不同根管预备方法对根管应力大小和分布影响的三维有限元分析

摘要

AIM: To analyze the effect of different root canal preparation techniques on the root canal stressrnvalues and distribution, and to compare the stress change under the different loading. METHODS:30 extracted human mandibular premolars were randomly divided into 3 groups ( n = 10). The root canals were prepared with standard system using Ni-Ti Mtwo instrument ( G1) , crown-down technique using Ni-Ti Protaper instrument (G2) and step-back technique using conventional stainless steel K-files (G3) respectively. The prepared canals were then filled with warmhearted gutta pertscha and restored with composite resin. CT scan and Abaqus 6. 10 software were used to establish 3D finite element models. The stress magnitude and distribution of the models were analyzed under the loading of 150 N vertically and at 45° linguoclination respectively. RESULTS: After root canal preparation, high stress area was mainly concentrated in the crown 1/3 of the canals, the stress value decreased gradually from the root canal orifice to the apical foramen. The average peak root canal stress under lateral loading was significantly higher than that under vertical loading(P<0.05) in all the groups. In the crown 1/3 and middle 1/3 of the canals under both loading patterns the stress values were not statisticantlly different between group Gl and G2 ( P > 0. 05 ) , but the stress of G3 was higher than that of Gl and G2 (P < 0. 05). In the apical foramen 1/3 of the canals under both loading patterns the stress values were not statisticantlly different among the groups(P >0. 05). CONCLUSION: All three root canal preparation methods were safe and feasible. Preparation with Protaper and Mtwo nickel titanium may result in more balanced root canal stress distribution.%目的:研究不同根管预备方法对根管应力大小和分布的影响,并比较不同加载状态下根管应力的改变.方法:选取30个离体下颌第一前磨牙,随机分成3组(n=10)∶G1组(标准法)用镍钛器械Mtwo预备；G2组(冠向下法)用镍钛器械Protaper预备；G3组(逐步后退法)用不锈钢K锉预备.预备后的根管经热牙胶充填和复合树脂修复后,应用CB-CT技术与Abaqus 6.10软件等相结合建立各组牙齿三维有限元模型,分析比较模型在垂直和舌侧倾斜45°不同载荷条件下的应力大小和分布情况,载荷量为150 N.结果:根管预备后高应力区主要集中在根管冠1/3,应力值从根管口到根尖逐渐减小.同一组内各部位侧向加载时的应力峰值均明显高于垂直加载(P＜0.05).在根管冠1/3和中1/3区域,两种加载情况下G1组与G2组应力峰值差异无统计学意义(P＞0.05),G3组应力大于G1组、G2组(P＜0.05).在根尖1/3区域两种加载情况下各组间差异均无统计学意义(P＞0.05).结论:3种根管预备方法均安全可行,其中Protaper和Mtwo组根管应力分布更加均衡.