of zirconia copings

Statement of problem. Proper marginal, axial, and occlusal adaptation of dental restorations is essential for their long-term success. Production protocols including digital impression systems have been developed, but little information is available on the adaptation of zirconia restorations produced via them.Purpose. The purpose of this in vitro study was to compare the effects of digital impression protocols on the marginal, axial, and occlusal adaptation of zirconia copings.Material and methods. Thirty extracted human maxillary premolar teeth without caries or defects were used. The teeth were prepared for zirconia crowns and randomly divided into 3 groups. Zirconia copings were designed at a thickness of 0.5 mm with 30 mu m of simulated die spacer starting 1 mm from the margin of preparations. They were produced using computer-aided design computer-aided manufacture (CAD-CAM) protocol with a conventional impression (group Cn) and 2 different production protocols with digital impressions (group C) and group Tr. The marginal, axial, and occlusal discrepancies of these copings were measured using the silicone replica technique with stereomicroscopy at x50 magnification, and the data were analyzed with 1-way ANOVAs (alpha=.05).Results. The mean marginal discrepancy values were 85.6 mu m for group Cn, 58.7 mu m for group C, and 47.7 mu m for the Tr group. Significant differences were found among the production protocols in marginal, axial, and occlusal discrepancies (P.05), and group Tr revealed the lowest axial discrepancy (P.05).Conclusions. The copings produced with the aid of digital impression systems exhibited better marginal and occlusal adaptation than those of the copings produced with the aid of conventional impression

Effect of repeated ceramic firings on the marginal and internal adaptation of metal-ceramic restorations fabricated with different CAD-CAM technologies.

STATEMENT OF PROBLEM: The use of computer-aided design and computer-aided manufacturing (CAD-CAM) for metal-ceramic restorations has increased with advances in the technology. However, little is known about the marginal and internal adaptation of restorations fabricated using laser sintering (LS) and soft milling (SM). Moreover, the effects of repeated ceramic firings on the marginal and internal adaptation of metal-ceramic restorations fabricated with LS and SM is also unknown. PURPOSE: The purpose of this in vitro study was to investigate the effects of repeated ceramic firings on the marginal and internal adaptation of metal-ceramic copings fabricated using the lost wax (LW), LS, and SM techniques. MATERIAL AND METHODS: Ten LW, 10 LS, and 10 SM cobalt-chromium (Co-Cr) copings were fabricated for an artificial tooth (Frasaco GmbH). After the application of veneering ceramic (VITA VMK Master; VITA Zahnfabrik), the marginal and internal discrepancies of these copings were measured with a silicone indicator paste and a stereomicroscope at ×100 magnification after the first, second, and third clinical simulated ceramic firing cycles. Repeated measures 2-way ANOVA and the Fisher LSD post hoc test were used to evaluate differences in marginal and internal discrepancies (α=.05). RESULTS: Neither fabrication protocol nor repeated ceramic firings had any statistically significant effect on internal discrepancy values (P>.05). Marginal discrepancy values were also statistically unaffected by repeated ceramic firings (P>.05); however, the fabrication protocol had a significant effect on marginal discrepancy values (P.05). CONCLUSIONS: All groups demonstrated clinically acceptable marginal adaptation after repeated ceramic firing cycles; however, the LS and SM groups demonstrated better marginal adaptation than that of LW group and may be appropriate clinical alternatives to LW

adaptation of metal-ceramic restorations fabricated with different

Statement of problem. The use of computer-aided design and computer-aided manufacturing (CAD-CAM) for metal-ceramic restorations has increased with advances in the technology. However, little is known about the marginal and internal adaptation of restorations fabricated using laser sintering (LS) and soft milling (SM). Moreover, the effects of repeated ceramic firings on the marginal and internal adaptation of metal-ceramic restorations fabricated with LS and SM is also unknown.Purpose. The purpose of this in vitro study was to investigate the effects of repeated ceramic firings on the marginal and internal adaptation of metal-ceramic copings fabricated using the lost wax (LW), LS, and SM techniques.Material and methods. Ten LW, 10 LS, and 10 SM cobalt-chromium (Co-Cr) copings were fabricated for an artificial tooth (Frasaco GmbH). After the application of veneering ceramic (VITA VMK Master; VITA Zahnfabrik), the marginal and internal discrepancies of these copings were measured with a silicone indicator paste and a stereomicroscope at x100 magnification after the first, second, and third clinical simulated ceramic firing cycles. Repeated measures 2-way ANOVA and the Fisher LSD post hoc test were used to evaluate differences in marginal and internal discrepancies (alpha=.05).Results. Neither fabrication protocol nor repeated ceramic firings had any statistically significant effect on internal discrepancy values (P >.05). Marginal discrepancy values were also statistically unaffected by repeated ceramic firings (P >.05); however, the fabrication protocol had a significant effect on marginal discrepancy values (P .05).Conclusions. All groups demonstrated clinically acceptable marginal adaptation after repeated ceramic firing cycles; however, the LS and SM groups demonstrated better marginal adaptation than that of LW group and may be appropriate clinical alternatives to LW

adaptation of metal-ceramic restorations fabricated with different

Statement of problem. The use of computer-aided design and computer-aided manufacturing (CAD-CAM) for metal-ceramic restorations has increased with advances in the technology. However, little is known about the marginal and internal adaptation of restorations fabricated using laser sintering (LS) and soft milling (SM). Moreover, the effects of repeated ceramic firings on the marginal and internal adaptation of metal-ceramic restorations fabricated with LS and SM is also unknown.Purpose. The purpose of this in vitro study was to investigate the effects of repeated ceramic firings on the marginal and internal adaptation of metal-ceramic copings fabricated using the lost wax (LW), LS, and SM techniques.Material and methods. Ten LW, 10 LS, and 10 SM cobalt-chromium (Co-Cr) copings were fabricated for an artificial tooth (Frasaco GmbH). After the application of veneering ceramic (VITA VMK Master; VITA Zahnfabrik), the marginal and internal discrepancies of these copings were measured with a silicone indicator paste and a stereomicroscope at x100 magnification after the first, second, and third clinical simulated ceramic firing cycles. Repeated measures 2-way ANOVA and the Fisher LSD post hoc test were used to evaluate differences in marginal and internal discrepancies (alpha=.05).Results. Neither fabrication protocol nor repeated ceramic firings had any statistically significant effect on internal discrepancy values (P >.05). Marginal discrepancy values were also statistically unaffected by repeated ceramic firings (P >.05); however, the fabrication protocol had a significant effect on marginal discrepancy values (P .05).Conclusions. All groups demonstrated clinically acceptable marginal adaptation after repeated ceramic firing cycles; however, the LS and SM groups demonstrated better marginal adaptation than that of LW group and may be appropriate clinical alternatives to LW

metal ceramic restorations produced with new technologies

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 (alpha=.05).Results. Significant differences were found in the increase of marginal discrepancy after the application of veneering ceramic in the LS group (rho=.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.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

Effect of fluid contamination on reverse torque values in bone-level implants.

INTRODUCTION: Screw loosening is one of the most common mechanical complications within the prosthetic components of dental implants. Clinicians must know if reverse torque values (RTVs) are affected by contamination of the implant abutment screw hole with either blood, saliva or chlorhexidine. METHODS: Forty implants were divided into 4 groups (n = 10). Implants were embedded in epoxy resin and placed in a digital torque meter. Screw holes of 30 implants were contaminated with either chlorhexidine (CG), fresh human saliva (SG), or blood (BG), and the remaining noncontaminated screws served as a control group (NC). Abutment screws were tightened using a hand-held torque meter (25 N·cm). Thermocycling (1500 cycles) was performed, and abutment detorque values were calculated using the digital torque meter. RESULTS: RTVs were lower than insertion torque values for all groups. According to Tukey HSD Test, blood contamination of abutment screws resulted in significantly lower RTVs (18.950 ± 2.641 N·cm) when compared with controls. CONCLUSIONS: Blood contamination of abutment screw holes was shown to significantly decrease RTVs. Blood contamination may result in greater loosening of implant screws in clinical practice