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Statement of Problem: Airborne-particle abrasion of titanium is a clinically accepted method of surface preparation. As a side effect of airborne-particle abrasion, particles of the abrasive material get embedded into the surface. How particle presence or removal from the titanium surface affects the strength of the titanium-ceramic bond is unclear., Purpose: The purpose of this in vitro study was to determine the effect of removing Al 2 O 3 particles embedded into the surface by means of chemical surface treatment on the strength of the titanium-ceramic bond., Material and Methods: Titanium (TritanCpTi 1, Dentaurum, 99.5% Ti) disks were airborne-particle abraded with 110 μm Al 2 O 3 at a pressure of 0.4 MPa and an angle of approximately 45 degrees. The surface was etched chemically using 1 of 8 reagents, and the veneering ceramic applied and fired. The strength of the metal-ceramic bond was determined using the shear strength test. Further, the effect of thermal fatigue on the bond strength was evaluated. The results were analyzed with 2-way ANOVA and the Tukey honest significant difference (HSD) test (α=.05). Fractographic investigations and microscopic tests were also performed to determine the quality of the titanium-ceramic bond., Results: Effective etching of the titanium surface and removal of Al 2 O 3 particles included a 30% water solution of HNO 3  + 3% HF, a mixture of HNO 3  + HF + glycerin, a 4% solution of HF in H 2 O 2 , and a 4% solution of HF in H 2 O. A statistically significant difference (of about 50%) in bond strength was found between the groups subjected to chemical etching and the control group (P<.05). Additionally, a statistically significant difference (about 25%) was found after thermocycling (P<.05)., Conclusions: Removing the Al 2 O 3 particles embedded into the titanium surface after airborne-particle abrasion lowers the strength of the titanium-ceramic bond (P<.05). Thermocycling also weakens the strength of the titanium-ceramic bond, regardless of the surface preparation (P<.05)., (Copyright © 2018 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: Ill-fitting restorations can jeopardize dental, periodontal, and systemic health. Repeated ceramic firing may influence the fitting accuracy of restorations, but scientific information regarding this issue is lacking., Purpose: The purpose of this in vitro study was to assess and compare the influence of repeated firings on the marginal, axial, axio-occlusal, and occlusal fit of metal-ceramic 3-unit fixed partial dentures (FPDs) manufactured with different framework methods, including casting, fully sintered hard alloy milling (FHAM), presintered soft alloy milling (PSAM), and selective laser sintering (SLS)., Material and Methods: A total of 60 Co-Cr metal frameworks for 3-unit FPDs were fabricated with 3 different computer-aided design and computer-aided manufacturing (CAD-CAM) techniques and conventional casting for a typodont model. The discrepancy values for premolar and molar abutments were measured by using the silicone replica technique after fabrication of the framework, second firing, fourth firing, and seventh firing. The replicas were separated into mesiodistal and buccolingual cross-sections, and digital images of the cross-sections were obtained with a stereomicroscope at ×80 magnification. The measurement points were examined to record the discrepancy values (μm) with in-built measuring software. The recorded data were subjected to repeated-measures 4-way ANOVA and the Bonferroni post hoc test (α=.05)., Results: For all measurement periods, the marginal, axial, axio-occlusal, and occlusal discrepancy values differed significantly among the manufacturing groups (P<.001). Moreover, the repeated firings had a statistically significant influence on the discrepancy values of PSAM, FHAM, and SLS groups (P<.05). The cast group was not significantly affected by repeated firings (P>.05). The PSAM group revealed the lowest discrepancy values at all measurement periods (P<.05), except after the second firing in the marginal and axial locations., Conclusions: The PSAM-fabricated restorations demonstrated superior fitting accuracy. All manufacturing groups were influenced by repeated firings, except the cast group. The marginal discrepancy values of all manufacturing groups were within the range of clinical acceptability (<120 μm)., (Copyright © 2017 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: 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.)