【作者】 袁理； 岳林； 王嘉德；

【Author】 YUAN Li, YUE Lin. WANG Jia-de.(Department of Cariology, Operative Dentistry and Endodontics, School of Stomatology, Peking University. Beijing 100081, China)

【机构】 北京大学口腔医学院牙体牙髓科；

【摘要】 目的:探讨不锈钢K锉断裂机理,分析根管锉在弯曲和扭转条件下的应力分布。方法:采用扫描电镜观察不锈钢K锉断口。运用ANSYS9．0三维有限元分析软件建立不锈钢K锉的三维有限元模型,计算其在弯曲和扭转条件下的应力分布。结果: ①不锈钢K锉的断口呈现脆性断裂与韧性断裂并存的特点;②建立了0．02锥度20#不锈钢K型根管锉三维有限元模型;③在弯曲条件相同的情况下,点接触的应力集中于切割刃口,边接触的应力集中于切割刃之间的沟槽中;④顺螺纹扭转时,拉应力分布在切割刃口上;逆螺纹扭转时,拉应力分布在切割刃之间的沟槽中。结论:①不锈刑K锉断裂机理为金属疲劳,以脆性断裂特征为主;②最大拉应力值产生在器械表面,不同弯曲方式和扭转方式造成的应力集中部位不同,由此形成的断裂起点位置不同。更多还原

【Abstract】 PURPOSE: To investigate the fracture mechanisms of stainless steel K (SSK)files and analyze the stress distribution under curved and torsional conditions. METHODS: 3 clinically fractured SSK files were observed under SEM. A 3-dimensional finite element model was established and analyzed under curved and torsional conditions by ANSYS9.0. RESULTS: (1)The fracture surface of SSK files showed characteristics of both fragile and ductile mechanisms. (2)A finite element model of a 0.02 taper SSK20# file was established. (3)Under curved conditions, the stress was focused on the cutting edge when point contact occurred or between the neighbored cutting edges when line contact occurred. (4)The stress was focused on the cutting edge when SSK file was turned counterclockwise or between the neighbored cutting edges when it was turned clockwise. CONCLUSIONS: (1)The fracture mechanisms of SSK file is metal fatigue, mostly present fragile fracture. (2)the Max pulling stress was focused on the surface of the file. In different motion conditions, the stress might be focused on different positions which might lead to fracture.更多还原