Three-dimensional finite element analysis on the effects of partial anodontia and its restoration to the stress distribution in temporomandibular joint

Objectives: To investigate the effects of teeth apical stress changes caused by teeth missing and its restoration on the temporomandibular joint (TMJ) stresses. Materials and Methods: The apical stresses measured from photo-elastic experiments (2Kg centric vertical loading to different kinds of occlusion separately) were applied to the established three-dimension finite elemental model. The stress distribution on condyle, superfacial cartilage and TMJ disc were compared. Results: 1. The stress on both of the anterior surface of condyle and its superfacial cartilage and on the intermediate band of disc were mainly compressive, while the stress on both of the posterior surface of condyle and its superfacial cartilage and on the posterior band of disc were mainly tensile. 2. Anterior teeth missing, anterior teeth and bilateral premolars missing and posterior teeth missing all could cause the distinct changes of magnitude and distribution of TMJ stresses. However, the changes could be effectively reversed by the restoration of missing teeth. Conclusions: Changes of apical main stress resulted from partial anodontia during centric biting would affect TMJ stress quantitatively, which could probably result in the temporomandibular disorders, so the timely restoration is necessary.