Three-dimensional Stress Analysis Of The Periodontal Ligaments Of Cantilever Fixed Bridge Abutment Under Dynamic Loads By Finite Element Method

ObjectiveA three-dimensional finite element model of a human mandibular molar cantilever fixed bridge has been established to investigate stress and displacement distributions of periodontal ligament of abutments under transient dynamic loads so as to provide theoretical references of biomechanics for clinical application of cantilever fixed bridge.MethodsA normal human mandible was used as an anatomy foundation to build a three-dimensional finite element model of mandibular molar cantilever fixed bridge and the corresponding periodontal substance with CT scanning aided model building,AutoCAD software and ANSYS software.Finite element analysis was performed on the model under dynamic loads in various directions and positions in a circle of mastication.The stress and displacement distributions and stress-time curves were analyzed to study the biomechanical behavior of periodontal ligament of abutments.Results1 The constructed model has a good similarity to the morphology of the three-dimensional images.The model can be rotated,zoomed in or zoomed out arbitrarily.It can also be viewed in perspective or cut apart.The model can serve for the needs of the three-dimensional stress analysis.2 With loading and unloading time accumulating,the stress values of periodontal ligaments for「56 increase gradually whichever positions dynamic loads are applied to.During the oblique direction,the stress reaches a peak value of a mastication cycle.There is little residual stress at the end of unloading time. 3 Under the same loads,the capabilities of both compressive resistance and anti-tensile strength for「5 periodontal ligament are weaker than that for「6 periodontal ligament.4 After the fixed prosthodontics,the maximum stress values almost concentrate on the periodontal ligament of the abutment nearest to the pontic.5 After the fixed prosthodontics,the periodontal ligaments of the abutments are mainly under compressive stress,while those of「5 gradually display obvious tensile stress following the displacement of load points to distance.6 The maximum values of compressive stress,tensile stress and Von Mises stress in the periodontal ligaments focus on the cervical margin.7 In the continuous mastication cycles,stress values of the latter cycle are larger than the former for the abutments periodontal ligaments,but increments appear slight.Conclusions1 Obtaining the image of the teeth and periodontal tissues by CT scanning technique,and establishing the model with AutoCAD computer image processing system and ANSYS three-dimensional finite element software is an accurate,effective and reliable method.2 There is some level of residual stress in periodontal ligaments after one mastication circle.3 In the mastication movement,the oblique loads affect the periodontal health most.4 The requirements for conditions of the periodontal ligament of the abutment nearest to the pontic are much higher than those of other abutment.5 Within the continuous mastication cycles,the stress cumulation will not injure the periodontal ligaments.