不同洞缘角磨牙Ⅰ类洞复合树脂充填的应力分布

Stress distribution of composite resin filling in Class Ⅰ cavity of molars with different cavosurface angle

目的利用三维有限元分析不同洞缘角对磨牙面Ⅰ类洞复合树脂充填后应力分布的影响,为Ⅰ类洞形制备提供参考。方法建立3个洞缘角角度(A组90°、B组120°、C组135°)的下颌第一磨牙面Ⅰ类洞复合树脂充填的三维有限元模型,用热膨胀法模拟复合材料的聚合收缩,分析在聚合收缩和咬合载荷(600N)的共同作用下,修复模型在应力和位移分布方面的力学行为。结果窝洞尺寸相同的Ⅰ类洞,3种洞缘角度(其中B组、C组洞缘釉质斜面宽度为1 mm)的窝洞复合树脂修复后,A组修复模型总体及牙釉质的最大应力小于B组和C组修复模型总体及牙釉质的最大应力;3组牙本质和粘接剂的最大应力相近;C组复合树脂的最大应力最大,B组复合树脂的最大应力最小。从应力分布看,各修复模型中,最大应力主要集中在洞缘牙釉质、牙釉质-牙本质界面和修复材料边缘。结论复合树脂充填磨牙面Ⅰ类洞时,从减少剩余牙体组织应力的角度看,90°的洞缘角即无釉质斜面预备是一种较为理想的窝洞预备方式。

Objective To analyze the effect of different cavosurface angles on the stress distribution of ClassⅠcavity composite resin filling of molars through the three-dimensional finite element method and to provide references for the preparation of ClassⅠcavities.MethodsThree-dimensional finite element models of ClassⅠcomposite resin filling of mandibular first molars with three different cavosurface angles(group A:90°,group B:120°,group C:135°)were established.Polymerization shrinkage of composites was simulated with a thermal expansion approach.The mechanical behavior of the restored models in terms of stress and displacement distributions under the combined effects of polymerization shrinkage and occlusal load(600 N)was analyzed.ResultsFor ClassⅠcavities with the same cavity size,the total stress of the restoration model and the maximum stress of the enamel in group A were less than those in groups B and C after cavity composite resin restoration with three cavity cavosurface angles(in which the width of the enamel bevel was 1 mm in groups B and C).The maximum stress of the dentin and adhesive was similar in the three groups,the maximum stress of the composite in group C was the largest,and the maximum stress of the composite in group B was the smallest.In terms of stress distribution,the maximum stress in each restoration model was mainly concentrated in the enamel at the cavosurface,near the enamel-dentin interface and at the edge of the restoration material.ConclusionFrom the point of reducing the stress of residual tooth tissue,the preparation of 90°angle without enamel bevel is an ideal method for cavity preparation when composite resin is used to fill ClassⅠcavities of molars.