Studies On Mechanical Behavior And Remodeling Process Of Mandible And TMJ Under Orthopedic Force

Stress-related temporomandibular joint (TMJ) disorders and morphologic change of mandible appear in the orthopedic treatment of prognathism with chinup. So biomechanical components such as the stress or strain from orthopedic force should be studied to further explore the association with morphologic change in the mandible. Thus stress distribution in the TMJ and mandible should be investigated during the therapy of chinup therapy. First, the transverse section of the mandible of volunteer was scanned by means of Computerized tomography (CT) . the scanned pictures was stored and transformed in computer. According to the relationship between the pixels of the picture and the size of the actual mandible, a three-dimensional geometric model of the mandible including the TMJ is developed with the scanned pictures. Then A chin up force of 6.37 N was applied to investigate the stress distribution on the surface of condyle. It is shown that compressive stress is distributed in the posterior and lateral area of condylar surface, while tensile stress in the anterior and medial part. It is also shown stress is high along the line of genial angle and two other areas .In this thesis, a new and simple model based on Cowin's is proposed and normal isotropic remodeling process of bone surface is simulated with the help of available FEM software. New elements are created and new remodeling model is developed. Then the strain distribution in the new model is compared with that of the original model and the effect of normal remodeling is analyzed with the conclusion that normal remodeling enable bone tissue to reduce both the strain and gradient of the strain. Another remodeling FEM model is developed in the same way to simulate anisotropic normal remodeling process including mass change. And come to like conclusion that the strain is more effectively reduced during anisotropic remodeling.The conclusion is consistent with the proposition that bone tissue is a sort of self-adaptive material and can change its geometrical and mechanical properties to avoid damage from external load.