不同根管预备方法对无髓牙根管壁应力变化的影响

Analysis the Stress Variations of the Root Canal Wall of Pulpless Tooth by Different Root Canal Preparation with Finite-Element Method

目的分析用常规法根管预备和逐步后退法根管预备对无髓牙在咬合过程中根管壁应力变化的影响。方法在已建立下颌第一磨牙有限元模型的基础上,模拟常规法和逐步后退法修改模型并充填建立修改模型,运用特定的有限元分析软件,计算修改模型各部及3个根管管壁各部在垂直和侧向加载时的最大应力。结果2种修改模型的应力变化趋势相似,应力值在冠部几乎相同,在根部逐步后退法修改的模型的应力值略大于常规法修改的模型,3个根管中以近中颊根管壁的应力最大,远中根管壁的应力其次,近中舌根管壁的应力最小。修改模型与原始模型的应力变化亦相似。由于材料性质的改变,修改模型除在银汞合金处应力高于原始模型外,其它部位的应力值与原始模型接近或小于原始模型的应力值。结论无论常规法或逐步后退法根管预备都是安全有效的预备方法,临床医生可选择应用之。

Objective To analyze the stress variations of the root canal wall of pulpless tooth by different root canal preparations. Methods On the basis of the set up model of the mandibular first molar , modified model was established by simulation of the routine or step-back root canal preparation and filling in . Then the maximum mises stress of each part of teeth and wall of root canal were calculated by special finite-element software. Results The stress-changing tendency is similar between two modified models but the maximum mises stress of the model by step-back technique is a little greater than one by routine.The stress of wall of mesial-buccal root canal was the greatest and one of mesial-lingual root canal was the least at three root canals. The stress-changing tendency of modified models was similar to original model. The maximum mises stress of modified models was near or less than one of original model except that of amalgam layer because of material property alteration. Conclusion Not only routine but step-back technique is an effective and safe method.Dentist can choose them in practice.