论文部分内容阅读
目的 :采用三维有限元技术,分析下颌第一磨牙在面水平磨耗与倾斜磨耗2种情况下受力时,其牙体内的应力分布和瞬间位移情况,探讨近中根纵裂发生的生物力学依据。方法:运用Mimics有限元软件建立下颌第一恒磨牙三维有限元模型,分为无磨耗组(对照组)、水平磨耗组(实验组1)和倾斜磨耗组(实验组2)3组,实验组1和实验组2再根据4种磨耗程度,分别建立平切1、平切2、平切3、平切4和斜切5°、斜切10°、斜切15°与斜切20°8种研究模型。经面加载200 N的咬合力,运用MSC.Marc非线性有限元分析软件分析各种状态下模型内的等效应力和瞬间位移,分析牙根纵折发生的生物力学依据。结果:1无磨耗组第一磨牙应力主要集中在面中央窝沟处,位移等值线主要集中在牙冠近中偏颊面,向下延伸至牙颈部。2水平磨耗组应力主要集中于牙冠部及近远中根的根分叉水平,位移等值线整体逐渐偏向面近中偏颊侧牙颈部区域,类似于楔状缺损的V型。3在倾斜磨耗组,当磨耗平面向远中倾斜角度由5°增至15°时,瞬间位移等值线与牙长轴交角变小,近中根所受剪切力最大,产生的应力集中,发生牙根纵裂的可能性增大;当倾斜角度增大至20°时,应力主要集中在牙冠部,其位移等值线呈环形,最大位移出现在牙冠内。提示临床上当牙冠磨耗严重、牙尖斜面明显倾斜时,倾斜牙尖成为应力集中区,易发生折裂。结论:下颌第一磨牙面磨耗面向远中倾斜时,其近中根发生纵裂的可能性较大,为临床上预防性调磨过度磨耗的下颌第一磨牙,降低近中根纵裂的可能性提供了生物力学依据。
OBJECTIVE: To analyze the stress distribution and transient displacement of the mandibular first molar under the two conditions of horizontal wear and lean abrasion, and to investigate the biomechanical basis . Methods: The three-dimensional finite element model of mandibular first permanent molar was established by Mimics finite element software. The model was divided into three groups: wear-free group (control group), horizontal wear group (experimental group 1) and inclined wear group 1 and experimental group 2 and then according to the four kinds of wear degree, respectively, to establish a flat cut 1, cut 2, cut 3, cut 4 and bevel 5 °, bevel 10 °, bevel 15 ° and bevel 20 ° 8 Species research model. The occlusal force of 200 N was loaded on the face and MSC.Marc nonlinear finite element analysis software was used to analyze the equivalent stress and moment displacement in the model under various conditions to analyze the biomechanical basis of longitudinal root fracture. Results: The stress of the first molar in the wear-free group was mainly concentrated in the central fissure of the foramina. The displacement contours were mainly concentrated in the cheek surface of the crown, and extended down to the dental neck. The stress of horizontal wear group mainly focused on the level of root bifurcation of the crown and proximal and distal roots. The displacement contour gradually shifted towards the near mid-buccal side of the cervical area, similar to the V-shape of the wedge-shaped defect. 3 In the inclined wear group, when the inclination angle of the wear plane is far from the middle to the middle of 15 °, the instantaneous displacement isotropy becomes smaller with the long axis of the tooth, and the shear stress near the middle and middle roots is the largest, resulting in stress concentration, When the inclination angle increases to 20 °, the stress mainly concentrates in the crown, and the displacement contour is in the shape of a ring. The maximum displacement appears in the crown of the tooth. Tip clinically severe wear of the crown, cusp inclination was significantly inclined, inclined cusp as a stress concentration zone, prone to fracture. CONCLUSIONS: When the first mandibular molar facets are far-to-mid-inclined, there is a high possibility of longitudinal rupture of the proximal root. This is the first mandibular molar with preventive over-wear in clinical practice and reduces the possibility of near-middle root longitudinal rupture Biomechanical basis provided.