ABSTRACT
In order to study the stress distribution and displacement characternstic of the temporomandibular joint (TMJ) during centric occlusion, using the three dimensional nonlinear finite element model of normal human TMJ developed from in vivo with simulation of the contact relationship within TMJ, the stress and the maximum displacement of various structures in the TMJ were calculated and analyzed during centric occlusion. Furthermore, we separately accounted the mechanical properties of various structures in human TMJ and three dimensional muscle force vectors of their masticatory muscles measured and analyzed by use of the fusion of cranio jaw facial CT and MR image with the multiresolution method based on wavelet pyramid. The results showed that there were significant differences in the region and value of stress distribution on the surface of the disc, condyle and articular fossa during centric occlusion, in which the biggest stress was distributed in the condyle, the second in the articular fossa, and the smallest in the disc. During centric occlusion, the disc, condyle and articular fossa moved upperly, posteriorly and medially with the biggest displacement on the condyle, the secondary one on the disc and the smallest one on the fossa. It suggested that it is clinically feasible to systematically and rationally calculate and analyze the stress distribution and displacement character, and the results were satisfying
ABSTRACT
Purpose: To analyze the effect of the intraarticufar contact of the temporomandibular joint ( TMJ ) on three dimensional nonlinear simulation of human TMJ forces in order to simulate the distribution and transfer of TMJ forces more realistically and logically. Materials and Methods: Combining helical CT scanning technology with three dimensional finite element method, together with Auto CAD software, three dimensional nonlinear finite element models were developed in vivo for comparison with the changes in the stress within the TMJ in different contact conditions. Results: The stresses on the surfaces of articular disc and condyle in the finite element models with contact elements between the disc and condyle were mainly distributed on their anterior and medial regions, and the stresses on other regions were relatively smaller. But, the stresses of those models without contact element were mainly distributed on their midposterior and medial aspacts. Moreover, the stress values were higher. When the friction coefficient was in the range of 0 0.15, the distribution extent and magnitude of the contact stress between the disc and the condyle in the TMJ were completely same. Meanwhile, the surface stresses on the disc and the condyle were nearly coincident in three ways of disc condyle contact, which were no friction contact, rigid contact and elastic contact. Conclusion: In the issue of disc condyle contact of simulating TMJ forces with three dimensional nonlinear method, the stress distribution in the joint with complete contact relationship between the disc and the condyle conforms more to the physiological condition. The lower friction coefficient ( 0 0.15 ) in the TMJ and various contact patterns between the disc and condyle had no evident influence on the stress distribution in the TMJ. Three dimensional nonlinear analysis for the forces in the TMJ might be more realistic and reasonable because of contact simulation among various structures within the TMJ.