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Statement of Problem: Attaining a passive fit in implant restorations is desirable but clinically difficult to achieve, especially in screw-retained prostheses. At a certain magnitude, this misfit will not cause mechanical and biological complications, but the exact level has yet to be determined., Purpose: The purpose of this systematic review was to gather, compare, and appraise studies that attempted to determine the biological and mechanical tolerance of misfits., Material and Methods: The review protocol was published in the Prospective Register for Systematic Reviews (PROSPERO; registration no. CRD42021268399) and follows the Preferred Reporting for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. An electronic search was conducted through PubMed, Ebscohost, and Web of Science followed by a manual search up to December 2021., Results: A total of 413 manuscripts were identified by electronic and manual search. After removing duplicates, nonrelevant titles, and abstract screening, 62 manuscripts were eligible for full-text assessment. Finally, a total of 13 articles (1 cross-sectional study, 1 retrospective and prospective, 7 in vitro studies, and 4 animal studies) met the eligibility criteria and were included in this review. A wide range of tolerable misfits were reported. Vertical misfit up to 1 mm and horizontal misfit up to 345 μm were associated with no adverse outcomes., Conclusions: The current literature provides inadequate data to determine a clinical threshold of an acceptable misfit. However, this review demonstrated that the mechanical response to misfit is more critical than the biological response., (Copyright © 2022 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: Studies that evaluated the effect of dental technician disparities on the accuracy of presectioned and postsectioned definitive casts are lacking., Purpose: The purpose of this in vitro study was to evaluate the accuracy of presectioned and postsectioned definitive casts fabricated by different dental technicians by using a 3-dimensional computer-aided measurement method., Material and Methods: An arch-shaped metal master model consisting of 5 abutments resembling prepared mandibular incisors, canines, and first molars and with a 6-degree total angle of convergence was designed and fabricated by computer-aided design and computer-aided manufacturing (CAD-CAM) technology. Complete arch impressions were made (N=110) from the master model, using polyvinyl siloxane (PVS) and delivered to 11 dental technicians. Each technician fabricated 10 definitive casts with dental stone, and the obtained casts were numbered. All casts were sectioned, and removable dies were obtained. The master model and the presectioned and postsectioned definitive casts were digitized with an extraoral scanner, and the virtual master model and virtual presectioned and postsectioned definitive casts were obtained. All definitive casts were compared with the master model by using computer-aided measurements, and the 3-dimensional accuracy of the definitive casts was determined with best fit alignment and represented in color-coded maps. Differences were analyzed using univariate analyses of variance, and the Tukey honest significant differences post hoc tests were used for multiple comparisons (α=.05)., Results: The accuracy of presectioned and postsectioned definitive casts was significantly affected by dental technician disparities (P<.001). The largest dimensional changes were detected in the anterior abutments of both of the definitive casts. The changes mostly occurred in the mesiodistal dimension (P<.001)., Conclusions: Within the limitations of this in vitro study, the accuracy of presectioned and postsectioned definitive casts is susceptible to dental technician differences., (Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: The marginal and internal discrepancies of computer-aided design and computer-aided manufacturing (CAD-CAM) endocrowns are unknown., Purpose: The purpose of this in vitro study was to evaluate the marginal and internal discrepancies of endocrowns with different cavity depths by measuring them with microcomputed tomography (μCT)., Material and Methods: Endocrowns (n=48) of 2 different cavity depths (2 mm and 4 mm) were fabricated in 2 different chairside CAD-CAM systems (CEREC AC and E4D). A μCT scan was made before and after cementation. For analysis of the marginal and internal discrepancies, reference points were selected in 2-dimensional views of 3 buccolingual cross-sections and 3 mesiodistal cross-sections. To calculate the total discrepancy volume, the μCT sections were reconstructed 3-dimensional views, and changes in volume and surface area were examined. Statistical analysis was performed using 2-way ANOVA with Bonferroni correction (α=.05)., Results: An endocrown with a 4-mm cavity showed a larger marginal and internal volume than one with a 2-mm cavity. Cementation did not show significant differences in total discrepancy thickness. Discrepancies on the pulpal floor were largest in other sites. Both chairside CAD-CAM systems showed similar discrepancy in the endocrowns., Conclusions: Based on the present study, marginal and internal discrepancies increased depending on cavity depth. Cementation did not increase the dimension of the discrepancy between the restoration and the cavity wall. The discrepancy on the pulpal floor appeared to affect these results., (Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: Marginal and axial discrepancies of metal ceramic restorations are key to their long-term success. Little information is available for metal ceramic restorations fabricated with soft metal milling and laser sintering technologies., Purpose: The purpose of this in vitro study was to compare the marginal, axial, and occlusal discrepancies in single-unit metal ceramic restorations fabricated with new production techniques with those in a single-unit restoration fabricated using a conventional technique., Material and Methods: After the artificial tooth was prepared, impressions were made, and 40 dies were obtained. Dies were randomly divided into 4 groups (n=10). Cobalt-chromium (Co-Cr) cast (C), hard metal milled (HM), laser sintered (LS), and soft metal milled (SM) copings were fabricated. Marginal, axial, and occlusal discrepancies of these copings were measured using the silicone replica technique before and after the application of veneering ceramic. Data were analyzed with repeated measurements 2-way ANOVAs and Bonferroni post hoc tests (α=.05)., Results: Significant differences were found in the increase of marginal discrepancy after the application of veneering ceramic in the LS group (P=.016). However, no significant differences in marginal discrepancy were found whether veneering ceramic was applied to copings before or after in the other groups (P>.05). With regard to marginal and occlusal discrepancies, significant differences were found among the production techniques (P<.001 and P<.05, respectively). No significant differences in axial discrepancies were found among the groups (P>.05)., Conclusion: This in vitro study showed that metal ceramic restorations produced with HM and newly introduced SM techniques exhibited better marginal adaptations than those produced with the LS or C technique., (Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: In existing published reports, some studies indicate the superiority of digital impression systems in terms of the marginal accuracy of ceramic restorations, whereas others show that the conventional method provides restorations with better marginal fit than fully digital fabrication. Which impression method provides the lowest mean values for marginal adaptation is inconclusive. The findings from those studies cannot be easily generalized, and in vivo studies that could provide valid and meaningful information are limited in the existing publications., Purpose: The purpose of this study was to systematically review existing reports and evaluate the marginal fit of ceramic single-tooth restorations after either digital or conventional impression methods by combining the available evidence in a meta-analysis., Material and Methods: The search strategy for this systematic review of the publications was based on a Population, Intervention, Comparison, and Outcome (PICO) framework. For the statistical analysis, the mean marginal fit values of each study were extracted and categorized according to the impression method to calculate the mean value, together with the 95% confidence intervals (CI) of each category, and to evaluate the impact of each impression method on the marginal adaptation by comparing digital and conventional techniques separately for in vitro and in vivo studies., Results: Twelve studies were included in the meta-analysis from the 63 identified records after database searching. For the in vitro studies, where ceramic restorations were fabricated after conventional impressions, the mean value of the marginal fit was 58.9 μm (95% CI: 41.1-76.7 μm), whereas after digital impressions, it was 63.3 μm (95% CI: 50.5-76.0 μm). In the in vivo studies, the mean marginal discrepancy of the restorations after digital impressions was 56.1 μm (95% CI: 46.3-65.8 μm), whereas after conventional impressions, it was 79.2 μm (95% CI: 59.6-98.9 μm), Conclusion: No significant difference was observed regarding the marginal discrepancy of single-unit ceramic restorations fabricated after digital or conventional impressions., (Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: Prosthetic crown fit to the walls of the tooth preparation may vary depending on the material used for crown fabrication., Purpose: The purpose of this study was to compare the marginal and internal fit of crown copings fabricated from 3 different materials., Material and Methods: The selected materials were zirconia (ZirkonZahn system, group Y-TZP), lithium disilicate (IPS e.max Press system, group LSZ), and nickel-chromium alloy (lost-wax casting, group NiCr). Five specimens of each material were seated on standard dies. An x-ray microtomography (micro-CT) device was used to obtain volumetric reconstructions of each specimen. Points for fit measurement were located in Adobe Photoshop, and measurements were obtained in the CTAn SkyScan software environment. Marginal fit was measured at 4 points and internal fit at 9 points in each coping. Mean measurements from the 3 groups were compared by analysis of variance (ANOVA) at the 5% significance level, and between-group differences were assessed with the Tukey range test., Results: The nickel-chromium alloy exhibited the best marginal fit overall, comparable with zirconia and significantly different from lithium disilicate. Lithium disilicate exhibited the lowest mean values for internal fit, similar to zirconia and significantly different from the nickel-chrome alloy., Conclusions: The marginal and internal fit parameters of the 3 tested materials were within clinically acceptable range., (Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: Fabricating implant definitive casts with CAD/CAM technology (Robocasts) from coded healing abutment impressions represents a simpler and innovative alternative to conventional implant impression techniques. However, information about the accuracy of the impressions and the resultant definitive casts is limited., Purpose: The purpose of the study was to evaluate the accuracy of the Robocasts and compare them to those definitive casts fabricated with conventional implant impression techniques (open tray with splinted impression copings technique)., Material and Methods: A reference epoxy resin cast was fabricated and shaped to simulate a dental arch. Two regular platform implant replicas (Biomet 3i Certain, 4.1 mm diameter and 15 mm length) with internal connections were placed 10 mm apart with a 10-degree convergence for one side of the reference resin cast and a 30-degree convergence for the other. Coded healing abutments (Encode) were placed at 3 different heights above the level of the soft tissue replication material (approximately 1, 2, and 4 mm) and served as test groups (E1, E2, and E4), and open trays with splinted impression copings (OTSC) served as a control group. The control group was compared to the impressions of the coded healing abutments by using a standardized measurement protocol. Impressions were made for each group (n=18) and poured with vacuum mixed (100 g powder/20 mL water) Type IV dental stone. The vertical discrepancy (Z axis) between 2 prefabricated passively fitting titanium reference frameworks and the platforms of the implant replicas was measured with an optical comparator applying the 1 screw test. Data were analyzed with Kruskal-Wallis and post-hoc Mann-Whitney U tests, as well as the Wilcoxon signed-rank tests. The Bonferroni correction was used to account for multiple comparisons. The significance level (α) used in a given set of tests was equal to .05 divided by the number of tests performed in that set., Results: The median vertical discrepancy of each coded healing abutment impression group was higher than the corresponding median of the control group (OTSC) for every combination of angulation and position. Kruskal-Wallis tests indicated a statistically significant difference (P<.001) between groups for each angulation/position combination. All post hoc Mann-Whitney U tests indicated statistically significant differences (all P≤.002) between OTSC and the other groups. Differences between the angulations and positions were not statistically significant when accounting for multiple comparisons., Conclusions: The implant definitive casts fabricated from the coded healing abutment impressions were found to be less accurate than those fabricated from the open tray with splinted impression copings technique for restoring 2 paired (10 or 30 degrees) convergent internal connection implants with nonengaging screw-retained splinted 2-unit implant restorations. Accuracy of fit was not influenced by the implant angulation or position for either impression technique or by the Encode healing abutment height for the Encode impression technique., (Copyright © 2013 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.)

Statement of Problem: Titanium is the most biocompatible metal used for dental casting; however, there is concern about its marginal accuracy after porcelain application since this aspect has direct influence on marginal fit., Purpose: The purpose of this study was to determine the effect that metal selection and the porcelain firing procedure have on the marginal accuracy of metal ceramic prostheses., Material and Methods: Cast CP Ti, milled CP Ti, cast Ti-6Al-7Nb, and cast Ni-Cr copings (n=5) were fired with compatible porcelains (Triceram for titanium-based metals and VITA VMK 95 for Ni-Cr alloy). The Ni-Cr alloy fired with its porcelain served as the control. Photographs of metal copings placed on a master die were made. Marginal discrepancy was determined on the photographs using an image processing program at 8 predetermined locations before airborne-particle abrasion for porcelain application, after firing of the opaque layer, and after firing of the dentin layer. Repeated-measures 2-way ANOVA was used to investigate the effect of metal selection and firing stage, and paired t tests were used to determine the effect of each firing stage within each material group (alpha=.05)., Results: ANOVA showed that both metal selection and firing stage significantly influenced the measured marginal discrepancy (P<.001), and there was interaction between the 2 variables (P<.001). Student-Newman-Keuls multiple comparison tests showed that there were significant differences between any 2 metals compared, at each stage of measurement. Paired t tests showed that significant changes in marginal discrepancy occurred with opaque firing on milled CP Ti (P=.017) and cast Ti-6Al-7Nb alloy (P=.003)., Conclusions: Titanium copings fabricated by CAD/CAM demonstrated the least marginal discrepancy among all groups, while the base metal (Ni-Cr) groups exhibited the most discrepancy of all groups tested., (Copyright 2010 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.)

Statement of Problem: One of the most important criteria for the clinical acceptability and longevity of cast restorations is marginal adaptation. However, there is limited information on the accuracy of commonly practiced evaluation techniques., Purpose: This study assessed the effect of preparation design on marginal adaptation. In addition, sensitivity and specificity of clinical evaluations of marginal adaptations of cast restorations were assessed and compared to stereomicroscopy., Material and Methods: Three Ivorine molar teeth of differing designs were prepared: (1) a complete crown preparation with a chamfer finish line, (2) a complete crown preparation with a buccal shoulder and beveled finish line, and (3) a three-quarter crown preparation with proximal boxes and beveled finish line. Twenty-four castings (n = 8) were prepared (Ney technique casting metal). Twelve circumferential sites were identified for examination on each casting using a stereomicroscope, which was interpreted using software (Bioquant 98). The clinical examinations included explorer examination to detect marginal gap by tactile feel, followed by examination with a disclosing media (GC FitChecker). Chi-square tests of independence were used to evaluate the effect of preparation design and compare agreement between examination methods for detection of marginal gap size of greater than or equal to 30 microm (alpha=.05)., Results: The overall marginal adaptation of preparation designs was not significantly different. Results of explorer examination at 30-microm sensitivity and specificity were 46% and 97%, respectively. Similar values for disclosing media at 30 microm were 12% sensitivity and 97% specificity. The overall percent agreement with the stereomicroscope using the explorer was 58.3%, with 23.6% correct acceptance rate and 34.7% correct rejection rate. With respect to detection of marginal fit, the combination of disclosing material with explorer data did not yield significantly improved results (59.4%), as compared to explorer alone. A receiver operator characteristic curve yielded satisfactory sensitivity (0.8) and specificity (0.9) at a gap size value of 124 microm., Conclusion: Within the limitations of this study, the preparation design did not significantly affect the marginal adaptation. Clinical detection, with similar sensitivity and specificity as the stereomicroscope, occurred at marginal openings greater than or equal to 124 microm. Therefore, commonly used clinical evaluation techniques using an explorer and disclosing media may be inadequate for assessments of marginal accuracy.

Statement of Problem: Fabricating a feldspathic porcelain margin on a metal-ceramic restoration with a clinically acceptable marginal fit has proven to be a technique-sensitive procedure. Pressable ceramics are advocated to solve this problem., Purpose: The purpose of this in vitro study was to compare the marginal adaptation of a pressable ceramic system when used with both all-ceramic and metal-ceramic crowns, with a traditional metal-ceramic restoration., Material and Methods: A 1.5-mm, 360-degree chamfer margin was prepared on a typodont maxillary central incisor. Polyether impressions were made and poured in a Type IV dental stone, and the following crowns were fabricated on individual dies: 15 metal ceramic restorations (MCR) (Ceramco II, Ceramco, and Argelite 60), 15 pressed-to-metal restorations (PTM) (CPC-MK, and Argelite 60), and 15 pressed ceramic restorations (PCR) (CPC-MK). The marginal fit of the crowns was evaluated every 90 degrees around the crown margin circumference under a microscope at original magnification x 45. A 1-way analysis of variance (ANOVA) was used to compare data (alpha=.05)., Results: The mean marginal discrepancy for MCRs was 94 +/- 41 microm, for PTMs, 88 +/- 29 microm, and for PCRs, 81 +/- 25 microm. The 1-way ANOVA showed no significant difference between groups ( P =.568)., Conclusion: The marginal fit of pressed-to-metal (PTMs) and pressed all-ceramic crowns (PCRs) was similar to that of traditional metal-ceramic crowns (MCRs).