厚度配比对2种牙科陶瓷疲劳行为的影响研究

目的考察不同厚度配比的EmpressⅡ热压铸造陶瓷和GI-Ⅱ型氧化铝渗透陶瓷层状复合结构经Hertzian循疲劳前后强度的变化。方法分别制作不同厚度配比EmpressⅡ热压铸造陶瓷和GI-Ⅱ型氧化铝渗透陶瓷圆盘状试件，应用Hertzian接触实验方法对这些试件进行循环加载，然后测试105循环加载前后试件的临界载荷。结果EmpressⅡ热压铸造陶瓷和GI-Ⅱ型氧化铝渗透陶瓷在经Hertzian循环加载后，临界载荷力的平均值比加载前均明显下降（P<0.05），并且载荷力随底层瓷厚度的下降而降低。GI-Ⅱ氧化铝渗透陶瓷在加载前后的临界载荷均明显高于EmpressⅡ热压铸造陶瓷（P<0.05）。结论循环疲劳能显著降低EmpressⅡ热压铸造陶瓷和GI-Ⅱ型氧化铝渗透陶瓷材料的强度，后者在抗碎裂能力和耐受疲劳方面均优于前者，底层瓷的强度和厚度是决定这2种材料临界载荷力的大小的主要因素。

The influence of thickness ratios on the fatigue behaviors of two kinds of dental ceramic

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.