks and a polymer-infiltrated ceramic block. Experimental composite block was formulated by our proprietary resin and filler technologies and cured via Hot Isostatic Pressing (HIP). Bar-shaped specimens (1 × 4×12 - 13 mm, n = 10) for flexural strength, flexural modulus and modulus of resilience were sectioned from block materials and measured in accordance to modified ISO-6872. Cylinder specimens for compressive strength (2 × 4 mm, n = 8) and for diametral tensile strength (6 × 3 mm, n = 8) were milled from the block materials and tested according to ASTM-D695 and ANSI/ADA-Specification #27, respectively. Block specimens (5 mm, n = 3) for Vickers hardness were polished and measured for five indentations on each specimen. The data was analyzed by one-way ANOVA and post-hoc Tukey tests (p ≤ 0.05). Experimental composite block showed higher or significantly higher flexural strength, flexural modulus, modulus of resilience, compressive strength, diametral tensile strength and Vickers hardness than the other commercially available block materials except Vita Enamic for flexural modulus and hardness and Cerasmart for modulus of resilience. Some positive correlations were observed among the different mechanical properties. New composite block exhibited higher mechanical properties as compared to commercially available composite block materials. Superior mechanical properties for resin composite block materials were obtained by composite and curing processing technologies. Resin composite blocks with higher mechanical properties are good options for the fabrication of CAD/CAM indirect restorations.

The use of resin patterns to produce partial coverage restorations is poorly documented. The purpose of this in vitro study was to compare the marginal and internal fit accuracy of lithium disilicate glass-ceramic inlays obtained from wax or resin patterns and fabricated with digital and conventional techniques. A dentoform mandibular first molar was prepared for a mesio-occlusal ceramic inlay. Six groups of 15 inlays were obtained by conventional impression and manual wax (group CICW) or resin patterns (group CICR); conventional impression, laboratory scanning of the stone die, CAD-CAM milled wax (group CIDW), or polymethylmethacrylate (PMMA) blocks (group CIDR); and scanning of the master preparation with an intraoral scanner, CAD-CAM milled wax (group DSDW), or PMMA blocks (DSDR). The same design was applied to produce the wax and PMMA patterns in the last 4 groups. The replica technique was used to measure marginal and internal fit under stereomicroscopy. Mixed-model ANOVA was applied to assess differences according to the techniques, materials, and discrepancy location (α=.05). The results demonstrated significant effects of the technique (P<.001), material (P=.009), and discrepancy location (P<.001) on fit measurements. Marginal discrepancy was only affected by the technique (P<.001), with the digital approaches yielding the smallest marginal discrepancy (23.5 ±3.6 μm), followed by the conventional digital techniques (31.1 ±5.6 μm) and finally by the conventional (42.8 ±7.2 μm) techniques. Internal fit was significantly influenced only by the material with lower discrepancy in wax (75.2 ±9.0 μm) than in resin patterns (84.7 ±15.1 μm). The internal discrepancy was significantly larger than the marginal discrepancy in all groups (P<.001). Inlays generated from conventional wax and resin patterns tend to show higher marginal discrepancies than conventional digital and full digital patterns. Wax and resin materials yield similar marginal fit accuracies irrespective of the impression/manufacturing technique. Better internal fit was shown in wax than in resin patterns, regardless of the technique.

The marginal and internal adaptations of porcelain laminate veneers (PLVs) are key elements in their long-term success. However, the marginal and internal fit obtained with a pressable material compared with computer-aided design and computer-aided manufacturing (CAD-CAM) needs further investigation as does the choice of cement used. The purpose of this in vitro study was to evaluate the marginal and internal fit of PLVs fabricated using pressing and CAD-CAM milling and cemented using 2 types of composite resin cement. Twenty PLVs were fabricated from VITA PM9 pressable material, and 20 veneers were milled using VITA Blocs Mark II. Veneers were cemented to composite resin dies using either RelyX Veneer cement or Variolink-N cement. Specimens were embedded in clear resin and sectioned incisogingivally and mesiodistally. Marginal discrepancy at the incisal and cervical positions and the internal gap at 6 different locations were evaluated by using a scanning electron microscope. Two-way ANOVA followed by Tukey multiple comparisons were used to examine difference among groups (α=.05). The cement and fabrication methods did not show any significant effect for absolute marginal gap (AMG) at the incisal edge, AMG at the cervical margin or marginal gap at the incisal edge. However, both had a significant effect on marginal gap at the cervical margin (P=.038 for the fabrication method and P=.050 for the cement used). Also, both cement and fabrication methods had a significant effect on internal gap average (P<.001). The lowest gap values were reported for veneers fabricated from VITA PM9 by using the press technique and cemented with RelyX Veneer cement. When the position of gap measurements was taken into consideration, it was the only significant factor (P<.001 for the effect of position on AMG and P<.001 for the effect of position on marginal gap). Gaps at the cervical position were significantly lower than gaps at the incisal position. Smaller marginal and internal discrepancies were recorded for PLVs fabricated by using the pressing technique and cemented using RelyX Veneer cement compared with milled veneers and Variolink-N cement. Larger discrepancies were present incisally than cervically.

This study aims to compare the marginal and internal fit of lithium disilicate endocrowns produced by conventional and/or digital impression and fabrication techniques. Endocrown preparations were performed on 40 mandibular first molars. The teeth were divided into four groups (n = 10) based on the impression and fabrication technique; CON: conventional impression/manuel wax patterns/heat-pressed endocrowns, DCD: digital impression/CAD-CAM milled wax patterns/heat-pressed endocrowns, D3D: digital impression/3D printed resin patterns/heat-pressed endocrowns, DC: digital impression/digital design/CAD-CAM milled endocrowns. The marginal and internal fits of the endocrowns were measured by using the silicon replica technique and stereomicroscope with 57x magnification. The statistical analysis was carried out using the Kruskal-Wallis and paired two-sample t-tests. The significance level was set at p < 0.05. Marginal fit measurements revealed the following; CON: 111 μm, DCD: 96 μm, D3D: 91 μm, and DC: 93 μm. A statistically significant difference was found between the CON group and the other groups in the marginal fit measurement. Internal fit measurements revealed the following; CON: 120.75 μm, DCD: 112 μm, D3D: 114.88 μm, and DC: 122 μm. There was a statistically significant difference between the CON group and the DCD group in the internal fit measurement, while no significant difference observed between the other groups. It is concluded that all endocrowns had a clinically acceptable marginal and internal fit. The use of digitally generated patterns, CAD-CAM milled or 3D printed, in the fabrication of endocrowns can be effective in producing restorations with improved marginal and internal adaptation. The use of digital production methods can improve the marginal and internal adaptation of endocrown restorations.

The aim of this systematic review was to assess and compare the clinical performance, marginal adaptation, esthetic outcomes, and long-term survival of lithium disilicate veneers fabricated using computer-aided design and computer-aided manufacturing (CAD/CAM) and heat-pressed techniques. An electronic search was performed in PubMed, Scopus, and Cochrane Library databases on February 24, 2025. Keywords and MeSH terms related to "lithium disilicate," "CAD/CAM," "pressed veneers," "anterior teeth," and "laminate veneers" were used to identify relevant studies published between 2013 and 2025. This review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines and was registered in the International Prospective Register of Systematic Reviews (PROSPERO Registration number; CRD420251003590). Randomized controlled trials, clinical trials, retrospective studies, case series, and ex vivo studies published in English were included. Eligible studies evaluated lithium disilicate veneers placed on anterior teeth with a minimum follow-up of 6 months and reported outcomes related to marginal adaptation, survival, esthetics, or patient satisfaction. Data extraction was performed by two reviewers independently. Risk of bias was assessed using the ROB 2.0, QUIN, and ROBINS-I tools, and the GRADE framework was employed to evaluate the quality of evidence. A total of 401 records were retrieved, out of which eight studies were included after screening. Of these, five studies compared CAD/CAM and heat-pressed veneers, two evaluated CAD/CAM-only, and 3 focused on heat-pressed-only interventions. Two were ex vivo studies. Heat-pressed veneers demonstrated superior marginal adaptation in both clinical and laboratory settings. CAD/CAM veneers showed better internal fit and workflow efficiency. Long-term survival (up to 10 years) was higher in heat-pressed veneers, particularly in complex cases like fluorosis or anterior FPDs. Color match (ΔE values) was within clinically acceptable limits across all materials. Only one randomized controlled trial exhibited low risk of bias; the remaining studies ranged from moderate to high risk. GRADE assessment downgraded most outcomes to low or very low certainty due to study design limitations and heterogeneity. Both CAD/CAM and heat-pressed lithium disilicate veneers offer satisfactory esthetic and clinical outcomes when proper case selection and bonding protocols are followed. While CAD/CAM techniques enhance reproducibility and efficiency, heat-press methods appear superior in marginal adaptation and long-term survival. Further well-designed randomized trials with standardized outcome measures are essential to strengthen current evidence.

Classification systems for all-ceramic materials are useful for communication and educational purposes and warrant continuous revisions and updates to incorporate new materials. This article proposes a classification system for ceramic and ceramic-like restorative materials in an attempt to systematize and include a new class of materials. This new classification system categorizes ceramic restorative materials into three families: (1) glass-matrix ceramics, (2) polycrystalline ceramics, and (3) resin-matrix ceramics. Subfamilies are described in each group along with their composition, allowing for newly developed materials to be placed into the already existing main families. The criteria used to differentiate ceramic materials are based on the phase or phases present in their chemical composition. Thus, an all-ceramic material is classified according to whether a glass-matrix phase is present (glass-matrix ceramics) or absent (polycrystalline ceramics) or whether the material contains an organic matrix highly filled with ceramic particles (resin-matrix ceramics). Also presented are the manufacturers' clinical indications for the different materials and an overview of the different fabrication methods and whether they are used as framework materials or monolithic solutions. Current developments in ceramic materials not yet available to the dental market are discussed.

To compare the fracture load of zirconia and lithium disilicate crowns prepared with endodontic access with fine and coarse diamond instruments. 0.8 mm (3Y zirconia) or 1 mm (lithium disilicate) crowns were luted to resin composite dies with resin-modified glass ionomer (zirconia) or self-adhesive resin (lithium disilicate) cement. A 2.5 mm endodontic access hole was placed in each crown with fine (8369DF.31.025FOOTBALL) or coarse (6379 DC.31.023FOOTBALL) diamond instruments and restored with composite. A control group was prepared without access holes. Crowns were thermocycled for 10,000 cycles (5-55°C) and tested in compression with a steel indenter until failure (n = 8/group). A one-way ANOVA and Dunnett 2-sided test (alpha = 0.05) compared differences in fracture load between groups. For zirconia, there was no statistical difference between the control group (2335 ± 160 N) and coarse diamond group (2345 ± 246 N); however, the fine diamond group (2077 ± 216 N) was significantly lower. For lithium disilicate, there was no statistical difference between the control group (2113 ± 183 N) and the fine (2049 ± 105 N) or coarse (2240 ± 118 N) groups. 3Y zirconia crowns became weaker when accessed with a fine diamond instrument. There was no negative effect of the endodontic access with bonded lithium disilicate crowns. Conservative endodontic access openings in high-strength ceramic restorations do not have a negative effect on their static fracture load. The coarse zirconia-cutting diamond rotary instrument is more efficient and has a less detrimental effect on the strength of the crowns than a fine diamond rotary instrument.

To evaluate the reliability and failure modes of ultrathin (0.5 mm) lithium disilicate, translucent and ultra-translucent zirconia crowns for posterior teeth restorations. Fifty-four mandibular first molar crowns of three ceramic materials: (1) Lithium disilicate (e.max CAD, Ivoclar Vivadent), (2) 3Y-TZP (Zirconn Translucent, Vipi), and (3) 5Y-PSZ (Cercon XT, Dentsply Sirona), with 0.5 mm of thickness were milled and cemented onto composite resin abutments. Eighteen samples of each group were tested under mouth-motion step-stress accelerated life testing in a humid environment using mild, moderate, and aggressive profiles. Data was subjected to Weibull statistics. Use level curves were plotted and reliability was calculated for a given mission of 100,000 cycles at 100, 200, and 300 N. Fractographic analyses of representative samples were performed in scanning electron microscope. Beta (β) values suggest that failures were dictated by material's strength for lithium disilicate and by fatigue damage accumulation for both zirconias. No significant differences were detected in Weibull modulus and characteristic strength among groups. At a given mission of 100,000 cycles at 100 N, lithium disilicate presented higher reliability (98% CB: 95-99) regarding 3Y-TZP and 5Y-PSZ groups (84% CB: 65%-93% and 79% CB: 37&-94%, respectively). At 200 N, lithium disilicate reliability (82% CB: 66%-91%) was higher than 5Y-PSZ (20% CB: 4%-44%) and not significantly different from 3Y-TZP (54% CB: 32%-72%). Furthermore, at 300 N no significant differences in reliability were detected among groups, with a notable reduction in the reliability of all materials. Fractographic analyses showed that crack initiated at the interface between the composite core and the ceramic crowns due to tensile stress generated at the intaglio surface. Ultrathin lithium disilicate crowns demonstrated higher reliability relative to zirconia crowns at functional loads. Lithium disilicate and zirconia crown's reliability decreased significantly for missions at higher loads and similar failure modes were observed regardless of crown material. The indication of 0.5 mm thickness crowns in high-load bearing regions must be carefully evaluated. Ultraconservative lithium disilicate and zirconia crowns of 0.5 mm thickness may be indicated in anterior restorations and pre-molars. Their clinical indication in high-load requirement regions must be carefully evaluated.

Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) restorations of different formulations are being used increasingly in monolithic form for a range of clinical applications. Using rotary instruments to remove such restorations for any purpose is challenging, but they can be removed conservatively with erbium lasers. However, studies on how a laser penetrates different zirconias to break the cement bond between the tooth surface and the zirconia are lacking. The purpose of this in vitro study was to evaluate and compare the time required for an erbium-doped yttrium-aluminum-garnet (Er:YAG) laser to remove different types of zirconia and lithium disilicate crowns. Forty extracted premolar teeth were prepared, scanned, designed, and milled to fabricate 40 computer-aided design and computer-aided manufacturing (CAD-CAM) crowns, which were assigned to 4 groups (n=10): 3 mol% Y-TZP, 4 mol% Y-TZP, 5 mol% Y-TZP, and lithium disilicate as a control. All crowns were bonded to the teeth with a self-adhesive resin cement (Panavia SA Cement Universal). Each specimen was irradiated with an Er:YAG laser with the following parameters: 300 mJ, 15 Hz, 5.0 W, and a 50-microsecond pulse duration (supershort pulse mode). The irradiation time required for crowns to be retrieved successfully was recorded for each specimen. Data were statistically analyzed using analysis of variance and the Tukey honestly significant difference post hoc test (α=.05). The intaglio surfaces of the restorations were analyzed using scanning electron microscopy (SEM). The mean ±standard deviation times in minutes needed for crown debonding were 12.46 ±4.17 for the 3 mol% Y-TZP group, 10.30 ±3.33 for the 4 mol% Y-TZP group, 4.03 ±1.62 for the 5 mol% Y-TZP group, and 2.08 ±0.92 for the lithium disilicate group. A statistically significant difference (P<.05) in the debonding time was found for all investigated groups, expect between the 3 mol% and 4 mol% Y-TZP groups and between the 5 mol% Y-TZP and lithium disilicate groups. SEM analysis of the ceramic surfaces showed no visual damage associated with Er:YAG laser irradiation. Zirconia crown retrieval time with the Er:YAG laser was influenced by the yttria content of the zirconia, with decreasing retrieval time with increasing yttria content. Er:YAG laser debonding of zirconia crowns is a noninvasive, efficient, and rapid approach to the removal of crowns and could be applied in clinical practice.

To evaluate the fracture resistance of a newer lithium disilicate abutment material. A premolar-shaped implant crown was designed using CAD/CAM software, and four groups of implant and crown combinations were milled: (1) lithium-disilicate hybrid-abutment crown; (2) "screwmentable" lithium-disilicate hybrid abutment/lithium-disilicate crown with screw channel; (3) lithium-disilicate hybrid abutment/lithium-disilicate crown; and (4) zirconia hybrid abutment/lithium-disilicate crown (control). The specimens were cemented to a titanium-base implant system, subjected to thermocycling and cyclic loading, and fractured in a material testing device. The lithium-disilicate hybrid-abutment crown had significantly greater fracture load than all the other groups, which were not significantly different from each other. Based on fracture load, the new lithium-disilicate hybrid-abutment material may serve as a viable alternative to the use of zirconia as a hybrid-abutment material.

The objective of this study was to define the impact of heating rate on the crystal growth, the mechanical properties, and the biocompatibility of three different kinds of CAD/CAM glass-ceramics treated with a conventional furnace. Lithium disilicate (IPS EMax-CAD, Ivoclar Vivadent) (LS The crystals' mean size (±SD) after heat treatment was 1650.0 (±340.0) nm for LS All the CAD/CAM materials can be properly crystallized if heat treated following the manufacturers' instructions. The crystallization process highly depends on temperature. ZLS glass ceramics show significantly inferior crystals dimensions and higher fracture toughness and Vickers hardness than LS The value of this study relies on the demonstration that a proper heat-treatment of CAD/CAM lithium disilicate and ZLS glass ceramics generates products that are suitable for clinical use . The differences highlightable in mechanical properties and biocompatibility behavior do not affect their successful clinical application.

In recent years, high esthetic expectations and natural appearance demands from patients have increased the popularity of ceramic restorations. The purpose of this study was to investigate the influence of restoration thicknesses and different resin cement brands on the translucency and final color of different types of monolithic zirconia and lithium disilicate ceramics. A total of 160 disc-shaped specimens (10-mm diameter; 1 mm, or 1.5 mm thick) were produced using different types of monolithic zirconia (Katana Zirconia UTML, Katana Zirconia ML, Katana Zirconia STML Blocks; Kuraray) and lithium disilicate ceramic (IPS e.max Press, Ivoclar Vivadent) (n = 40 discs per material, with 20 discs per thickness). Two different brands of dual-cured resin cements (RelyX Ultimate, 3M ESPE; and BisCem, Bisco) were applied to the specimen surfaces. The translucency and color changes of the lithium disilicate and monolithic zirconia ceramics were examined before and after cementation using a spectrophotometer. Within the limitations of this in vitro study, the resin cement brand and ceramic thickness variation influenced the translucency and final color of the monolithic zirconia and lithium disilicate ceramic specimens.

This in vitro study aimed to evaluate the adhesive performance of zirconia and lithium disilicate Maryland cantilever restorations on prepared and non-prepared anterior abutment teeth. While conventional clinical protocols involve abutment tooth preparation, no-preparation (no-prep) restorations have emerged as a viable, minimally invasive alternative. This study compared the adhesion fracture resistance (N) of zirconia restorations on non-prepared enamel surfaces with those on prepared surfaces exposing the dentin. Additionally, the zirconia restorations were compared with lithium disilicate Maryland cantilever restorations, a more common yet costly alternative. Forty extracted anterior teeth were allocated into four groups based on preparation type (prepared vs. non-prepared) and material (zirconia vs. lithium disilicate). Each group received cantilevered single-unit FPDs fabricated via CAD/CAM and adhesively cemented using Variolink The fracture resistance ranged from 190 to 447 N in the zirconia groups and from 219 to 412 N in the lithium disilicate groups. When comparing all the zirconia versus all the lithium disilicate ceramic restorations, regardless of tooth preparation, no statistically significant difference was found ( Both zirconia and lithium disilicate Maryland cantilever restorations demonstrated reliable adhesive performance when bonded using appropriate surface conditioning and adhesive protocols. Interestingly, the non-prepared designs exhibited higher fracture resistance than the prepared abutments, highlighting their potential advantage in minimally invasive restorative dentistry. Zirconia Maryland bridges, in particular, represent a cost-effective and mechanically resilient option for anterior single-tooth replacement.

To evaluate the influence of anterior monolithic zirconia and lithium disilicate thickness on polymerization efficiency of dual-cure resin cements. Twelve ceramic disks (4.0-mm diameter) with thicknesses of 0.5, 1, 1.5, 2, 2.5, and 3 mm were prepared from monolithic zirconia (Prettau® Anterior; n = 6) and lithium disilicate (IPS e.max® CAD HT; n = 6). Three dual-cure resin cements (Panavia F 2.0, DuoLink Universal™, and RelyX™ U200) were used for polymerization beneath ceramic disks. For each resin cement, 10 specimens were prepared by light curing under monolithic zirconia and lithium disilicate disks of each thickness. Vickers hardness measurements were conducted at four different measurement depths. Data were statistically analyzed using univariate four-, three-, two-, and one-way analysis of variance and independent samples t-tests. Microhardness of resin cements decreased significantly with increasing measurement depth and thickness of monolithic zirconia or lithium disilicate (P < .001). Cements polymerized under lithium disilicate showed higher microhardness values than did those polymerized under zirconia (P < .001). For both ceramics, Panavia F 2.0 exhibited the greatest microhardness, followed by DouLink Universal and RelyX™ U200 (P < .001). Different dual-cure resin cements may have different polymerization efficiencies, and the type and thickness of the overlying ceramic can influence polymerization. The findings of this study suggest that an increase in the thickness of monolithic lithium disilicate or anterior monolithic zirconia restorations can significantly decrease the microhardness of the dual-cure resin cement polymerized beneath the restoration. Dual-cure resin cements can be used for the cementation of anterior monolithic zirconia restorations up to 2 mm thickness and for monolithic lithium disilicate restorations up to 2.5 mm thickness. However, for lithium disilicate restorations with a ≥2.5 mm thickness and zirconia restorations with a ≥2-mm thickness, different cementation approaches must be further studied, such as: extended light curing; the use of dual-cure resin cement with a higher self-curing component than the ones used in this study; or a self-cure resin cement.

Recently, a novel technique was introduced to combine lithium disilicate and zirconia into one restoration. The purpose of this study was to compare the microtensile bond strength of veneering ceramic to a zirconia core in two techniques: the e.max® CAD-on technique and the Press-on technique. Group A was prepared by veneering sintered zirconia blocks (e.max® ZirCAD) with lithium disilicate blocks (e.max® CAD) using the CAD-on technique according to manufacturer's instructions. Group B was prepared by taking sintered e.max® ZirCAD blocks and veneering them with fluorapatite glass-ceramic (e.max® ZirPress) using the Press-on technique according to manufacturer's instructions. Each block was loaded in a dynamic cyclic loading machine. The blocks were then sectioned into 1 × 1 mm(2) beams (n = 43) using a precision saw, thermocycled, and loaded in tension until failure on a universal testing machine. A mean and standard deviation were determined per group. Data were analyzed using an unpaired t-test (α = 0.05). The mean microtensile bond strengths were 44.0 ± 13.8 MPa for the CAD-on technique and 14.9 ± 8.8 MPa for the Press-on technique. Significant differences were found between the two groups (p = 2.7E-19). The CAD-on technique (lithium disilicate/zirconia) resulted in greater microtensile bond strength than the Press-on technique (fluorapatite glass-ceramic/zirconia).

Computer-aided design and computer-aided manufacturing (CAD-CAM) technology and the improved translucency of recently developed high-strength monolithic zirconia could make them clinically acceptable for veneers if bonding to zirconia was as predictable as to glass-ceramics. Few studies have compared how resin cements behave between glass-ceramic and zirconia veneers before and after polymerization. The purpose of this in vitro study was to evaluate the volumetric polymerization shrinkage of resin cement, marginal discrepancy, and cement thickness before and after polymerization for glass-ceramic and zirconia veneers with light-polymerizing resin cement. Ten lithium disilicate veneers and 10 zirconia veneers were fabricated with a CAD-CAM workflow on extracted human maxillary anterior teeth with intact enamel surfaces. Zirconia veneers were treated with airborne-particle abrasion, and lithium disilicate veneers were etched with 5% hydrofluoric acid. All specimens were treated with ceramic primer and cemented with a light-polymerized resin cement. All specimens were scanned before and after resin cement polymerization by microcomputed tomography. The data were processed by the Amira software program to compare polymerization volumetric shrinkage, cement thickness, and marginal discrepancy. The data were compared by using a t test and analysis of variance (α=.05). Two bonded veneers were loaded in a mastication simulator for 400 000 cycles to investigate the effect of cyclic fatigue loading. Mean volumetric polymerization shrinkage was 4.2 ±0.8% for the lithium disilicate group and 6.4 ±3.5% for the zirconia group. No significant difference was found for volumetric shrinkage between materials (P=.132). The mean ±standard deviations of the marginal discrepancies before and after polymerization were 178 ±41 μm and 158 ±37 μm for lithium disilicate and 115 ±33 μm and 107 ±32 μm for zirconia. A smaller marginal discrepancy was found for both materials after polymerization (P=.011) and for zirconia compared with lithium disilicate (P=.004). The mean ±standard deviation cement thickness values before and after polymerization were 157 ±27 μm and 147 ±27 μm for lithium disilicate and 162 ±53 μm and 147 ±52 μm for zirconia. Smaller cement thickness was found after polymerization (P<.001), whereas no significant difference was found in cement thickness between materials (P=.144). No changes were noted in marginal discrepancy and cement thickness as a result of the fatigue loading. The difference in the volumetric polymerization shrinkage of cement between lithium disilicate and zirconia veneers was not statistically significant. Polymerization shrinkage resulted in smaller marginal discrepancy and cement thickness for both veneer materials.

To compare the wear and opposing enamel wear of adjusted (A); adjusted and polished (AP); and adjusted and glazed (AG) zirconia and lithium disilicate. Specimens (n=8) were prepared of lithium disilicate (A, AP, and AG), zirconia (A, AP, and AG), veneering porcelain, and enamel (control). Surface roughness was measured for each ceramic. In vitro wear was conducted in the UAB-chewing simulator (10 N vertical load/2mm slide/20 cycles/min) with lubricant (33% glycerin) for 400,000 cycles. Isolated cusps of extracted molars were used as antagonists. Scans of the cusps and ceramics were taken at baseline and 400,000 cycles with a non-contact profilometer and super-imposed to determine wear. Data were analyzed with ANOVA and Tukey-Kramer post hoc tests (alpha=0.05). A and AP zirconia showed no detectable signs of wear, and the veneering porcelain demonstrated the most wear. All other ceramics showed significantly less volumetric loss than the veneering porcelain, comparable to enamel-enamel wear. Veneering porcelain produced the most opposing enamel wear (2.15 ± 0.58 mm(3)). AP lithium disilicate and zirconia showed the least amount of enamel wear (0.36 ± 0.09 mm(3) and 0.33 ± 0.11 mm(3) respectively). AG lithium disilicate had statistically similar enamel wear as AP lithium disilicate, but A lithium disilicate had more enamel wear. A and AG zirconia had more enamel wear than AP zirconia. No statistically significant difference was seen between the enamel-enamel group and any other group except the veneering porcelain. Zirconia has less wear than lithium disilicate. Wear of enamel opposing adjusted lithium disilicate and zirconia decreased following polishing. Zirconia experiences less and lithium disilicate experiences equivalent occlusal wear as natural enamel. It is preferable to polish zirconia and lithium disilicate after adjustment to make them wear compatible with enamel. Veneering of zirconia and lithium disilicate should be avoided in areas of occlusal contact to prevent enamel wear.

The present study evaluated the fatigue behavior of monolithic translucent zirconia polycrystals (TZ) and lithium disilicate glass-ceramic (LD) bonded to different substrates. Disc-shaped specimens of ceramic materials TZ and LD were bonded to three substrates with different elastic modulus (E) (fiber-reinforced composite (FRC) - softest material, E = 14.9 GPa; titanium alloy (Ti) - intermediary properties, E = 115 GPa; and zirconia (Yz) - stiffest material, E = 210 GPa). The surfaces were treated and bonded with resin cement (disc-disc set-up). Fatigue testing followed a step-stress approach (initial maximum load = 200 N for 5000 cycles, incremental step load = 200 N for 10,000 cycles/step). The fatigue failure load and number of cycles until failure were recorded and statistically analyzed. Fractographic and finite element (FEA) analyzes were conducted as well. TZ ceramic depicted higher fatigue failure load, number of cycles until failure, and survival probabilities than LD, irrespective of the substrate. Moreover, TZ and LD presented better fatigue behaviors when bonded to substrates Ti and Yz in comparison to FRC. FEA revealed lower tensile stresses at restorative material when bonded to stiffer substrates. Fractography showed that the fracture origin started at bottom surface of restorative material (except for TZ bonded to Yz, in which crack initiated at load contact point). Translucent zirconia polycrystals present superior mechanical behavior than lithium disilicate glass-ceramic. The substrate type influences the mechanical performance of monolithic dental ceramics (stiffer substrates lead to better fatigue behavior).

To evaluate the influence of resin cement on the color stability of lithium disilicate and zirconia restorations immersed in coffee after aging. Eighty maxillary premolars were classified into eight groups (n = 10) based on restorative material type (lithium disilicate or zirconia), resin cement type (G-CEM LinkForce; GC Corporation or Panavia SA Cement Plus Automix; Kuraray Noritake Dental), and preheating temperature (25°C or 54°C). Following tooth preparation, each restoration was bonded to its corresponding substrate. Using a reflectance spectrophotometer, Commission Internationale de l'Éclairage (CIE) tristimulus values were detected and calculated (D65 standard illumination, 10-degree observer angle). All specimens were aged (240,000 load cycles followed by 10,000 thermal cycles), then immersed in coffee (18 h). Following that, the second measurements of the color coordinates were determined. The total color differences were measured, and the data were statistically analyzed (α = 0.05). The temperature had a significant effect on ΔL΄ (P < 0.001), ΔC΄ (P < 0.001), and ΔH΄ (P < 0.001). The lithium disilicate restorations were more color stable than the zirconia restorations. Also, there was a significant difference (P = 0.047) between the LinkForce (2.28 ± 0.48) and Panavia SA (2.15 ± 0.46) cement. The restorations cemented at a temperature of 54°C (1.76 ± 0.11) showed significant color differences (P < 0.001) compared with those cemented at a temperature of 25°C (2.67 ± 0.15). A three-way analysis of variance (ANOVA) test revealed that the interaction between the ceramic material, cement type, and temperature had no statistically significant effect (P = 0.611) on the color stability of the ceramic restorations. Cement type has a significant effect on the color stability of lithium disilicate and zirconia restorations. Cement at a temperature of up to 54°C enhances the color stability of lithium disilicate and zirconia restorations.

Bimaxillary implant-supported restorations for edentulous patients must include a comprehensive diagnosis, treatment plan, and careful selection of the restorative materials. The present clinical report described a completely edentulous patient rehabilitated with a zirconia framework with a facial ceramic veneer on the maxillary arch and a modified polyetheretherketone (PEEK) framework with gingival composite resin and cemented lithium disilicate crowns on the mandibular arch. The rationale for this combination of restorative materials is reviewed.

To determine the survival and success rate of CAD/CAM-fabricated monolithic lithium-disilicate crowns supported by zirconia oral implants after 3 years. Twenty-four patients in need of a single tooth replacement received a zirconia implant and were finally restored with 24 single crowns (SCs) ground out of pre-crystallized lithium-disilicate blanks. The restorations were adhesively cemented and evaluated using modified United States Public Health Service (USPHS) criteria. In case of clinically relevant defects that could be repaired to an acceptable level, SCs were regarded as surviving. Restorations with minor chippings, a small-area roughness (ø <2 mm), slightly soundable marginal gaps, minimal under-/overcontours, and tolerable color deviations (<1 Vitashade) were regarded as success. The Kaplan-Meier method and log-rank tests were used for the success/survival analyses and the calculation of potential group differences (gender, location, jaw). Additionally, several patient-reported outcome measures (PROMs) were evaluated. Twenty-three patients were seen 3 years after implant placement. No SC had to be replaced, resulting in 100% survival. No chippings were observed. As one SC showed a major occlusal roughness, the Kaplan-Meier success rate after a mean observation period of 31 months was 95.7%. No group differences could be calculated. Compared with the pre-treatment surveys, the further PROMs showed a permanently improved perception of function, esthetics, sense, and speech. Monolithic lithium-disilicate SCs supported by zirconia implants showed promising survival and success rates after an observation period of 3 years. It remains to be seen whether the further observation period confirms this positive results.

To evaluate the bending moments and failure modes of zirconia meso-abutments bonded to titanium bases restored with different monolithic all-ceramic crowns after aging, and to compare them to titanium abutments restored with all-ceramic crowns. Forty-eight internal conical connection implants (Conelog, Camlog 4.3 mm diameter) were restored with four different computer-aided design/computed-aided manufacturing (CAD/CAM) abutment-crown combinations (n = 12). Thirty-six customized zirconia meso-abutments were bonded to titanium bases (Conelog Titanium Base CAD/CAM crown, Camlog) and divided into three groups according to the different crown materials: (T1) monolithic lithium-disilicate (e-max CAD, Ivoclar), (T2) monolithic PICN (polymer-infiltrated ceramic network [Enamic, Vita]), and (T3) monolithic zirconia (Lava Plus, 3M ESPE). Twelve titanium customized abutments restored with monolithic lithium-disilicate (e-max CAD, Ivoclar) crowns served as the control group (C). The crowns were equal maxillary central incisors and were adhesively bonded with a resin-based cement (Panavia 21, Kuraray). All samples were embedded in acrylic holders. After aging (1,200,000 cycles, 49 N, 1.67 Hz, 5°C to 50°C, 120 seconds), static load was applied until failure. Bending moments were calculated for comparison of the groups. Data were statistically treated with one-way analysis of variance (ANOVA) followed by Tukey post hoc test (P < .05). Failure modes were analyzed descriptively. The means of the bending moments were 356.4 ± 20.8 Ncm (T1), 357.7 ± 26.3 Ncm (T2), 385.5 ± 21.2 Ncm (T3), and 358.8 ± 25.3 Ncm (C). Group T3 revealed significantly higher mean bending moments than the other groups (P < .05). No differences were found between zirconia meso-abutments supported by titanium bases and customized titanium abutments when lithium-disilicate crowns were used (P > .05). No failures were identified during and after aging. After static load, failures occurred due to fracture of the abutment in the internal connection in all the groups. Zirconia meso-abutments bonded to titanium bases showed similar mechanical stability compared with customized titanium abutments. Regarding the crown material, all three tested ceramics (lithium-disilicate, PICN, and zirconia) revealed very good stability when used in the monolithic state.

To evaluate the fracture resistance of all-ceramic crowns cemented on titanium and zirconia implant abutments. Customized implant abutments for maxillary right central incisors made of titanium (Ti) and zirconia (Zr) (n=60, n=30 per group) were fabricated for an internal connection implant system. All-ceramic crowns were fabricated for their corresponding implant abutments using the following systems (n=10 per group): (1) monolithic computer-aided design/computer-assisted manufacture (CAD/CAM) lithium disilicate (MLD); (2) pressed lithium disilicate (PLD); (3) yttrium stabilized tetragonal zirconia polycrystal (YTZP). The frameworks of both PLD and YTZP systems were manually veneered with a fluorapatite-based ceramic. The crowns were adhesively cemented to their implant abutments and loaded to fracture in a universal testing machine (0.5 mm/minute). Data were analyzed using two-way analysis of variance (ANOVA) and Tukey's test (α=0.05). Both the abutment material (P=.0001) and the ceramic crown system (P=.028) significantly affected the results. Interaction terms were not significant (P=.598). Ti-MLD (558.5±35 N) showed the highest mean fracture resistance among all abutment-crown combinations (340.3±62-495.9±53 N) (P<.05). Both MLD and veneered ceramic systems in combination with Ti abutments (558.5±35-495.9±53 N) presented significantly higher values than with Zr abutments (392.9±55-340.3±62 N) (P<.05). MLD crown system showed significantly higher mean fracture resistance compared to manually veneered ones on both Ti and Zr abutments (P<.05). While Ti-MLD and Ti-PLD abutment-crown combinations failed only in the crowns without abutment fractures, Zr-YTZP combination failed exclusively in the abutment without crown fracture. Zr-MLD and Zr-PLD failed predominantly in both the abutment and the crown. Ti-YTZP showed only implant neck distortion. The highest fracture resistance was obtained with titanium abutments restored with MLD crowns, but the failure type was more favorable with Ti-YTZP combination.

To compare the fracture resistance between bilayered zirconia/ fluorapatite and monolithic lithium disilicate heat-pressed crowns and characterize the mode of fracture failure. Thirty crown samples were sequentially fitted on a mandibular right first molar metal replica of an ivory prepared molar tooth. The crown specimens were divided in three groups (A, B, and C; n = 10 for each group). Group A consisted of bilayered zirconia/fluorhapatite pressed-over crowns with standard design crown copings (0.7 mm uniform thickness), Group B of bilayered zirconia/fluorhapatite with anatomical design crown copings, and Group C of lithium disilicate monolithic crowns. The samples were then dynamically loaded under water for 100,000 cycles with a profile of 250 N maximum load at 1,000 N/s rate and 2.0 Hz frequency. Loading was performed with a steel ball (5 mm in diameter) coming into contact with the test crown, loading to maximum, holding for 0.2 s, unloading and lifting off 0.5 mm. The samples were then fractured under static loading, in order to determine the ultimate crown strength. Analysis of the recorded fracture load values was carried out with one-way analysis of variance (ANOVA) followed by Tukey tests. Fractured specimens were examined by stereomicroscopy and scanning electron microscopy. The fracture loads measured were (N, means and standard deviations): Group A: 561.87 (72.63), Group B: 1,014.16 (70.18) and Group C: 1,360.63 (77.95). All mean differences were statistically significant (P < 0.001). Catastrophic fractures occurred in Group C, whereas mainly veneer fractures were observed in Groups A and B. In the present study, the heat-pressed monolithic lithium-disilicate crowns showed more fracture resistance than zirconia/fluorapatite pressed-over crowns. Within the bilayered groups, the anatomical zirconia coping design presented increased ceramic fracture resistance.

The authors analyzed the effect of fatigue on the survival rate and fracture load of monolithic and bi-layer CAD/CAM lithium-disilicate posterior three-unit fixed dental prostheses (FDPs) in comparison to the metal-ceramic gold standard. The authors divided 96 human premolars and molars into three equal groups. Lithium-disilicate ceramic (IPS-e.max-CAD) was milled with the CEREC-3-system in full-anatomic FDP dimensions (monolithic: M-LiCAD) or as framework (Bi-layer: BL-LiCAD) with subsequent hand-layer veneering. Metal-ceramic FDPs (MC) served as control. Single-load-to-failure tests were performed before and after mouth-motion fatigue. No fracture failures occurred during fatigue. Median fracture loads in [N], before and after fatigue were, respectively, as follows: M-LiCAD, 1,298/1,900; BL-LiCAD, 817/699; MC, 1,966/1,818. M-LiCAD and MC FPDs revealed comparable fracture loads and were both significantly higher than BL-LiCAD. M-LiCAD and BL-LiCAD both failed from core/veneer bulk fracture within the connector area. MC failures were limited to ceramic veneer fractures exposing the metal core. Fatigue had no significant effect on any group. Posterior monolithic CAD/CAM fabricated lithium-disilicate FPDs were shown to be fracture resistant with failure load results comparable to the metal-ceramic gold standard. Clinical investigations are needed to confirm these promising laboratory results. Monolithic CAD/CAM fabricated lithium-disilicate FDPs appeared to be a reliable treatment alternative for the posterior load-bearing area, whereas FDPs in bi-layer configuration were susceptible to low load fracture failure.

The aim of this study was to evaluate and compare the fracture resistance of inlay preparations restored with indirect lab composite, conventional and translucent monolithic zirconia-based ceramics. Fifty freshly extracted human maxillary premolars were selected for the study. Standardized inlay cavities were prepared and restored with indirect lab composite, conventional monolithic zirconia-based ceramic and translucent monolithic zirconia-based ceramic. After restoration each sample was subjected to axial compressive load with Universal testing machine. The force required to induce fracture was recorded in Newton (N). The data were analyzed using the one-way ANOVA test and Results revealed that fracture resistance of prepared inlay cavities restored with conventional monolithic zirconia-based ceramics was found to be best followed by other groups. Group I > Group IV > Group V > Group III > Group II. The fracture resistance of conventional monolithic zirconia-based ceramic inlays and translucent monolithic zirconia-based ceramic inlays were comparable with intact teeth but, indirect lab composite inlays showed lower fracture resistance than all.

To investigate the fracture resistance of monolithic CAD-CAM all-ceramic surveyed crowns with two different occlusal rest seat designs. Two maxillary first premolar were prepared for all-ceramic surveyed crowns with wide (2/3 The mean ± standard deviation of maximum failure force values varied from 3476.10 ± 285.97 N for the narrow ORS subgroup of group ZIPS to 687.89 ± 167.63 N for the wide ORS subgroup of group CR. The mean ± standard deviation of maximum force was 1075 ± 77.0 N for group CR, 1309.3 ± 283.9 N for group LDS, 3476.1 ± 285.97 N for group ZIPS, and 2666.7 ± 228.21 N for group ZLHT, with narrow occlusal rest seat design. The results of the intergroup comparison showed significant differences in fracture strength with various material groups and occlusal rest seat designs ( The zirconia-based all-ceramic surveyed crowns fractured at more than double the load of Lithium disilicate based crowns. The crowns with narrow base occlusal rest seat design had statistically significantly higher fracture resistance than surveyed crowns with wide occlusal rest seat design. The use of narrow occlusal rest seat design in CAD-CAM all ceramic surveyed crowns provides higher fracture resistance, and therefore narrow occlusal rest design can be used for providing esthetics with high strength.

To compare the effects of different thicknesses of ceramic veneering on the light transmission of various monolithic zirconia and lithium disilicate materials used in esthetic restorations. Zirconia (i.e., Katana UT, Katana HT, Prozir Diamond, Prozir HT, and Zenostar MO) and lithium disilicate specimens (i.e., Emax HT and Emax MO) were prepared at thicknesses of 0.5 mm, 0.8 mm, and 1.2 mm. Additionally, 0.8 mm-thick specimens and 0.3 mm-thick ceramic veneer were prepared for veneering groups. The total transmittance of light values were measured using a spectrophotometer. The light transmission values were analyzed using the Kruskal-Wallis and the post-hoc Dunnett tests (α= 0.05). The Emax HT group defined significant differences from all groups (P< 0.05) at all thicknesses. The mean total transmittance of light ranged from 5.53% to 19.55%. There was no significant difference between the Katana UT and Prozir Diamond groups at the 0.5 mm, 0.8 mm, and 1.2 mm thicknesses (P> 0.05). The results of this study showed no significant effects of veneering ceramic on the light transmittance of the specimens at a thickness of 0.8 mm. Novel monolithic zirconia materials may be preferred over porcelain veneering in 0.8 mm-thick restorations, as the esthetic appearance of the restorations would not change.

To compare three different compositions of Yttria-Tetragonal Zirconia Polycrystal (Y-TZP) ceramic and a lithium disilicate ceramic in terms of flexural strength and translucency. Three zirconia materials of different composition and translucency, Aadva ST [ST], Aadva EI [EI] and Aadva NT [NT](GC Tech, Leuven, Belgium) were cut with a slow speed diamond saw into beams and tabs in order to obtain, after sintering, dimensions of 1.2×4.0×15.0mm and 15.0×15.0×1.0mm respectively. Blocks of IPS e.max CAD LT were cut and crystallized in the same shapes and dimensions and used as a reference group [LD]. Beams (n=15) were tested in a universal testing machine for three-point bending strength. Critical fracture load was recorded in N, flexural strength (σ in MPa), Weibull modulus (m) and Weibull characteristic strength (σ Differences in translucency, flexural strength and grain size were found to be statistically significant. CR increased and flexural strength decreased in the following order ST(σ 1215±190MPa, CR 0.74±0.01)>EI(σ 983±182MPa, CR 0.69±0.01)>NT(σ 539±66MPa, CR 0.65±0.01)>LD (σ 377±39Mpa, CR 0.56±0.02). The average grain size was different for the three zirconia samples with NT(558±38nm)>ST(445±34nm)>EI(284±11nm). The zirconia composition heavily influenced both the flexural strength and the translucency. Different percentages of Yittria and Alumina result in new materials with intermediate properties in between the conventional zirconia and lithium disilicate. Clinical indications for Zirconia Aadva NT should be limited up to three-unit span bridges.

Evidence comparing the survival of zirconia crowns with metal-ceramic crowns is sparse. Knowledge of their survival and a comparison of their clinical outcomes would improve clinical decision making. The purpose of this university-based study was to compare the survival, failures, biological and technical complications encountered with zirconia and metal-ceramic crowns restored and followed up over a similar period. This retrospective chart review consisted of 403 patients treated at the University of Toronto, Faculty of Dentistry, predoctoral dental clinic in whom zirconia (n=209) and metal-ceramic (n=306) crowns were inserted between September 2015 and July 2016 and followed for up to 7 years. Outcome measures included failure, causes for failure, and complications associated with survival. Inferential statistical analysis included the chi-squared test, t test, Mann-Whitney test, Bonferroni-adjusted z-test, Kaplan-Meier survival test, and logistic regression to examine differences between crown types and explore crown failures (α=.05). The mean follow-up period was 3.00 years (median 2.58 years). Forty-one (8.0%) crowns had no follow-up, with no difference in follow-up between crown type: metal-ceramic n=23(7.5%), zirconia n=18(8.6%), χ²(1)=0.20, P=.652). Excluding those with no follow-up, the follow-up time between metal-ceramic (mean=3.07, median=2.58) and zirconia (mean=3.54, median=3.32) crowns was statistically similar (P=.052). There were 62 anterior crowns (12.0%) and 453 posterior crowns (88.0%), χ²(1)=22.40, P<.001, with no difference between groups. Overall, 44 crowns (8.5%) failed, 30 (9.8%) metal-ceramic and 14 (6.7%) zirconia, with no statistical difference in proportion of failed crowns between groups (χ²(1)=1.53, P=.216). There were 35 crowns with biological failures (6.8%), 26 (8.5%) in the metal-ceramic and 9 (4.4%) in the zirconia group, with no statistical difference between groups (χ²(1)=3.33, P=.068). Nine crowns had technical failures (1.7%), 4 (1.4%) in the metal-ceramic group and 5 (2.5%) in the zirconia group, with no statistical difference between groups (χ²(1)=0.73, P=.394). Biological (79.5%) rather than technical complications were found to be the most frequent cause of failure, goodness-of-fit χ²(1)=15.36, P<.001. Tooth fracture (50.0%) specifically was found to be the most frequent cause of failure, χ²(3)=21.27, P<.001. The total number of crowns that survived was 471 (91.5%); 276 (90.1%) were metal-ceramic and 195(93.3%) zirconia. The survival time (years) for metal-ceramic was mean=6.26, 95% CI [6.01-6.51] and for zirconia crowns mean=6.54, 95% CI [6.31-6.77]. Of the crowns that survived, 370 (78.6%) had no clinical complications, and 101 (21.4%) crowns demonstrated similar clinical complications, with no statistical differences between groups. Within the study follow-up time, the survival of monolithic zirconia and metal-ceramic crowns was 91.5%, with similar clinical complications between groups. Biological complications, especially tooth fracture, were a significantly more frequent complication with both types of crowns.

The purpose of this study was to assess the pull-out bond strength (PBS) of endodontically treated anterior teeth that had been restored with monolithic zirconia endocrowns using different extension depths (EDs) and post-and-core crowns after chewing simulation. Thirty-six maxillary central teeth were used (n = 12). Group I: Glass fiber post-and-core crown, Group II: Endocrown with 3-mm EDs, Group III: Endocrown with 5-mm EDs. Restorations were fabricated from monolithic zirconia blocks using a CAM (computer-aided manufacturing) device. For cementation, conventional resin luting agent (Multilink N) was used. All samples were aged with a chewing simulator and PBS tests were conducted at a speed of 1 mm/min using an electromechanical servo universal testing machine. The values were recorded in MPa by dividing the failure load by the bonding area. One-way ANOVA and the post-hoc Tukey test were used for statistical analysis (P = 0.05). Group III demonstrated significantly greater PBS values than Groups I and II (P = 0.001). No significant difference was found between Groups I and II (P = 0.072). Increasing the ED of an endocrown influences the PBS of endodontically treated anterior teeth restored with monolithic zirconia endocrowns.

The wear of monolithic zirconia against enamel has been widely studied, but how zirconia affects different opposing restorative materials is not clear. The purpose of this in vitro study was to investigate the depth of wear and volumetric loss of different restorative materials opposed by monolithic zirconia. Sixty-six Ø10×3-mm specimens (n=11) were fabricated from monolithic zirconia, zirconia reinforced ceramic, lithium disilicate ceramic, feldspathic ceramic, ORMOCER, and ceramic optimized polymer. A 2-body pin-on-disk wear test was performed by using monolithic zirconia pins. The specimens were scanned with a noncontact profilometer after the tests. The scan parameters were a frame size area of 1.5×1.5 mm, frequency of 400 Hz, and scan sensitivity of 2 μm. After the evaluation of depth and volume loss, the specimens were analyzed with a scanning electron microscope. The Kruskal-Wallis test was used to analyze the differences in wear values across the specimen groups, and pairwise comparison tests were performed with a post hoc test (α=.05). Maximum depth of wear was 257.55 ±18.88 μm for lithium disilicate ceramic, 295.36 ±14.46 μm for zirconia reinforced ceramic, 421.82 ±214.49 μm for ORMOCER, 333.73 ±79.09 μm for ceramic optimized polymer, 146.27 ±22.86 μm for feldspathic ceramic, and 41.55 ±5.04 μm for monolithic zirconia. The depth of wear was not significantly different among lithium disilicate, zirconia-reinforced ceramic, ORMOCER, and ceramic optimized polymer (P<.05). However, the depth of wear of monolithic zirconia and feldspathic ceramic was less than that of other materials (P<.001). Volume loss of lithium disilicate was 1.68 ±0.25 mm The tested ceramic-based materials had favorable wear resistance compared with the tested composite resin-based ones. However, the ceramics tended to crack formation than the composite resins.

To evaluate the marginal adaptation and internal space of crowns produced by 4 CAD/CAM systems using microcomputed tomography (μCT) and replica technique (RT). Monolithic lithium disilicate crowns were milled (Ceramill, Cerec, EDG, and Zirkonzahn) (n = 10). The cement film obtained with low viscosity silicone was scanned by the μCT system and captured by a stereomicroscope, according to RT. Two-way ANOVA followed by Tukey's test were used for statistical analysis (α = 0.05). A uniformity index (UI) was idealized to describe the distribution of crowns' internal space and submitted to the Kruskal-Wallis and Tukey's test (α = 0.05). The correlation between μCT and RT was performed by Pearson's Correlation Coeficient (α = 0.05). Marginal adaptation and internal space were statistically significant different between the experimental groups for the μCT and RT (p < 0.05). The medians of the 4 systems tested were within clinically acceptable range and the mean (± SD) highest marginal discrepancy was recorded in the Ceramill group at 133.0 ± 71.5 μm (μCT) and 90.6 ± 38.5 μm (RT). For internal fit, the UI disclosed a better distribution of the internal space for the Zirkonzahn group (p < 0.001). There was a strong correlation between the methods (p = 0.01 and r = 0.69). Because of the variability of the CAD/CAM systems available, evaluating their accuracy is of clinical interest. The 4 systems are capable to produce restorations adaptated within clinically appropriate levels. The μCT and RT are efficient adaptation methodologies.

The aim of this randomized controlled trial was to see if the minimally invasive approach (reduced restoration thickness) would result in good clinical success of monolithic ceramic crowns compared to conventional layered all-ceramic crowns, and thus be an alternative to conventional tooth preparation. The ceramic that was investigated was IPS e.max lithium-disilicate ceramic produced using two different processing methods. A comparison was made between monolithic crowns with reduced thickness and standard layered crowns. Fifty-two patients, who had undergone endodontic treatment on either a premolar or molar, were randomly assigned into two groups. The teeth intended for layered crowns underwent to a 2 mm occlusal reduction with a 1 mm rounded shoulder, whereas the teeth intended for monolithic crowns underwent to a 1 mm reduction in the occlusal area with a 0.6 mm rounded shoulder. The clinical success was evaluated in eight categories using modified United States Public Health Service (USPHS) criteria. The observation period was 36 months, with control appointments every 6 months. There was no significant difference in clinical success between monolithic and conventional layered crowns after 3 years. One monolithic crown fractured while all other crowns were intact and the survival rate was 96%. All layered crowns were intact and the survival rate was 100%. The results of this study indicate that the minimally invasive approach can be a good alternative to conventional tooth preparation. IPS e.max lithium-disilicate ceramic demonstrated an exceptional three-year survival rate independently of the thickness of the material.

The purpose of this study is to correct the movement errors that may occur because of the patients' movement during the CT scanning and thus, to obtain more precise CT images, additionally to investigate the possible use of Parallel Beam CT in the dental treatment. An extracted human tooth was scanned with PBCT and the possible movement errors that patients may cause during the CT scan were intentionally assigned. The maximum width of errors was designed to reach 0.1 mm. The trajectory of the fixed point was traced in the sinogram that includes the fixed point. The part deviated from the sinusoidal curve was modified using the Virtual Alignment Method. The quality of reconstructed image was remarkably degraded when the movement errors were given. A radiopaque part inside the tooth was used as a fixed point. The errors were corrected by shifting the fixed point to the center of sinogram and this relocation of fixed point did not cause any distortion of image or change of size. The movement errors were corrected with the fixed point inside the tooth. The more precise CT images obtained through this method are expected to be of extensive application in the area of dental treatment using CAD/CAM.

Dislocations are line defects in crystalline solids and often exert a significant influence on the mechanical properties of metals. Recently, there has been a growing interest in using dislocations in ceramics to enhance materials performance. However, dislocation engineering has frequently been deemed uncommon in ceramics owing to the brittle nature of ceramics. Contradicting this conventional view, various approaches have been used to introduce dislocations into ceramic materials without crack formation, thereby paving the way for controlled ceramics performance. However, the influence of dislocations on functional properties is equally complicated owing to the intricate structure of ceramic materials. Furthermore, despite numerous experiments and simulations investigating dislocation-controlled properties in ceramics, comprehensive reviews summarizing the effects of dislocations on ceramics are still lacking. This review focuses on some representative dislocation-controlled properties of ceramic materials, including mechanical and some key functional properties, such as transport, ferroelectricity, thermal conductivity, and superconducting properties. A brief integration of dislocations in ceramic is anticipated to offer new insights for the advancement of dislocation engineering across various disciplines.

Lithium disilicate glasses and glass-ceramics are good potential candidates for biomedical applications and solid-state batteries, and serve as models of nucleation and crystal growth. Moreover, these glasses exhibit a phase separation that influences their nucleation and crystallization behavior. The atomistic mechanisms of the phase separation and their pressure dependence are unclear so far. Here, we used molecular dynamics simulations supported by experiments to assess the spatial heterogeneity of lithium disilicate glasses prepared under pressure. We show that the glass heterogeneity decreases with increasing the cooling pressure and almost disappears at pressures around 30 GPa. The origin of the heterogeneity is due to the attraction between Li cations to form clustering channels, which decreases with pressure. Through our results, we hope to provide valuable insights and guidance for making glass-ceramics with controlled crystallization.

Solid solutions of SiO2 and B2O3 in Li2O 2SiO2 are synthesized and characterized for the first time. Their structure and crystallization mechanisms are investigated employing a combination of simulations at the density functional theory level and experiments on the crystallization of SiO2 and B2O3 doped lithium disilicate glasses. The remarkable agreement of calculated and experimentally determined cell parameters reveals the preferential, kinetically controlled incorporation of [SiO4] and [BO4] at the Li+ lattice sites of the Li2O 2SiO2 crystal structure. While the addition of SiO2 increases the glass viscosity resulting in lower crystal growth velocities, glasses containing B2O3 show a reduction of both viscosities and crystal growth velocities. These observations could be rationalized by a change of the chemical composition of the glass matrix surrounding the precipitated crystal phase during the course of crystallization, which leads to a deceleration of the attachment of building units required for further crystal growth at the liquid-crystal interface.

Zirconia is well-known for plenty of important morphologys with Zr coordination varying from sixfold in the octagonal phase to eightfold in the cubic or tetragonal phase. The development of empirical potentials to describe these zirconia morphologys is an important issue but a long-standing challenge, which becomes a bottleneck for the theoretical investigation of large zirconia structures. In contrast to the standard core-shell model, we develop a new potential for zirconia through the combination of long-range Coulomb interaction and bond order Tersoff model. The bond order characteristic of the Tersoff potential enables it to be well suited for the description of these zirconia morphologys with different coordination numbers. In particular, the complex monoclinic phase with two inequivalent oxygens, that is difficult to be described by most existing empirical potentials, can be well captured by this newly developed potential. It is shown that this potential can provide reasonable predictions for most static and dynamic properties of various zirconia morphologys. Besides its clear physical essence, this potential is at least one order faster than core-shell based potentials in the molecule dynamics simulation, as it discards the concept of the ultralight shell that demands for an extremely small time step. We also provide potential scripts for the widely used packages GULP and LAMMPS.