不同牙周膜厚度对桩核-牙根联合体抗折力学性能的影响

目的探讨不同牙周膜厚度对桩核- 牙根联合体抗折力学性能的影响。方法用有机玻璃模拟标准尺寸的上中切牙牙根45个。常规铸造桩核修复，软衬材料模拟牙周膜，厚度分别为0.2 mm、0.4 mm、0.6 mm、0.8 mm、1.0 mm，试件分成5组，每组9个。在Instron- 4302万能测试机上进行垂直于牙根长轴加载压缩测试，加载速度1 mm/min，至桩核松动、脱位或牙根脱位、破裂，记录最大载荷和位移。结果牙周膜厚度分别为0.2 mm、0.4 mm、0.6 mm、0.8 mm、1.0 mm时，桩核- 牙根联合体承受的平均载荷分别是148.033 N、161.889 N、168.667 N、181.589 N、194.622 N，位移分别为1.965 mm、2.837 mm、3.327 mm、3.927 mm、5.326 mm。除0.4 mm与0.6 mm组，不同牙周膜厚度组间联合体抗折力与位移均有显著性差异。结论牙周膜厚度在一定范围时，相同质量、相同高度牙周膜的桩核- 牙根联合体抗折力和位移与其牙周膜厚度成正比。

Effect of the Thickness of Periodontal Ligament on the Fracture Resistance of Root and Post-core System

OBJECTIVE: To assess the effect of the thickness of periodontal ligament on the fracture resistance of root and post-core system. METHODS: Forty-five simulated roots in the same length, taper and diameter were made of polymethacrylate (PMMA). Then the wax patterns of post-cores were cast. Soft lining material was used to simulated periodontal ligament. And each specimen was embedded in acrylic resin and then fixed in a special jig on the universal load-testing machine. A compressive load was applied at a 90-degree angle to the long axis of the core until fracture, at a crosshead speed of 1 mm/min. The maximum of load and the displacement were recorded. RESULTS: The mean values of load in root and post-core system were 148.033 N, 161.889 N, 168.667 N, 181.589 N, 194.622 N, and the mean values of displacement were 1.965 mm, 2.837 mm, 3.327 mm, 3.927 mm, 5.326 mm. CONCLUSION: The fracture resistance and displacement of root and post-core system with the same quality and altitude periodontal ligament are associated with the thickness of periodontal ligament when the range of thickness is from 0.2 mm to 1.0 mm.