A Dynamic Finite Element Analysis Of Stress Distribution In The Supporting Bone Of Mandibular Molar Fixed Bridge Abutment

ObjectiveThis study used the finite element method(FEM) to analyze the stresses induced in the supporting bone tissue of the fixed bridge abutment in the mandible under transient dynamic loads,so as to provide theoretical references of biomechanics for clinical application of the fixed bridge.MethodsA three-dimensional finite element model simulated a 3-unit mandibular molar fixed bridge and corresponding periodontal substance with computed tomography(CT) scan images and constructed in 3-D computer-aided design(CAD) software and ANSYS software.In the model,the second premolar,and second molar served as abutments.A supporting periodontal ligament and alveolar bone(cortical and trabecular) were modeled.Finite element analysis was performed on the model under dynamic loads in various directions and positions in a masticating cycle.The stress and stress-time curves were analyzed to study the biomechanical behavior of supporting bone of abutments.Results1 The constructed model has a good similarity to the morphology of the three-dimensional images,which could serve for the needs of the three-dimensional stress analysis.2 before the fixed bridge was applied,the stress was concentrated on the cervical of cortical bone under different loads.But after the fixed bridge applied,it spreaded to the cancellous bone better.3 When loading on(?)567 of the bridge model,after lingual loading,the maximum Von Mises value of the lingual cortical bone around(?)5 was 3 times that after vertical loading, while the one around(?)7 was 1.5 times.After buccal loading,the maximum Von Mises value of the buccal cortical bone around(?)5 was 1.4 times that after vertical loading,while the one around(?)7 was 1.2 times.4 Under oblique loads,the stress concentration was more obvious than that under vertical loads.5 When loading on(?)57 of the non-bridge model,the maximum Von Mises value of the cortical bone around(?)5 was much higher than that around(?)7 in the same loading period. While loading on(?)57 of the bridge model,the differential value of the maximum decreased, especially in the oblique loading period.6 In a masticating cycle,the occurrence times of the peak value of different parts were arranged in order(early to late):cervical,cancellous bone,and root.At 0.875s,the stress value of all parts were more than zero.Conclusion1 CT scanning aided finite element model building,with Auto CAD software and ANSYS software,is a practical and feasible method.2 The stress of the supporting bone of the fixed bridge abutment is concentrated in the cervical of the bone.3 The change of the loading direction affects the value and distribution of stress in the supporting bone,oblique loads tends to produce more stress concentration than vertical loads.4 Thanks to the rigid fixed bridge,the pontic reassigns occusal force.The stress of supporting bone is more even-distributed.5 Value and distribution of stress in supporting bone are time dependent.After a masticating cycle,there is residual stress in supporting bone.