牙本质壁厚度对原位牙倒预备微裂的影响

Effects of Remaining Dentine Thickness on Cracks of Root-end Preparation in Cadavers

目的:研究不同根尖牙本质壁厚度的尸体牙对超声倒预备微裂的影响。方法:36颗尸体前牙,暴露根尖约3mm,常规开髓,根管预备、冲洗、热牙胶充填后,沿垂直牙体长轴方向切除根尖3mm。中等功率下,采用金刚砂超声工作尖倒预备60s。剔除后按最薄剩余牙本质壁厚度2mm,1mm为界分为a、b、c 3组。染料结合体视显微镜观察根尖断面微裂。结果:微裂数量上3组差异有统计学意义,其中a、b之间差异无统计学意义,而c组明显多于a,b两组(P=0.010,P=0.018)。c组微裂多发生于洞壁最薄弱处,且以Ⅲ型居多,a、b两组差异无统计学意义。结论:剩余牙本质壁厚度对微裂的形成具有一定的影响,小于1mm后,微裂发生的频率和范围都明显增加,且容易发生在洞壁薄弱部位。

Objective：To evaluate the effects of remaining dentine thickness on cracks of root-end preparation in cadavers.Methods：36anterior teeth in situ in maxillary and mandibular jaws from cadavers were chosen,and 3mm of the root-end were exposed.All teeth were root canal prepared and filled,3mm of the root end were cut off.The root-end preparations were made using ultrasonic diamond tip for 60s,with 3mm depth.According to the thinnest remaining dentine thickness,which was 2mm and 1mm,all teeth were divided into 3groups named a,b,c group.2% methylene blue and stereoscopic microscope were used to observe the number and type of cracks.Results：There was significant difference among 3groups.Group 3provoked more number of cracks than the other two groups（P=0.010,P=0.018）,while the other two groups has no significant difference,TypeⅢcracks were most commonly observed in group 3,and they always happened among the thinnest dentine walls.However,there was no significant difference between group 1and 2.Conclusion：Residual dentine thickness has a certain influence on the formation of cracks.When less than 1mm,the frequency and range of cracks significantly increased,and they easily occured in the weak part of the dentine walls.