根管预备程度对无髓牙根管壁应力影响的分析

目的 分析不同根管腔的直径对根管壁应力的影响。方法 在已建立的下颌第一磨牙模拟常规法根管预备修改的实验模型基础上，再修改根管腔直径，使根管直径扩大到牙根直径的1／3和1／2，并在修改模型上加载，计算在不同加载条件下牙齿各部及管壁的最大应力。结果 根管腔直径增大会引起根管壁应力的升高，该变化主要出现在根管口和根上1／3段，侧向加载时产生的应力差异大于垂直加载时产生的应力差异。结论 根管预备应以去除根管壁的感染物质，获得良好的根管成形为原则，过度的预备不仅没有必要，甚至有害。

Analysis the Effect on the Stress of Root Canal Wall of Pulpless Teeth by Different Degree of Root Canal Preparation

Objective To analyze the stress variations of wall of root canal of pulpless teeth that resulted from different diameters of root canal.Methods On the basis of the finite-element model of the mandibular first molar that modified by routine,diameter of root canal was modified and enlarged so as to the diameter of root canal was1/3and1/2of root diameter,then modified models were loaded and the maximal stress of each part of teeth and wall of root canal was calculated.Results The results revealed that enlargement of root canal diameter will bring on increase of stress of root canal wall at the orifice and coronal1/3.The stress difference of lateral loading was greater than that of vertical loading.Conclution The principle of root canal preparation should be infected material removed and good shape of root canal gained.Over-preparation is unnecessary and harmful.