数字化技术在全口义齿组织面倒凹处理中的应用

The present study explains the clinically observed enhanced retention and lower traumatic ulcer-frequency in CAD/CAM dentures.

This study evaluated the effects of the differences in the printing directions of stereolithography (SLA) three-dimensional (3D)-printed dentures on accuracy (trueness and precision). The maxillary denture was designed using computer-aided design (CAD) software with an STL file (master data) as the output. Three different printing directions (0°, 45°, and 90°) were used. Photopolymer resin was 3D-printed (n = 6/group). After scanning all dentures, the scanning data were saved/output as STL files (experimental data). For trueness, the experimental data were superimposed on the master data sets. For precision, the experimental data were selected from six dentures with three different printing directions and superimposed. The root mean square error (RMSE) and color map data were obtained using a deviation analysis. The averages of the RMSE values of trueness and precision at 0°, 45°, and 90° were statistically compared. The RMSE of trueness and precision were lowest at 45°, followed by 90°; the highest occurred at 0°. The RMSE of trueness and precision were significantly different among all printing directions (<i>p</i> < 0.05). The highest trueness and precision and the most favorable surface adaptation occurred when the printing direction was 45°; therefore, this may be the most effective direction for manufacturing SLA 3D-printed dentures.

The overall accuracy of the denture base is higher in milling and RP method than the injection molding method. The degree of fine reproducibility is higher in the injection molding method than the milling or RP method.

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Purpose The trueness and fitting accuracy of complete dentures (CDs) manufactured digitally from wax dentures have not been investigated yet. This study evaluated the trueness and fitting accuracy of maxillary CDs manufactured using computer-aided design technology.Methods CD bases were manufactured from fully edentulous maxillary casts using a milling machine and three three-dimensional (3D) printers (two stereolithography apparatus (SLA) and one digital light processing (DLP)). 3D printing was performed using an SLA printer with eight build support angles (0° to 315°). As a control, a CD base was conventionally fabricated using a heat-polymerized PMMA resin. After the tissue surfaces of the casts and the cameo surfaces of all the CD bases were scanned, their STL data were superimposed with a best-fit alignment. The deviations of all the CD bases were evaluated using data-matching software.Results The milled CD bases showed higher trueness and fitting accuracy compared with the 3D-printed and conventional bases. SLA showed a higher fitting accuracy than DLP. The best support angles for the fitting accuracy were 45° and 225°. The fitting accuracy of the SLA 3D-printed CD bases with an angle of 45° was comparable to or slightly higher than that of conventionally fabricated bases.Conclusions The milled CD bases showed an excellent fitting accuracy. The SLA-printed CDs demonstrated a clinically acceptable fitting accuracy.

Based on multisource data from spiral CT and the intraoral scanner, 3D digital casts of maxillary defects were generated using the registration technique. These casts were consistent with conventional stone casts in terms of accuracy and were suitable for clinical use.

In this study, the combination of intraoral and face scans allowed to successfully restore fully edentulous patients with maxillary overdentures supported by 4 implants and a CAD/CAM PEEK bar. Further studies are needed to confirm these outcomes.

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The CI, SI, and DI methods were effective in making impressions of the supporting areas in edentulous patients. The SI method showed clinically applicability.

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SLM is a promising technique for the fabrication of RPD frameworks in routine clinical practice.

IOS is a fast, safe, and feasible procedure for neonates, small children, and infants with craniofacial malformations. One special challenge for both technician and user was identified in patients with CLP, though implementing this new approach of digital impression taking was otherwise found to be highly successful in everyday clinical routine.

The objective was to compare the adaptation between the major connectors of removable partial dentures derived from intraoral digital impressions and extraoral digital impressions. Twenty-four volunteers were enrolled. Each volunteer received an intraoral digital impression and one extraoral digital impression digitized from conventional gypsum impression. A software was used to create the major connectors on digital impression datasets. After all the virtual major connectors designed from Group intraoral digital impressions (Group I) and Group extraoral digital impressions (Group E) were directly fabricated by 3D printing technique, the adaptation of the final major connectors in volunteers' mouths were measured. The adaptation ranged from 159.87 to 577.99 μm in Group I while from 120.83 to 536.17 μm in Group E. The adaptation of major connectors in Group I were found better at the midline palatine suture while the adaptation of major connectors in Group E were found better at the two sides of the palatal vault. In both groups, the highest accuracy in adaptation was revealed at the anterior margin of the major connectors. It is feasible to manufacture the major connectors by digital impression and 3D printing technique. Both the adaptation of the two kinds of digital impressions were clinical acceptable.

Maxillofacial surgery patients may develop postoperative complications such as trismus and pain. In these cases, the combination of digital technology and conventional techniques provide an accurate prosthetic restoration.

Although digital impression using an intraoral scanner (IOS) has been applied for removable partial denture (RPD) fabrication, it is still unclear how the morphology of a residual ridge recorded by digital impression would differ from that recorded by conventional impression. This in vivo study investigated the morphological difference in the recorded residual ridge between digital and conventional impressions. Vertical and horizontal displacements (VD and HD) in residual ridges recorded by digital and conventional impressions were assessed in 22 participants (15 female; mean age 78.2 years) based on the morphology of the tissue surface of in-use RPD. Additionally, the mucosal thickness of the residual ridge was recorded using an ultrasound diagnostic device. VD and HD were compared using the Wilcoxon signed-rank test, and the correlation of mucosal thickness with VD and HD was analyzed using Spearman's <i>ρ</i>. The VD of digital impression was significantly greater than that of a conventional impression (<i>p</i> = 0.031), while no significant difference was found in HD (<i>p</i> = 0.322). Meanwhile, the mucosal thickness showed no significant correlation with the recorded morphology of the residual ridge, regardless of the impression techniques. It was concluded that the digital impression would result in a greater displacement in the height of the residual ridge from the morphology of in-use RPD than the conventional impression.

This study explored a method for CAD of removable partial denture (RPD) framework, which contributes to the development of a specialized software system used in restorative dentistry. Point cloud data of a mandibular partially edentulous cast was captured by an optical scanning system with projective grating and high-resolution digital camera. The 3D model of the cast was rebuilt by a CAD software system from the 3D cloud points. Based on the principle of clinical design, the digital survey line and inserting path were determined automaticly. The tissue surfaces and polishing surfaces of every component of RPD were built also by the CAD software. Furthermore, the characteristic structures of the framework including the lingual bar, the internal and external finish lines, the tissue stop were fabricated on the base of the rebuilt model. 3D surface model of the RPD framework was created at last. In this study, geometric model of the RPD framework was fabricated successfully, which took on good fitting, high visibility and easy to modify, and the data converted to STL format that could be read by any other CAD/CAM software system was in preparation for subsequent computer aided manufacture (CAM) of RPD framework.

To date, CAD/CAM technology has made no noteworthy inroads into removable dentures. We want to present a new area of application for this in our study. Models of the maxilla and edentulous mandible were 3D scanned. The software detects and automatically reconstructs the reference structures that are anatomically important for the set-up of artificial teeth, such as the alveolar ridge centerlines and the interalveolar relations between the alveolar ridges. In a further step, the occlusal plane is semiautomatically defined and the front dental arch is designed. After these design features have been determined, artificial teeth are selected from a database and set up automatically. The dental technician can assess the esthetics and function of the suggested dental set-up on the computer screen and make slight corrections if necessary. Summarizing: The interplay of hardware and software components within on integrated solution including conversion of the "virtual" into a real positioning of prosthetic teeth is presented.

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Light-polymerizing reline materials offer improved chairside workability compared to conventional auto-polymerizing reline materials, addressing the partial denture (RPD) incompatibility caused by residual ridge resorption owing to long-term use. This study evaluates the fitting accuracy of relined materials by combining conventional fitting tests with three-dimensional (3D) measurements for detailed analysis. Light-polymerizing reline material (HikariLiner^®, Tokuyama, Tokyo, Japan, LP) and auto-polymerizing material (Rebase III^®, Tokuyama, AP) were used. The gaps formed between the relined denture base and the simplified edentulous model were evaluated. The displacement and deviation of the experimentally relined RPDs on the partially edentulous models were analyzed using 3D data superimposition. In the edentulous model, the gaps at all measurement points were significantly smaller for the AP than in the LP. Moreover, the alveolar ridge crest gap was significantly larger than that at other sites. In the partial denture model, the RMS values at the residual ridge crest were significantly lower for the AP. The evaluation method using 3D scanning and comparison was suitable for a detailed fit analysis. Further improvements in the scanning accuracy may enhance future assessments. Therefore, the evaluation method using 3D scanning and comparison was suitable for effectively analyzing the fit of relines, necessitating further accuracy improvements.

A new trial method for complete dentures using rapid prototyping (RP) was compared with the conventional method. Wax dentures were fabricated for 10 edentulous patients. Cone-beam CT was used to scan the wax dentures. Using 3D computer-aided design software, seven 3D denture images with different artificial teeth arrangements were made and seven trial dentures per patient were fabricated accordingly. Two prosthodontists performed a denture try-in for one patient using both conventional and RP methods. The prosthodontists and patients rated satisfaction for both methods using a visual analogue scale. Satisfaction ratings with both conventional and RP methods were compared using the Wilcoxon signed-rank test. Regarding prosthodontist's ratings, esthetics and stability were rated significantly higher with the conventional method than with the RP method, whereas chair time was rated significantly longer with the RP method than with the conventional method. Although further improvements are needed, the trial method applying RP seems promising.

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In computer-guided implant surgery, an accurate 3-dimensional (3D) image matching of the hard and soft tissues obtained by cone-beam computerized tomography (CBCT) and optical surface scanners is a prerequisite for prosthetic treatment planning, implant positioning, and surgical guide fabrication.1,2 Identical anatomic features that are clearly discernible in the optical and radiographic scan data are used as references to match the acquired images.3,4 Natural teeth are commonly selected as fiducial landmarks for image matching in partially edentulous cases.3 In completely edentulous cases, because of the absence of natural teeth, special techniques are required to match the optical and radiographic data.4,5The double scan protocol has been considered the most common method for image matching in completely edentulous cases.6,7 The early developed technique consists of 2 radiographic scans, one of the patient wearing the scan prosthesis and the other of the prosthesis alone.8 The implant-planning software converts the radiographic scan files into 3D surface mesh images and merges the 2 scans by matching the radiopaque scan prosthesis so that the prosthesis is visible over the underlying bone structure.9 The implant positions are then determined, and the surgical guide template is designed in the computer software by modifying the mesh image of scan prosthesis.2 Recent developments in optical scan technology have allowed the process of image acquisition of the scan prosthesis by computerized tomography and image format conversion to be replaced by optical scanning of the existing or interim prosthesis.6 The direct digitization of the prosthesis increases the image quality and facilitates the image-matching process. Although the double scan protocol can be used to integrate the planned restoration with the radiographic anatomic data, the radiographic template covers the mucosa and makes it is impossible to visualize the soft-tissue contour of the edentulous ridge.2To integrate the surface scan image of the edentulous ridge into the radiographic scans, a triple scan technique has been proposed.10,11 In this protocol, the first scan is a CBCT of the patient wearing a radiopaque appliance, and the second and third scans are optical scans of the edentulous soft-tissue ridges with and without the placement of the radiopaque appliance. The 3 scans are then matched to each other using the radiopaque appliance as the reference so that the planned restoration and anatomical information can be displayed simultaneously. The triple scan protocol has been reported to be an effective method for implant surgical guide fabrication11; however, as the number of scans and the number of image-matching steps increase, the matching accuracy may be compromised.12 Moreover, there could be discrepancies between the acquired image of the edentulous soft-tissue ridge and the actual form encountered during application of the guide template because of the limitations in intraoral scanning or the possible errors in the conventional impression and stone cast fabrication processes.13Image matching in the double and triple scan techniques can be achieved only with a fully adapted radiopaque scan appliance,14 which is commonly fabricated by duplicating existing or interim dentures of the patient using radiopaque materials,15 or the direct incorporation of radiopaque point-based markers, such as gutta-percha points, ceramic or metallic spheres, metal tubes, or metal strips into the patient's existing or interim dentures.8,16,17 The fabrication process is labor intensive and requires considerable working time. Voids and inaccuracies may arise during the manual processing and result in inaccurate image matching, improper implant position, or inadequate adaptation of the surgical guide to the soft tissues.11 Moreover, although the radiopaque point markers are widely used for image matching, factors such as the position, distribution, number, shapes, and scattering effects of the markers could negatively affect the accuracy of image matching.18This article aims to introduce a radiopaque tissue surface-based digital registration technique that allows the appropriate visualization and registration of the edentulous soft-tissue ridge to the radiographic anatomic data. This workflow can streamline the image-matching process and improve the fit accuracy of the implant surgical guide by eliminating the use of extra scan prostheses or markers, as well as the need for additional image acquisition for the soft-tissue ridge.A 55-year-old male edentulous patient presented with the chief complaint of an ill-fitting complete mandibular denture. Clinical examination and radiographic assessment revealed severe alveolar bone resorption in the posterior region on both sides (Figure 1). Several restorative treatment options, including a new complete denture, implant-retained overdenture, and an implant-supported fixed dental prosthesis, were discussed with the patient. Considering the available bone and the condition of the opposing maxillary complete denture, an implant overdenture retained with stud-type attachments in the anterior area was the preferred prosthesis to restore the edentulous mandible.A computer-guided implant surgical template was fabricated using the following protocol for restoration-driven implant placement. First, a mandibular recording base and wax occlusal rim was made, and the mandible position in the centric relation was determined by using the bilateral manipulation technique described by Dawson.19 Simultaneously, the occlusal vertical occlusion was determined considering facial esthetic appearance, swallowing pattern, phonetics, and interocclusal clearance in a resting upright position.20 Thereafter, a full-arch impression of the mandible was acquired using a radiopaque impression material (Permlastic regular, Kerr Corp, Romulus, Mich) and closed-mouth impression technique (Figure 2). The patient was instructed to move the lips, cheeks, and tongue as in the process of denture relining.21 A radiographic image of the patient with the radiopaque impression was obtained using a CBCT scanner (PaXFlex3D, Vatech Co, Hwasung, Korea) with a field of view of 120 × 85 mm, voxel size of 0.2 mm, and exposure conditions of 90 kVp, 10 mA, and 24-second pulsed scan. The CBCT data were saved in digital imaging and communications in medicine format. The impression body (Figure 3) and the maxillary denture were digitized using an intraoral scanner (CS 3600, Carestream, Rochester, NY), and the scan files were saved in standard tessellation language (STL) file format. The impression body scan was the negative imprint of the edentulous arch (Figure 4), which was reversed using the “flip normal” function of the computer software (Geomagic Design X, 3D Systems, Rock Hill, SC; Figure 5) to generate a digital model of the edentulous ridge. The generated edentulous model and maxillary denture scan files were exported to the computer design software (Ceramill Mind, AmannGirrbach AG, Koblach, Austria), where a virtual teeth arrangement was performed to visualize the prosthetic plan and determine the position of implant insertion (Figure 6).All acquired radiographic and mesh data were imported into the implant-planning software (R2GATE 2.0, MegaGen Implant, Daegu, Korea) for fabricating an implant surgical guide template. The digital model of the edentulous ridge was accurately registered to the 3D radiographic image using the radiopaque impression that was a replica of the soft-tissue surface of the edentulous ridge, as a reference (Figures 7 and 8). The whole surface image of the edentulous ridge was used as the fiducial area in the image registration process (Figure 9). The implant positions were then determined based on the anatomic and prosthetic aspects (Figure 10), and an acrylic resin guide template was fabricated using a 3D printing process (Objet Eden 260VS, Stratasys, Eden Prairie, Minn).The fit of the fabricated guide to the underlying supporting soft tissue was accessed clinically using a silicone fit indicator paste (Fit Checker Advanced, GC Corp, Tokyo, Japan). To quantify the fit discrepancy, 2 optical scan images of the inner surface of the surgical guide template were obtained during the try-in process before and after the application of the fit indicator paste and superimposed using the best-fit registration algorithm of an image analysis software (Geomagic Design X, 3D Systems). The general aspect of the geometric discrepancy between the 2 scans was illustrated in a color-coded map (Figure 11), and the mean discrepancy value was calculated as 0.072 mm using the root mean square error as follows22: where x1,i is the measuring point i on the reference image, x2,i is the measuring point i on the scanned image, and n is the total number of measuring points. The polysulfide-based impression material has been widely used for taking impressions of edentulous jaws because of its high degree of flow and flexibility that allows precise recording of the finest details of the anatomical landmarks.23 In this study, the polysulfide was used as a relining material during the fabrication of a computer-guided implant surgical template due to its radiopacity. The radiodensity of the polysulfide is similar to that of human enamel at 241.94 Hounsfield units (HU)24 and is markedly different from those of the gingiva (50 HU), acrylic resin (70 HU), and cortical bone (1700 HU).25 Accordingly, the polysulfide layer was discernible in the CBCT image and played the role of a fiducial marker in registering the optical scan of the appliance to the CBCT data. Especially in this study, the fiducial marker was presented in the form of a continuous layer on the edentulous dental arch. The surface-based image-matching method is probably more accurate than the point-based method because it allows the use of numerous fiducial points spread all over the surface of the jaw.3–5 Moreover, in this study, the matching area was adjacent to the underlying bone that was the surgical site of implant surgery; thus, the substantive accuracy of image matching was expected to be higher than in cases that use additional external markers far from the surgical site.Ill-fitting implant surgical guide templates lead to instability and unexpected positional deviations of the guide during the drilling process that could reduce the accuracy of the implant placement.26,27 In this report, the misfit of the fabricated guide was measured at 0.072 mm, which was smaller than the previously reported mean gap value of the 3D-printed implant surgical guides for edentulous jaws ranging from 0.78 mm to 1.90 mm.26 The favorable adaptation of the surgical guide template to the soft-tissue surface allows the direct conversion of a digitized dynamic impression of the soft-tissue surface into the digital edentulous model. In the presented technique, the impression material lining the tissue side of the recording base was directly scanned, and then the mesh image of the impression was spatially reversed to generate the digital model of the edentulous ridge. Because the impression scan image was a replica of the reverse image of the dental arch surface, the digital model of the edentulous ridge could be directly generated by inverting the mesh image of the impression, and possible errors associated with the stone cast fabrication and intraoral scanning could be eliminated. This direct digitization of the impression body has previously been reported to be reliable, and along with the image reversal process, it provided a close fit of the surgical template.28,29With the recent advent of a wide variety of computer-assisted design/computer-assisted manufacturing (CAD-CAM) techniques, digitalization has become increasingly prevalent in the field of implant treatment.30,31 The oral anatomic shape is registered virtually using an optical scanner and CBCT devices, and the scan data are then used for fabricating the implant surgical guides, milled models, customized abutments, and definitive prostheses.32 The current optical scanners are reportedly reliable for taking an impression of the intraoral structures; moreover, newly developed 3D face scanners can be used in face analyses to increase the predictability of treatments and optimization of the esthetic results.33 Once the scans were recorded as mesh data in STL format, the data can be used for diverse purposes in computer software programs. The simulation surgery can be performed in the virtual oral cavity environment of implant-planning software.34 The guide templates and prosthetic components can be designed on the mesh data in the CAD software. The adaptation of the fabricated prostheses and guide templates can be evaluated using inspection software.35 Moreover, the obtained scan data can be used for the 3D finite element analysis in simulation software, where the numerical model of anatomic structures, implant components, and prostheses are computerized to achieve a variety of static and dynamic simulation analysis of the mechanical properties.36,37 Another benefit associated with the application of digital workflow is the versatility of data storage for scientific research or future clinical modifications.34Limitations of this method include the need of computer software for the image reversal process and the learning time for the digital technique in this workflow. Further in vitro and clinical studies are needed to compare the effects of this protocol with other image registration techniques in terms of accuracy and convenience.In this article, a virtual edentulous model was digitally generated by inverting the radiopaque impression of the soft-tissue ridge. This radiopaque tissue replica also played as a surface-based fiducial marker that allowed the virtual edentulous model to be accurately registered to the radiographic data. The presented workflow could enhance the accuracy of computer-guided implant surgery by improving the image registration process and increasing the fit of the surgical template.The authors declare that they have no conflict of interest. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (2020R1A2C4002518).

This report describes the case of a 68-year-old man who visited our department complaining of poor denture retention and difficulty masticating due to damage to the retainer of a maxillary obturator. The patient had never been satisfied with the fit of this prosthesis, which had been placed two years earlier. The obturator and the mucosal surface of the denture base were incompatible, which had caused the retainer to detach. The maxillary defect was categorized as H3S0D0T0 according to the HS classification. The diagnosis was a masticatory disorder due to a damaged retainer and an incompatible denture base. Optical impressions and occlusal records were taken and a maxillary obturator fabricated using a CAD/CAM system. Dental CAD software was used to design and complete the tooth arrangement. The CAM system was used to mill a polyetherketoneketone disc based on the obtained data and composite resin used to face the teeth and gingiva. The maxillary obturator was placed after only three visits, spanning from impression taking to denture completion. The use of digital data allowed the time to denture completion to be shortened in addition to the number of hospital visits to be reduced. Compared to conventional impression taking, optical impressions also prevent discomfort, decreasing stress for the patient.

<b>Objective:</b> To quantitatively evaluate the adaptation of polylactic acid (PLA) pattern of mandibular complete denture fabricated by fused deposition modeling (FDM) technology. <b>Methods:</b> A mandibular complete denture digital model was designed through a complete denture design software based on a pair of standard maxillomandibular edentulous plaster model and their occlusion bases. Ten PLA mandibular complete dentures were printed with a FDM machine. The dentures were scanned with and without the plaster model using a three-dimensional (3D) scanner. In Geomagic software, the scanning data of printed dentures were registered to its computer aided design (CAD) data, and the printing error was analyzed using the multipoint registration command. For quantitatively evaluating the adaptation of the denture, the data of plaster model and PLA denture were registered to the whole data of denture located in the plaster model using the best-fit alignment command, the 3D deviation of the plaster model and tissue surface of the denture represent the space between them. The overall area was separated into three parts: primary stress-bearing area, secondary stress-bearing area and border seal area, and the average deviations of these three parts were measured. The values were analyzed using analysis of variance. <b>Results:</b> Compared with the CAD data, the printing error was (0.013±0.004) mm. The overall 3D deviation between PLA denture and plaster model was (0.164±0.033) mm, in which the primary stress-bearing area was (0.165± 0.045) mm, the secondary stress-bearing area was (0.153 ± 0.027) mm, the border seal area was (0.186 ± 0.043) mm. These showed a good fit in the majority parts of the FDM denture to the plaster model. No statistically significant difference was observed between the three areas (<i>F</i>=1.857, <i>P</i>=0.175>0.05). <b>Conclusions:</b> Combined with the 3D scanning, CAD and FDM technology, a FDM 3D printing process of complete denture for injection moulding can be established. As a result, high efficiency and low cost can be used to print out the complete denture, to lay the basis for further clinical applications.

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<b>Background.</b> This study aimed to evaluate the surface scale changes in the denture base material using different polymerization techniques, such as heat-cure/pressure polymerization system and injection molding technique with the stereophotogrammetric technique. The function of a complete denture is related to the adaptation of its base to the supporting areas. Proper adaptation of the base depends on the stability and retention of dentures. The surface scale changes of dentures during processing and in service are of great importance since they affect the denture base material's fit. <b>Methods.</b> This study focused on the use of a computer-assisted stereophotogrammetric method for measuring changes in the volume of three different denture base resins of an edentulous maxillary ridge. A stone master model simulating the shape of an edentulous maxillary arch was used to prepare three groups of denture base resins. The stereophotographs were evaluated to determine the surface scale differences of maxillary jaws. <b>Results.</b> The results showed no significant differences between the denture borders for three denture base materials (<i>P</i> > 0.05). <b>Conclusion.</b> In the evaluation made using this technique, no significant difference was found in the different polymerization techniques in terms of surface scale changes for three denture base materials. Stereophotogrammetry, especially the digital stereophotogrammetric technique, has several useful research applications in prosthodontics.

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Intraoral digital impressions have been stated to meet the clinical requirements for some teeth-supported restorations, though fewer evidences were proposed for larger scanning range. The aim of this study was to compare the accuracy (trueness and precision) of intraoral digital impressions for whole upper jaws, including the full dentitions and palatal soft tissues, as well as to determine the effect of different palatal vault height or arch width on accuracy of intraoral digital impressions. Thirty-two volunteers were divided into three groups according to the palatal vault height or arch width. Each volunteer received three scans with TRIOS intraoral scanner and one conventional impression of whole upper jaw. Three-dimensional (3D) images digitized from conventional gypsum casts by a laboratory scanner were chose as the reference models. All datasets were imported to a specific software program for 3D analysis by "best fit alignment" and "3D compare" process. Color-coded deviation maps showed qualitative visualization of the deviations. For the digital impressions for palatal soft tissues, trueness was (130.54±33.95)μm and precision was (55.26±11.21)μm. For the digital impressions for upper full dentitions, trueness was (80.01±17.78)μm and precision was (59.52±11.29)μm. Larger deviations were found between intraoral digital impressions and conventional impressions in the areas of palatal soft tissues than that in the areas of full dentitions (p<0.001). Precision of digital impressions for palatal soft tissues was slightly better than that for full dentitions (p = 0.049). There was no significant effect of palatal vault height on accuracy of digital impressions for palatal soft tissues (p>0.05), but arch width was found to have a significant effect on precision of intraoral digital impressions for full dentitions (p = 0.016). A linear correlation was found between arch width and precision of digital impressions for whole upper jaws (r = 0.326, p = 0.034 for palatal soft tissues and r = 0.485, p = 0.002 for full dentitions). It was feasible to use the intraoral scanner to obtain digital impressions for whole upper jaws. Wider dental arch contributed to lower precision of an intraoral digital impression. It should be confirmed in further studies that whether accuracy of digital impressions for whole upper jaws is clinically acceptable.

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Relief of the intaglio surface of a denture base is conventionally performed using thin wax and soft metal foil attached to the master cast. The following report highlights a new relief procedure for the mental foramen using a CT double scan technique on the CAD/CAM dentures fabricated for the patient with paresthesia of the left lower lip and chin during mastication.

This study compared the biocompatibility, mechanical properties, and surface roughness of a pre-polymerized polymethyl methacrylate (PMMA) resin for CAD/CAM complete removable dental prostheses (CRDPs) and a traditional heat-polymerized PMMA resin. Two groups of resin substrates [Control (RC): conventional PMMA; Test (RA): CAD/CAM PMMA] were fabricated. Human primary osteoblasts and mouse embryonic-fibroblasts were cultured for biocompatibility assays. Mechanical properties and surface roughness were compared. ANOVA revealed no difference between the resin groups in the biocompatibility assays. RA demonstrated a higher elastic modulus (p=0.002), young's modulus (p=0.002), plastic energy (p=0.002), ultimate strength (p=0.0004), yield point (p=0.016), strain at yield point (p=0.037), and toughness (p<0.0001); while RC displayed a higher elastic energy (p<0.0001). Laser profilometry concluded a rougher surface profile (p<0.0001) for RA. This study concluded that the tested CAD/CAM resin was equally biocompatible and presented with improved mechanical properties than the traditional heat-polymerized PMMA resin used in the fabrication of CRDPs.

The CAD group displayed the best flexural properties, except for FS, the lowest roughness before polishing and bacterial adhesion after 90 minutes of incubation. All tested PMMAs had similar surface roughness after polishing, and microbial adhesion after 16 hours of incubation.

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With ever-growing aging population and demand for denture treatments, pressure-induced mucosa lesion and residual ridge resorption remain main sources of clinical complications. Conventional denture design and fabrication are challenged for its labor and experience intensity, urgently necessitating an automatic procedure. This study aims to develop a fully automatic procedure enabling shape optimization and additive manufacturing of removable partial dentures (RPD), to maximize the uniformity of contact pressure distribution on the mucosa, thereby reducing associated clinical complications. A 3D heterogeneous finite element (FE) model was constructed from CT scan, and the critical tissue of mucosa was modeled as a hyperelastic material from in vivo clinical data. A contact shape optimization algorithm was developed based on the bi-directional evolutionary structural optimization (BESO) technique. Both initial and optimized dentures were prototyped by 3D printing technology and evaluated with in vitro tests. Through the optimization, the peak contact pressure was reduced by 70%, and the uniformity was improved by 63%. In vitro tests verified the effectiveness of this procedure, and the hydrostatic pressure induced in the mucosa is well below clinical pressure-pain thresholds (PPT), potentially lessening risk of residual ridge resorption. This proposed computational optimization and additive fabrication procedure provides a novel method for fast denture design and adjustment at low cost, with quantitative guidelines and computer aided design and manufacturing (CAD/CAM) for a specific patient. The integration of digitalized modeling, computational optimization, and free-form fabrication enables more efficient clinical adaptation. The customized optimal denture design is expected to minimize pain/discomfort and potentially reduce long-term residual ridge resorption.

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Intraoral scanners (IOSs) have emerged as a cornerstone technology in digital dentistry. This article examines the recent advancements and multifaceted applications of IOSs, highlighting their benefits in patient care and addressing their current limitations. The IOS market has seen a competitive surge. Modern IOSs, featuring continuous image capture and advanced software for seamless image stitching, have made the scanning process more efficient. Patient comfort with IOS procedures is favorable, mitigating the discomfort associated with conventional impression taking. There has been a shift toward open data interfaces, notably enhancing interoperability. However, the integration of IOSs into large dental institutions is slow, facing challenges such as compatibility with existing health record systems and extensive data storage management. IOSs now extend beyond their use in computer-aided design and manufacturing, with software solutions transforming them into platforms for diagnostics, patient communication, and treatment planning. Several IOSs are equipped with tools for caries detection, employing fluorescence technologies or near-infrared imaging to identify carious lesions. IOSs facilitate quantitative monitoring of tooth wear and soft-tissue dimensions. For precise tooth segmentation in intraoral scans, essential for orthodontic applications, developers are leveraging innovative deep neural network-based approaches. The clinical performance of restorations fabricated based on intraoral scans has proven to be comparable to those obtained using conventional impressions, substantiating the reliability of IOSs in restorative dentistry. In oral and maxillofacial surgery, IOSs enhance airway safety during impression taking and aid in treating conditions such as cleft lip and palate, among other congenital craniofacial disorders, across diverse age groups. While IOSs have improved various aspects of dental care, ongoing enhancements in usability, diagnostic accuracy, and image segmentation are crucial to exploit the potential of this technology in optimizing patient care.