FE models

The FE models in this study were based on those reported by Kasai et al. The material properties of the soft tissues such as the PDL and the TMJ, which were mainly deformed in the analysis, were considered to be crucial, because the aim of this study was to investigate the distribution of occlusal forces on the teeth, implants, and TMJs. In Figs. 3 and 8, the PDLs of anterior teeth and the springs corresponding to opposing teeth show two-stage displaceability as reported previously and were considered to be appropriate. The load-displacement curve of the springs corresponding to TMJs was assumed to be similar to that of the cartilage because of its far smaller elastic modulus than that of the TMJ disc. Therefore, the elastic modulus of the springs corresponding to TMJs was determined based on the thicknesses of the TMJ disc and articular cartilage, the stress-strain curve of the intervertebral discs, and the displacement of the condyle in intercuspal clenching by indirect measurement. Although the material properties of human body depend on the individual, the models in this study were therefore considered to be appropriate to investigate the distribution of occlusal forces on the teeth, implants, and TMJs.

The meaning of “occlusal adjustment” in this study

In the FE model before loading, there is no stress or deformation anywhere in the model with perfect even occlusal contact. However, this situation cannot really occur because of the existence of some occlusal load in the intercuspal position (ICP). Since the displaceability of dental implants is quite different from that of the natural teeth and TMJ, the distribution of the occlusal force exerted on the occlusal surface of natural teeth and superstructures depends on the amount of the occlusal load, i.e., the contractile force of the musculature.