Shetty Bhavya, Khan Safiya Fatima, Irfana Khadijathul, Nambiar Manjusha
Department of Periodontology, Faculty of Dental Sciences, Ramaiah University of Applied Sciences, Bengaluru, Karnataka, India.
Al Wafa Dental Centre, Unayzah, Qassim, Saudi Arabia.
J Indian Soc Periodontol. 2024 Nov-Dec;28(6):691-696. doi: 10.4103/jisp.jisp_98_24. Epub 2025 Apr 3.
Finite element model (FEM) offers an ideal method for the accurate modeling of tooth periodontium with its complicated three-dimensional (3D) geometry. The present study aimed to assess periodontal ligament (PDL) stress under normal masticatory force in the mandibular second molar with and without osseous defect at two different angulations.
Cone-beam computed tomography was used to collect 3D information on the mandibular second molar. Four 3D models were designed using FEM. The first was a mandibular second molar with normal bone support. The second, third, and fourth models had three-wall defects where the mesial wall had bone loss up to 1/3, 2/3, and complete root length, respectively. Vertical and Oblique forces were applied to each model and statistical analysis was carried out using Von Mises stress analysis.
Von Mises stress on PDL was seen in the cervical area when the bone was lost up to one-third of root length. As bone loss increases, the stress is concentrated in the apical region and it increases with an increase in bone defect. Maximum PDL stress was 1.84 × 10 megapascal (MPa) under vertical force and 1.0 × 10 under oblique force. Maximum stress on cortical bone was 14.019 MPa under vertical force and 45.939 MPa under oblique force and the values were statistically significant.
Stress on PDL and cortical bone was four times higher under oblique force compared to vertical force. As periodontal support reduces, stress increases and gets concentrated on the apex, leading to apical extension of resorption. Teeth with compromised periodontium are more predisposed to occlusal trauma.
有限元模型（FEM）为精确模拟具有复杂三维（3D）几何结构的牙周组织提供了理想方法。本研究旨在评估在下颌第二磨牙存在和不存在骨缺损的情况下，在两种不同角度下正常咀嚼力作用下的牙周膜（PDL）应力。
采用锥形束计算机断层扫描收集下颌第二磨牙的三维信息。使用有限元模型设计了四个三维模型。第一个是具有正常骨支持的下颌第二磨牙。第二、第三和第四个模型有三壁缺损，其中近中壁的骨丢失分别达根长的1/3、2/3和完全根长。对每个模型施加垂直和斜向力，并使用冯·米塞斯应力分析进行统计分析。
当骨丢失达根长的三分之一时，在颈部区域可见牙周膜上的冯·米塞斯应力。随着骨丢失增加，应力集中在根尖区域，且随骨缺损增加而增加。在垂直力作用下，牙周膜最大应力为1.84×10兆帕（MPa），在斜向力作用下为1.0×10。皮质骨在垂直力作用下的最大应力为14.019 MPa，在斜向力作用下为45.939 MPa，这些值具有统计学意义。
与垂直力相比，斜向力作用下牙周膜和皮质骨的应力高出四倍。随着牙周支持减少，应力增加并集中在根尖，导致吸收向根尖延伸。牙周组织受损的牙齿更容易发生咬合创伤。
