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). RESULTS: No statistically significant difference was found between initial and final marginal gap values (P>.05). At the internal gap measurements, final marginal area values (59.54 µm) were significantly lower than the initial marginal area values (68.68 µm)(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.

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.

Bond strength and stability of 3 luting systems on a zirconia-dentin complex.

This study compared the bond strength and stability of 3 different luting systems to a zirconia ceramic crown. Sixty cylinders of zirconia ceramic were cemented to flat dentin surfaces of extracted human teeth, using 3 different luting agents (n = 20): a glass ionomer (GI) cement, a resin-modified glass-ionomer (RMGI) cement, and a resin cement containing 10-methacryloyloxydecyl dihydrogen phosphate (MDP). The specimens from each cement group were then divided into 2 subgroups (n = 10). Three subgroups (1 from each cement) were selected to test shear bond strength (SBS) immediately before an aging process of thermocycling and water storage, the remaining 3 subgroups were tested for SBS after the aging process. The aging process affected the bond strength of the MDP and RMGI cements. The MDP cement demonstrated superior bond strength compared to the GI and RMGI cements; the GI cement consistently had the lowest bond strength. The RMGI cement had higher cohesive failures at cement (70%), while the GI and the MDP cements had higher percentages of adhesive failure at the ceramic-cement interface (70% and 100%, respectively). The MDP cement promoted better adhesion between dentin and the zirconia ceramic.