The Effects of PDL Simulations for a Mandibular Premolar FEM Model

• Main Authors: Yao-Ning Lei, 雷曜寧
• Other Authors: Chau-Hsiang Wang
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/13768484022587862692

碩士 === 高雄醫學大學 === 牙醫學研究所碩士班 === 93 === In times, the numerical techniques of the finite element method (FEM) are more and more destined to simulate stress distribution induced by occlusal force systems. Unfortunately, there are still not definitive principles for model construction of periodontal ligament by finite element method. This study, adopting a standardized model, undertook finite element analysis to explore the stress distribution situation when a single lower first premolar with various periodontal ligament thicknesses was putted under occlusal force; the results can be applied for further FEA models and a clinical reference. A lower first premolar of standard model was embedded in the transparent resin and cut into thin slices. The slices were scanned onto the computer to obtain an image of accurate dimension and outline. The outline was then subdivided into new geometrical key points. Entering the theses key points into CAE software (ANSYS 5.6, ANSYS Inc in order. USA) produced sets of significant data including lines, surfaces and volumes, thus ultimately created a solid model. The whole model was presumed to be an isotropic and homogeneous material with various thicknesses. The models simulated the periodontal ligament thickness of approximately 0 mm, 0.25 mm, 0.5 mm, and 0.75 mm. Another model is also constructed to simulate the PDL of physically uneven thickness with a proportion of 2:1:3 ( 0.5 mm at cervical third, 0.25 mm at middle third and 0.75 mm at apical third of the root ). It was then placed in a cubic block simulating a tooth in a schematic alveolar bone surrounding. Vertical and horizontal forces of 170 N were separately applied on the tooth. The stress distributions on root, bone and periodontal ligament were then observed. The results for the PDL of various thicknesses are more similar to each other than to those without any PDL. The PDL plays a role of stress distributor, redirecting the stress throughout the whole tooth i.e. crown to root and the surrounding tissue. It also decreases the stress on crestal bone. The model with proportionally varied thickness reveals more reasonable distribution pattern than that with even thickness. But it can’t be confirmed if the simulated stress distributions approach the actual situation by the result. The necessary data about periodontal ligament orientations, distributions, mechanical properties, and how they change during loading and function, are not available. It may be more prudent to add nothing into the FEA model than to include an imprecisely simulated one.