Fracture resistance of endodontically treated canines restored with different sizes of fiber post and all-ceramic crowns

PURPOSE: The aim of this study was to determine the fracture resistance and the mode of fracture of endodontically treated teeth restored with different fiber posts and all-ceramic crowns. MATERIALS AND METHODS: Two glass fiber reinforced post systems in two different sizes and polyethylene fiber ribbon in two different thicknesses (n=10) were used. The specimens, restored with all-ceramic crowns, were subjected to a compressive load (in N) delivered at a 130-degree angle to the long axis until a fracture could be noted. The results were analyzed statistically with a One-Way ANOVA test (P<.05). RESULTS: Statistically significant differences were observed between the mean fracture resistance values of Postec, Snowlight, and Kerr Connect thin specimens (P<.0095). The Postec results (395.70 N) were found to be significantly higher than the others. No statistical difference was observed among the thick specimens (P<.2657). The mean fracture resistance values of the Snowlight thick samples were found to be higher than those of the Snowlight thin samples. The specimens were always fractured around the cemento-enamel junction at the palatinal side. No post fracture was observed for the thin Snowlight and Kerr Connect specimens or for the thick Postec and Kerr Connect specimens. Among the common failure types of the specimens, the worst was observed to be the root fracture failure. The highest post dislodgement failure result (80%) was obtained from the thin Kerr Connect specimen. CONCLUSION: In terms of optimizing fracture resistance, the fiber post size selection should be done according to the forces applied to the restored teeth.

Clinical gap changes after porcelain firing cycles of zirconia fixed dentures

PURPOSE: The aim of this study was to measure the changes on the marginal and internal adaptation of zirconia based anterior fixed partial dentures after the porcelain firing process. MATERIALS AND METHODS: A total of 34 anterior fixed partial dentures using LAVA CAD/CAM system (3M ESPE, Germany) were applied. Two silicone replicas were obtained: one is obtained before porcelain firing process (initial) and the other is obtained after porcelain firing process (final), followed by the examination under a binocular stereomicroscope. Kruskal Wallis and Wilcoxon Signed Ranks tests were used for the statistical analysis (P.05). At the internal gap measurements, final marginal area values (59.54 microm) were significantly lower than the initial marginal area values (68.68 microm)(P<.05). The highest and the lowest internal gap values were observed at the incisal/occlusal area and at the marginal area, respectively. In addition, lower internal gap values were obtained for canines than for central incisors, lateral incisors and premolars at the incisal area (P<.05). CONCLUSION: The firing cycles did not affect the marginal gap of Lava CAD/CAM system, but it is controversial for the internal gap.