Abstract
PURPOSE: The purpose of this study was to assess the effect of thermomechanical aging on fracture strength of CAD/CAM (computer aided design and computer aided manufacturing) anterior crowns. MATERIALS AND METHODS: A resin maxillary central incisor was prepared and 96 epoxy resin replicas were obtained. Anterior crowns were produced and divided into four groups: IPS (IPS e.max CAD, 1.5 mmthickness), CD (Celtra Duo, 1.5 mm thickness), GC (GC Initial UHT, 1.5 mm thickness) and GC1 (GC Initial UHT, 1 mm thickness). Twelve crowns of each group were subjected to a chewing simulator for 240,000 cycles, and the other 12 crowns were regarded as control. Fracture resistance of aged and non-aged crowns were tested using a universal testing machine (Shimadzu AGS-X). One-way ANOVA, Tukey post hoc and independent sample t-tests were used to analyze the data and a P value < .05 was considered significant. RESULTS: IPS crowns without aging had the highest (2094.3 ± 399.31 N), and the GC1 crowns after aging had the lowest (1216.99 ± 302.96 N) fracture strength values. The difference of fracture strength among the same thickness samples without aging was not statistically significant (P > .05). The fracture strength of the GC1 group was significantly lower than those of the other groups (P < .05). After aging; GC group showed significantly higher fracture strength than the IPS and GC1 groups. The CD group's fracture strength was significantly higher than the GC1 group (P < .05). Aging significantly decreased the fracture strength of the IPS group (P < .05). CONCLUSION: All monolithic crowns employed in this research proved to be resistant to physiological chewing forces in the anterior region.