In vitro fracture resistance of composite-resin-veneered zirconia crowns.

Aims: The aim of this study is to investigate the fracture load to failure and damage mode of the composite resin-veneered zirconia crowns preparing with two different zirconia surface treatments compared conventional porcelain-veneered zirconia crowns.

Materials and Methods: Metallic molar-shape dies prepared with 10° convergence angle a 1.5 mm deep chamfer finish line were used. Two groups of composite-resin-veneered zirconia crowns were prepared using different surface treatment (Group A - sandblasting and Group B - glaze-on technique). Group C (conventional porcelain-veneered zirconia crowns) was served as control. Load to failure test was performed to evaluate the fracture resistance of the crowns using a universal testing machine. One-way ANOVA was used to evaluate the differences of mean values ( P < 0.05) followed by Tukey's honest significance test multiple comparisons.

Results: The mean fracture load to failure of Group A was 1078.45 ± 72.3, Group B was 1215.68 ± 100.76, and Group C (control) was 1203.67 ± 88.05. Modes of failure are 100% bulk fracture of the core through the veneering materials for Group B and C. However, Group A showed 40% delamination of composite veneering leaving zirconia coping exposed.

Conclusions: Group B and C showed significant higher load to failure than Group A. Four specimens of Group A revealed the delamination of composite resin veneering.