循环加载对不同桩核修复后牙体抗折强度的影响

In vitro analysis of the effect of cyclic loading on the fracture resistance of teeth restored with different post and core systems

目的：用循环加载的方式模拟核桩冠修复一段时间后的状况，比较不同桩核修复后牙体的抗折强度，了解其远期修复效果。方法 15颗下颌离体前磨牙随机分为3组，分别为铸造金属桩核组（A组）、玻璃纤维加强复合树脂桩核组（B组）、树脂充填组（C组），每组5个试件。所有试件在完成桩核修复后均做金属冠修复，经过300 000次循环加载和1 000次5～55 ℃冷热循环后，再在力学测试机上测试试件的抗折强度，记录试件断裂时的力值和试件破坏形式。结果 B组和C组抗折强度显著高于A组（P＜0.05）。A组主要为不可修复性折裂，其他两组主要为可修复性折裂。结论±临床修复残根残冠时，可以优先考虑纤维桩加树脂核修复或者树脂充填修复。

Objective This study aims to compare the fracture resistance of teeth restored with different post and core systems by cyclic loading test and to predict long-term effects. Methods A total of 15 recently extracted mandibular premolars without crowns were endodontically treated. The teeth were randomly divided into three groups with five teeth in each group. Group A, teeth restored with cast metal post and core. Group B, teeth with fiber post and resin core. Group C, teeth with resin filling. All of the teeth were restored with full-cast metal crowns. The specimens were exposed to 300 000 cyclic loadings in a cyclic loading machine and 1 000 thermal cycles between 5 and 55 ℃. All of the samples were loaded in AG-IS mechanical testing machine with a compressive load until fracture occurred. The fracture load and the fracture mode of each tooth were recorded. Results The fracture resistance in group B and C were higher than that of the cast metal post and core restoration （P〈0.05）. Repairable fractures were observed in group B and C, whereas unrestorable and catastrophic fi＇actures were found in group A. Conclusion Fiber post and resin filling is a good choice to restore endodontically treated teeth.