牙体预备形态对烤瓷贴面复合体抗折强度及断裂模式的影响

目的比较三种牙体预备方法对烤瓷贴面复合体（PVCs）抗折强度及断裂模式的影响。方法分别对离体上颌中切牙进行3种形态（I型、L型、U型）牙体预备，制作长石质烤瓷贴面，树脂黏接剂黏接．用MTS力学实验机测试各牙的断裂载荷值，记录瓷贴面的断裂频数，数据作统计学分析。结果I、L、U三型牙体预备的PVCs与天然牙对照组的断裂载荷值分别为278．61±73．86N（n=9）．295．17±71．76N（n=9），303．42±96．87N（n=8），332．29±60．06N（n=10），经统计学分析四组间断裂载荷值及瓷贴面的断裂模式差别无统计学意义（P〉0．05），3组实验组与对照组的牙体断裂模式差异有统计学意义（P〈0．05）。结论在正中牙合]瓷贴面间接受力的条件下，采用3种牙体预备设计的PVCs均具有良好的的抗折性能．但烤瓷贴面修复改变了牙体组织在加载条件下的力学特性。

Influence of three types of tooth preparation methods on fracture load and mode of porcelain veneers comples

Objective To investigate the effects of three types of tooth preparation methods on fracture load and mode of fired porcelain veneer complexes （PVCs）. Methods Human maxillary central incisors were collected and randomly divided into four groups. In the first three groups, teeth were prepared according to the three recommend tooth preparation methods （Type I, Type L, and Type U） respectively. Prepared teeth were restored with fired porcelain veneers, then bonded with adhesive resin luting system. 10 teeth were remained intact and used as controlled group. Fracture loads were recorded with a mechanical testing machine. Statistical analysis was made with SPSS for Windows. Results Mean fracture loads in groups of Type I, L, U and the control group were as follows： 278.61N ± 73.86N（n=9）,295.17N ± 71.76N （n=9）,303.42N ± 96.87N （n=8）,332.29N ± 60.06N（n= 10）. No significant difference was found among the fracture loads of the three PVC groups and the controlled group （P 〉 0.05 ）, but there was significant difference in the tooth fracture mode among the three PVC groups and the controlled group （P 〈 0.05）. Conclusions When loading point is located in tooth structure, the fracture resistance of PVCs with all the three types of tooth preparations are comparable to the natural teeth. Fired porcelain veneer can change the biomechanical behavior of the nature tooth.