Abstract:

Objective To investigate the intensity changes of different thickness ratios of Empress Ⅱ glass ceramic and GI-Ⅱ glass-infiltrated alumina ceramic before and after Hertzian contact cyclic fatigue. Methods Disk-shaped specimens of different thickness ratios of EmpressⅡglass ceramic and GI-Ⅱglass-infiltrated alumina ceramic were respectively fabricated. Hertzian contact technique was imposed on the specimens. Critical loads of the specimens before and after 105 cycles loading were recorded. Results The average values of critical loads of all specimens reduced significantly after cycles loading（P<0.05）, and critical loads declined with diminishing thickness of the core ceramic. The critical load of GI- Ⅱ glass-infiltrated alumina ceramic was significantly higher than Empress Ⅱ glass ceramic before and after cycle loading（P<0.05）. Conclusion Cycle loading can reduce the strengths of the two kinds of dental ceramic, and the latter is better than the former in the resistance to fracture and cyclic fatigue. Critical loads of the two kinds of dental ceramic are mainly influenced by the core ceramic′s strength and thickness.

Key words: dental ceramic, thickness ratio, cycle fatigue, critical load