Abstract
Recent studies have revealed that the biomechanical aspect of the temporomandibular joint has a critical influence on the occurence of temporomandibular joint disorders. Therefore, the configuration of joint components is expected to have a considerable effect on the displacement of the articular disk. The purpose of this investigation was to study the relationship between the disk displacement and the configuration of the condyle and the mandibular fossa. Out of 54 temporomandibular joints from Japanese cadavers aged 45 to 93 years, 18 joints without any gross sign of degenerative change were examined macroscopically. The 18 joints were divided into two groups according to their disk position, one group consisting of 10 normal joints and the other of 8 anteriorly diskdisplaced joints. The mean ages of the groups were 64.0 yrs, and 72.1 yrs respectively. The size of the condyle and the mandibular fossa, the angulation of the posterior slope of the eminence and the disk position were measured on the 3 sagittal sections, i.e, lateral, central, medial. In addition, sellanasion length was measured as a standard to estimate the relative joint size over the cranium size.
The following results were drawn:
1. No significant correlation was found between sella-nasion length and joint size.
2. The condyle of the anteriorly disk-displaced group was smaller than that of the normal group in the antero-posterior direction, whereas no difference was found between the two groups regarding the latero-medial condylar length.
3. The fossa of the anteriorly disk diplaced group was deeper and longer in the antero-posterior direction than that of the normal group. The anteriorly disk-displaced group had a larger angle of the posterior slope of the eminence. A significant correlation was found between the angle of the posterior slope of the eminence and the amount of the disk displacement in the lateral and central sagittal sections.
These results suggest that the condyle which has a small antero-posterior length and/or high and steep eminence has an increased risk of the articular disk slipping off the condyle.
