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Statement of Problem: Digital light processing (DLP) and milling (MIL) are computer-aided design and computer-aided manufacturing (CAD-CAM) systems that have become popular for fabricating definitive complete dentures. However, few studies have compared the accuracy of the ridge laps of diagnostic tooth arrangements fabricated with these systems and their adaptation with the denture base sockets., Purpose: The purpose of this in vitro study was to comparatively analyze the accuracy of the ridge laps of the diagnostic tooth arrangements fabricated by using MIL and different layer thicknesses in DLP., Material and Methods: A virtual definitive complete denture was designed with a CAD software program on a scanned virtual digital cast, divided into diagnostic tooth arrangement and a denture base that accommodated the arrangement, and saved as a standard tessellation language (STL) file. From this file, 27 diagnostic tooth arrangements were fabricated by DLP (50 μm and 100 μm) and MIL. The ridge laps were scanned and overlapped on the file (reference data) to analyze the accuracy (trueness and precision). The ridge laps of all groups were overlapped on the reference denture base data to analyze their adaptation with the sockets. The measurements of the trueness, precision, and adaptation were analyzed statistically by using the nonparametric Kruskal-Wallis test and post hoc Mann-Whitney U test with Bonferroni correction., Results: The diagnostic tooth arrangements showed significant differences among the groups (P<.001). The values were the lowest in the MIL group and highest in the DLP group for the following parameters: trueness root-mean-square (RMS) value, 173 ±7 μm versus 286 ±15 μm; precision RMS value, 22 ±3 μm versus 57 ±20 μm; and adaptation RMS value, 41 ±5 μm versus 112 ±13 μm., Conclusions: Of the 2 diagnostic tooth arrangements fabricated with the CAD-CAM systems, the one fabricated with MIL was clinically more appropriate., (Copyright © 2022 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

This study aims to measure the trueness of zirconia crowns with different build directions of materials fabricated using the stereolithography (SLA) method. The anatomic contour crown of prepped maxillary right first molar was designed using CAD software to obtain the standard tessellation language (STL) file. Two different build directions were set for the crowns using Materialize Magics software. One group was built with a margin base platform, while the other group was built in the direction opposite to the occlusal surface base platform. The 20 crown-shaped parts were printed. The STL files of scanned printing zirconia crowns were superimposed each segment by the 3D analysis software. The two groups were statistically analyzed using t-tests. Significant differences were found in the marginal and internal discrepancies between the groups. The build direction had a significant influence on the accuracy of the zirconia crown. The results indicate the most effective build direction for manufacturing SLA 3D-printed crowns.

Statement of Problem: Conventional fabrication of complete denture metal bases is being replaced by the computer-aided design and computer-aided manufacturing (CAD-CAM) systems. However, a comparative analysis of subtractive and additive CAD-CAM manufacturing techniques is lacking., Purpose: The purpose of this in vitro study was to compare the adaptation of complete denture metal bases fabricated by milling (subtractive manufacturing) and stereolithography apparatus (SLA) and digital light processing (DLP) (additive manufacturing)., Material and Methods: Thirty metal bases were manufactured by using the milling (MIL group), SLA (SLA group), and DLP (DLP group) techniques. The silicone replica technique was used to evaluate the adaptation of the complete denture metal bases, and 30 silicone blocks were fabricated. The silicone block was cut equally in the canine, first molar, and second molar areas. The gap between the model and the metal base was measured by using a digital microscope at the 3 locations, and the measured data were statistically analyzed by using a statistical software program (α=.05)., Results: The gaps measured at the 3 areas showed significant differences in all 3 groups (P<.05). At the anterior, middle, and posterior areas, the SLA group showed the narrowest gap (302 ±31 μm, 241 ±39 μm, 201 ±43 μm, respectively). The SLA group also had the narrowest total gap of the metal bases (218 ±33 μm)., Conclusions: The adaptation of the fabricated metal bases varied significantly across the techniques used but fell within a clinically allowable range. The SLA group was the most precise in the fabrication of complete denture metal bases. Further studies are required to analyze the effects of the layer thickness setting, wax elimination, and casting temperature on the adaptation of metal bases manufactured by using SLA., (Copyright © 2020 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: Layer thickness in additive manufacturing has stair-step effects that greatly affect the accuracy of the definitive prosthesis. Although the layer thickness can be set, insufficient data comparing and analyzing the accuracy of the fabricated prosthesis after adjusting the layer thickness are available., Purpose: The purpose of this in vitro study was to evaluate and compare the accuracy of trial dentures fabricated with different layer thicknesses by using stereolithography (SLA) apparatus., Material and Methods: A maxillary complete edentulous cast was duplicated with silicone material to make a master gypsum cast which was scanned by using a laboratory scanner and saved as a standard tessellation language (STL) file. This was exported into a computer-aided design software program to produce and store the trial denture. Twenty dentures were fabricated according to the set layer thicknesses (50 μm and 100 μm) by using the SLA. The trueness was measured by scanning the intaglio and cameo surfaces to find the best overlap with the reference model to obtain the root mean square value. The precision was evaluated based on the RMS value gained by superimposing the identical scan data from each group and using the combination formula. The Mann-Whitney U-test was used to confirm significant differences among the groups (α=.05)., Results: The trueness of the 50-μm-SLA trial denture and the 100-μm-SLA trial denture was significantly different for the intaglio and cameo surfaces (P<.05). However, the intaglio surface did not show a statistically significant difference (P=.987) for precision, but the cameo surface did (P<.05)., Conclusions: It is clinically more appropriate to set the layer thickness to 100 μm rather than 50 μm for the fabrication of accurate trial dentures by using SLA., (Copyright © 2020 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the accuracy (trueness and precision) of dental replica models produced by using photopolymer materials in additive manufacturing., Materials and Methods: A complete arch model was scanned using an extraoral scanner (Identica Blue) and established as reference. For the control group, 10 stone models were acquired through the conventional method from the reference model. For the experimental groups, digital data were acquired using an intraoral scanner (CEREC Omnicam), and 10 stereolithographic apparatus (SLA) models and 10 PolyJet models were made. All models were scanned with an extraoral scanner. Three-dimensional analysis software was used to measure differences between the 3D scanned images in root mean square values. The ISO-5725-1 specification was followed to measure trueness and precision between two 3D scanned data. Trueness was calculated by overlapping scanned data with the reference model and precision by performing pairwise intragroup comparisons. Also the ratio of region out of tolerance (> ±50 μm) was measured. One-way ANOVA and Tukey's post hoc analysis were applied., Results: There was no statistically significant difference in trueness between the stone and the SLA models (p > 0.05). Dental replica models using photopolymer materials showed statistically significantly better precision than that of the stone model (p < 0.05). Regarding tolerance, no statistically significant difference was observed between the stone and the SLA models (p > 0.05)., Conclusions: Although the dental replica models using photopolymer materials did not show better trueness than the conventional stone models, there was no significant difference between the SLA and the stone models. Concerning precision, dental replica models using photopolymer materials presented better results than that of the conventional stone models. In sum, dental replica models using photopolymer materials showed sufficient accuracy for clinical use., (© 2018 The Authors. Journal of Prosthodontics published by Wiley Periodicals, Inc. on behalf of American College of Prosthodontists.)

Purpose: This study aimed to evaluate and compare the accuracy., Methods: A reference model was prepared with three prepared teeth for three types of restorations: single crown, 3-unit bridge, and inlay. Stone models were fabricated from conventional impressions. Digital impressions of the reference model were created using an intraoral scanner (digital models). Physical models were fabricated using a three-dimensional (3D) printer. Reference, stone, and 3D printed models were subsequently scanned using an industrial optical scanner; files were exported in a stereolithography file format. All datasets were superimposed using 3D analysis software to evaluate the accuracy of the complete arch and trueness of the preparations. One-way and two-way analyses of variance (ANOVA) were performed to compare the accuracy among the three model groups and evaluate the trueness among the three types of preparation., Results: For the complete arch, significant intergroup differences in precision were observed for the three groups (p<.001). However, no significant difference in trueness was found between the stone and digital models (p>.05). 3D printed models had the poorest accuracy. A two-way ANOVA revealed significant differences in trueness among the model groups (p<.001) and types of preparation (p<.001)., Conclusions: Digital models had smaller root mean square values of trueness of the complete arch and preparations than stone models. However, the accuracy of the complete arch and trueness of the preparations of 3D printed models were inferior to those of the other groups., (Copyright © 2018 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.)

Purpose: The purpose of this in vitro study was to compare and analyze the three-dimensional marginal and internal fit of PEKK and zirconia copings., Methods: Two acrylic models of the right maxillary canine, first molar were fabricated as master dies and duplicated by one-step dual viscosity impressions. Five stone replicas from each model were digitized with a blue-light scanner and copings were machined from Pekkton and Zirconia blanks. The inner surface of all the copings and two original acrylic models were digitized by a highly accurate optical scanner. By superimposing the digitized coping data with the CAD-reference die three-dimensionally, visual fit-discrepancies were drawn by calculating the root mean square (RMS) and visualized on a color-difference map. Each calculated RMS-value was statistically analyzed by 3-way ANOVA. In addition, Student's t-test was conducted in order to verify the significance (α=.05) of fit-discrepancies based on the type of abutment tooth and the materials., Results: Mean RMS-values for marginal fit (internal fit) ranged from 51.64±1.5 (36.12±1.34) to 69.62±8.11 (41.6±1.63)μm. Differences in marginal fit (canine: P=.001; molar: P=.047) and internal fit (canine: P=.017; molar: P=.046) were statistically significant. The results of the 3-way ANOVA showed statistically significant differences in the RMS values of the two groups for the material (P<.001), the types of the abutment tooth (P<.001), and the measured region (P<.001)., Conclusions: The marginal and internal fit of both PEKK and zirconia copings of both canine and molar were within the clinically acceptable range. However, the PEKK presented better fitness compared with the zirconia., (Copyright © 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.)

Statement of Problem: Fit is an important factor influencing the success or failure of restorations. Recently, there has been increasing use of a newly developed pre-sintered soft alloy for use in computer-aided design and computer-aided manufacturing (CAD-CAM) of cobalt-chromium alloys for the fabrication of metal ceramic restorations. However, almost no studies are available on the fit of restorations fabricated in this way., Purpose: The purpose of this in vitro study was to evaluate the fit of metal coping fabricated from a newly developed CAD-CAM soft alloy in order to investigate its clinical applicability., Material and Methods: Metal coping was categorized as casting alloy (CA), fully sintered hard alloy (FHA), or pre-sintered soft alloy (PSA) depending on the material, and 10 specimens of each category were fabricated. Seven measurement locations were selected in both the mesiodistal and labiolingual directions. For measurement of the marginal and internal discrepancies, silicone molds produced using a silicone replica technique were divided into mesiodistal and labiolingual cross-sections, and the width was measured. The Kruskal-Wallis and Mann-Whitney U test were performed (corrected α error level=.05/3)., Results: The mean values of the total discrepancy were smallest in the CA group (52.53 ±33.40 μm) and largest in the FHA group (87.84 ±39.43 μm). The CA group and the PSA group were not significantly different from each other (P>.05) but were statistically significantly different from the FHA group (P<.001). In particular, the absolute marginal discrepancy did not differ significantly between the CA (33.68 ±8.44 μm) and PSA groups (37.01 ±8.04 μm) (P>.05)., Conclusions: The fit of the PSA restorations determined by this study was similar to that of conventional cast restorations. Both FHA and PSA restorations demonstrated clinically acceptable values (<120 μm)., (Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: Reproducibility is an important factor determining the success of a prosthesis. However, no studies have focused on identifying the location of errors on prostheses fabricated with the subtractive method, leading to a lack of standards for reproducibility evaluations., Purpose: The purpose of this in vitro study was to evaluate the reproducibility of the subtractive method by conducting 3-dimensional assessments of presintered single-tooth zirconia copings for different teeth., Material and Methods: Acrylic resin tooth molds for the canine (CAN), premolar (PRE), and molar (MOL) were used to prepare stone casts, and copings were designed and fabricated with the subtractive method. The intaglio surfaces of corresponding presintered zirconia copings were scanned with a blue light scanner. Initial scan data were used as a reference for comparisons with subsequent data for the measurement of errors. Nine color-difference maps were created for each of the 3 groups and used to calculate root-mean-square (RMS) error values. One-way analysis of variance and the Tukey honestly significant difference tests were used for statistical evaluations (α=.05)., Results: MOL copings exhibited the highest RMS error value (9.22 ±1.56 μm), which was significantly different from values for CAN (3.33 ±2.65 μm) and PRE (4.00 ±2.40 μm; P<.001) copings. Color-difference maps revealed maximum errors in the line angles., Conclusions: The highest reproducibility was observed for the CAN copings. The clinical reproducibility of the subtractive method can be improved by avoiding sharp angles during abutment preparation and careful reproduction of angles during prosthesis fabrication., (Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Purpose: The precision of two types of surface digitization devices, i.e., a contact probe scanner and an optical scanner, and the trueness of two types of stone replicas, i.e., one without an imaging powder (SR/NP) and one with an imaging powder (SR/P), were evaluated using a computer-aided analysis., Methods: A master die was fabricated from stainless steel. Ten impressions were taken, and ten stone replicas were prepared from Type IV stone (Fujirock EP, GC, Leuven, Belgium). The precision of two types of scanners was analyzed using the root mean square (RMS), measurement error (ME), and limits of agreement (LoA) at each coordinate. The trueness of the stone replicas was evaluated using the total deviation. A Student's t-test was applied to compare the discrepancies between the CAD-reference-models of the master die (m-CRM) and point clouds for the two types of stone replicas (α=.05)., Results: The RMS values for the precision were 1.58, 1.28, and 0.98μm along the x-, y-, and z-axes in the contact probe scanner and 1.97, 1.32, and 1.33μm along the x-, y-, and z-axes in the optical scanner, respectively. A comparison with m-CRM revealed a trueness of 7.10μm for SR/NP and 8.65μm for SR/P., Conclusions: The precision at each coordinate (x-, y-, and z-axes) was revealed to be higher than the one assessed in the previous method (overall offset differences). A comparison between the m-CRM and 3D surface models of the stone replicas revealed a greater dimensional change in SR/P than in SR/NP., (Copyright © 2015 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.)

Objective: This study addresses common errors that may occur during digital impression procedures using the CEREC AC and in-office CAD/CAM systems. Error types and frequencies resulting from digital impressions of the oral cavity were investigated and their origins identified to facilitate the acquisition of more accurate digital impressions., Method and Materials: A total of 1,251 digital impression cases, including 163 onlays and 1,088 inlays, were constructed as restorations using the CEREC AC system. Two evaluators determined five categories of digital errors as a basis for evaluation over two sessions. The five categories were as follows: inappropriate scanner positioning (ISP), improper handling of the scanner (IHS), irregular powder arrangement (IPA), improper cavity preparation (ICP), and insufficient scanned data (ISD)., Results: The most frequently encountered errors were non-linear powder application (IPA), inappropriate oral cavity scanner placement (ISP), and insufficient data (ISD). ISP showed that inlays had a slightly higher frequency of errors, but this observation was not statistically significant (P > .05)., Conclusion: Most errors are caused by incorrect operation of intraoral scanners or uneven application of powder in acquiring digital impressions. To provide optimal digital impression results, careful chairside technique procedures and operation of intraoral scanners are required.

The clinical applicability of CAD/CAM-fabricated zirconia copings is tested using working models made from four different highstrength Type IV gypsum materials. Each of the four materials was used to fabricate 15 zirconia copings. Precision of fit was measured with a digital electron microscope using the silicone replica technique. The mean and standard deviation of each reference point were analyzed using the one-way analysis of the variance (ANOVA) and Tukey's honest significant difference (HSD) tests (α=0.05). The overall marginal and internal fits of the zirconia copings were as follows: GS (GS: Grey Stone) group: 91.43 μm, LS (LS: Light green Stone) Group: 87.89 μm, RS (RS: Red Stone) Group: 88.75 μm, BS (BS: Beige Stone) Group: 82.78 μm. There were no significant differences between the mean adaptations of the gypsum varieties (p>0.05). This confirmed that the type of gypsum material used does not determine the precision of fit of a prosthesis.

Statement of Problem: One of the most important factors in determining the clinical outcomes of fixed dental prostheses is the gap between the fixed dental prosthesis and the abutment. However, reports that investigated these gaps in the context of fixed dental prostheses fabricated with new technologies are few., Purpose: The purpose of this study was to measure and analyze the fit of fixed dental prostheses. The fixed dental prostheses for the study were produced with the subtractive method (milling soft metal blocks), additive method (selective laser sintering), and traditional method (lost wax and casting)., Material and Methods: Ten specimens were fabricated with the soft metal block, selective laser sintering, and lost wax and casting methods. The 3-dimensional measurement method was adopted to obtain the measure gap figures of the specimens. To fabricate a digital replica, computer-aided design reference casts were prepared by scanning the study casts, and silicone replicas were fabricated for each specimen. These silicone replicas were scanned and obtained 40,000 point cloud data. The study also defined the mean gap for each specimen by averaging approximately 40,000 gap points to evaluate the fit of the specimens. Data were analyzed with 1-way ANOVA and the Tukey honestly significant difference (α=.05)., Results: The mean gap was the smallest for fixed dental prostheses fabricated with the soft metal block, followed by the selective laser sintering, then the lost wax and casting. One-way ANOVA revealed statistically significant differences in the size of the gap among the 3 groups (P<.001), and the Tukey honestly significant difference test confirmed the specific differences among the groups (P<.05)., Conclusions: The fit obtained with the new soft metal block and selective laser sintering techniques was better than that obtained with the traditional lost wax and casting method. Thus, fixed dental prostheses produced by using these new techniques can be considered clinically acceptable., (Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

This study analyzed the trueness of polymer-infiltrated ceramic and glass ceramic crowns manufactured using the chairside computer-aided design/manufacturing (CAD/CAM) system. The master model designs crowns using a CAD program after acquiring a digital impression with an intraoral scanner. Vita Enamic (VE), Vita Suprinity (VS), and IPS e.max CAD (IPS) were used to manufacture 10 crowns each (total: 30 crowns), using the chairside CAD/CAM system (inLab MC XL). Trueness was evaluated by superimposing the CAD data on the scan data using a three-dimensional program. The Kruskal–Wallis H test, a nonparametric test, and the Mann–Whitney U test were performed by applying the significance level (0.05/3 = 0.016), which was adjusted by post-analysis Bonferroni testing. There was a significant difference in the trueness between the samples (p < 0.05). However, there was no statistically significant difference in the outer surface trueness between the samples (p > 0.05). These findings show that the milling accuracy of VE is better than that of VS and IPS. [ABSTRACT FROM AUTHOR]

Background: Despite the wide use of dental materials for CAD/CAM system in prosthetic treatment, the effect of the materials, which are used as dental implants core fabricated, on cells involved in dental implant osseointegration is uncertain. This study aimed to investigate and compare the effect of single core materials used for dental implants fabricated by the dental prostheses fabrication process and the CAD/CAM milling method on MC3T3-E1 cells. Methods: The materials used for prostheses restoration in this experiment were Porcelain Fused Gold (P.F.G), Lithium disilicate glass ceramic (LiSi2), Zirconia (ZrO2), Nickel-Chromium (Ni-Cr) and Cobalt-Chromium (Co-Cr). MC3T3-E1 cells were cultured and used, the cell adhesion and morphology were observed and analyzed using confocal laser scanning microscopy (CLSM). Methoxyphenyl tetrazolium salt (MTS) and alkaline phosphatase (ALP) assay were used to observe the cell proliferation and differentiation. Results: CLSM revealed irregular cell adhesion and morphology and the filopodia did not spread in the Ni-Cr specimen group. Significantly high cell proliferation was observed in the ZrO2 specimen group. The LiSi2 specimen group presented significantly high cell differentiation. Intergroup comparison of cell proliferation and differentiation between the Ni-Cr specimen group and all other specimen groups showed significant differences (p <.05). Conclusion: Cell proliferation and differentiation were observed from the cores, which were fabricated with all specimen groups on cytocompatibility except the Ni-Cr specimen group. [ABSTRACT FROM AUTHOR]

The goal of this study was to evaluate the effects of different core and veneer thicknesses on the translucency (T%), average light transmittance (T), translucency parameter (TP), contrast ratio (CR), and spectral reflectance (R) of glass-ceramics using a computer-aided design/computer-aided manufacturing (CAD-CAM) process. In all, 42 specimens (11mm × 11mm) were prepared and divided into six groups (n = 7 for each group). Core materials (IPS e.max CAD; IPS Empress CAD, LT A2 shade) of different thicknesses (0.8, 1.0, and 1.2mm) were fabricated. Each veneer material (thicknesses of 0.7, 0.5, and 0.3mm) was combined with its compatible core ceramic. Each core material was overlapped with its corresponding veneer material to obtain a 1.5-mm thickness by using three different combinations: (0.8+0.7), (1.0+0.5), and (1.2+0.3) mm. A spectrophotometer and color data software were used to measure the T%, T, TP, CR, and R values of each ceramic. The results were statistically analyzed using two-way analysis of variables (ANOVA) and regression analysis (p<0.05). Two-way ANOVA revealed that T%, T, TP, and CR were significantly influenced by the different thicknesses of the core-veneer combinations (p<0.001). At a certain thickness, as the veneer thickness increased and core thickness decreased, T and T% all increased. Regression analysis of the ceramic materials indicated a reduction in T and T% for certain core-veneer combinations. Analysis also revealed that T% and T were all affected by different core-veneer combinations. The T% value was 74.31 for the EM group and 72.81 for the EP group when the thickness of the core was 1.2 mm and the veneer was 0.3 mm. The R value of EM2 was lower than EM1 and EM3. In conclusion, the optical properties were influenced by different core-veneer combinations. [ABSTRACT FROM AUTHOR]

Background: The purpose of this in vitro study is to fabricate a novel metal–ceramic prosthesis with a porous structure, to compensate for the disadvantages associated with the design of existing prostheses, and to measure the internal fit of this prosthesis. Materials and Methods: In this in vitro study, the mandibular first molar was scanned from the dental computer-aided-design to design a 3 mm porous structure frame. The frame was produced using the lamination method and fired in a pressed ceramic. For comparison, pore-free specimens were fabricated by selective laser sintering (SLS) as described above, and porous specimens were fabricated by casting (total n = 30). The internal fit was then measured using a digital microscope (at 100× magnification), and the data were analyzed using one-way ANOVA (α = 0.05). Results: The total mean internal discrepancies for each group were 42.32 ± 22.50 μm for the porous structure SLS group (PS-group), 107.54 ± 38.75 μm for no-porous casting group (group), and 121.36 ± 50.19 μm for the no-porous SLS group (group), with significant differences (P < 0.05) among all groups. Conclusion: The internal discrepancies of porous structure crown fabricated by SLS were smaller than that of no-porous crown fabricated by casting and SLS. Based on these laboratory findings, further studies should be conducted to evaluate the feasibility of the newly designed porous structure and press ceramic prosthesis to determine whether they can be applied in clinical practice. [ABSTRACT FROM AUTHOR]