不同根管通路建立方式对根管治疗后的下颌第一磨牙应力分布的影响

Effect of different endodontics cavity accesses on stress distribution of endodontics treated mandibular first molars

目的利用三维有限元分析法评估不同根管通路建立方式对根管治疗后的下颌第一磨牙应力分布的影响。方法利用完整的下颌第一磨牙的Micro-CT的扫描数据建立4组有限元模型:完整天然牙模型(A组)、紧凑型根管通路模型(B组)、传统开髓方式不建立直线通路模型(C组)、传统开髓方式建立直线通路模型(D组)。B、C、D组在根管治疗后进行直接树脂充填。对以上模型施加4种不同静态压力,以计算和研究牙体组织应力分布及最大主应力值分布。结果受垂直向咀嚼力时应力峰值:C组>D组>B组>A组,受水平向咀嚼力时应力峰值:B组>A组>C组>D组,受斜向咀嚼力时的应力峰值:D组>B组>C组>A组,受最大咬合力时的应力峰值:C组>D组>A组>B组。除应力加载点,应力集中区主要位于颈周牙本质(pericervical dentin,PCD)。结论采用紧凑型根管通路的下颌第一磨牙较传统型开髓方式抗折裂能力强。保留PCD可能无法增加牙齿整体抗力,但有利于提升牙齿长期留存率。

Objective To evaluate the effect of different endodontic cavity accesses on stress distribution of endodontics treated mandibular first molars with a three-dimensional finite element analysis method.Methods With Micro-CT scans of an intact mandibular first molar,four finite element analysis models of mandibular first molars were designed and constructed:an intact teeth model(group A),a contracted endodontic cavity model(group B),a model traditional endodontic cavity without straight way established(group C),a traditional endodontic cavity model with straight way established(group D).Endodontics treated models were filled with gutta pertscha and then restored with resin.All models were subjected with four different forces.The stress distribution patterns and the maximum Von Mises(VM)stresses were calculated and compared.Results The peak VM stress with vertical force:C>D>B>A,the peak VM stress with horizontal force:B>A>C>D,the peak VM stress with 45°force:D>B>C>A,the peak VM stress of the largest bite force:C>D>A>B.Except the stress loading points,the stress concentration area was mainly located in pericervical dentin.Conclusion The resistance to fracture of endodontics treated mandibular first molars with contracted endodontic cavities is better than the traditional accesses.To preserve more PCD may not improve the resistance to fracture,but can be positive to improve the long-term retention.