Factors affecting degeneration in human temporomandibular joints as assessed histologically

The influence of sex, age, tooth loss, and articular disc position on temporomandibular joint (TMJ) degeneration was evaluated in specimens collected at autopsy from 15 women and 38 men ranging in age from 15 to 92 yr. The position of the articular discs was classified as normal or abnormal, tooth loss was both counted and categorized. Degenerative changes of the articular tissues were assessed histologically and quantified, taking into account both the severity of structural alterations and their extension along the articular surface. This was recorded separately in the condyle, disc, and temporal component, three latero-medial joint regions, and putative load-bearing and non-load-bearing surfaces. Analysis of covariance with repeated measures served for testing contributing factors. It showed that the effects of sex and the number of missing teeth were insignificant, whereas age up to about 55-60 yr and reduction of dental arch length proved to be the most important factors. Load-bearing seemed to play a significant role mainly at younger ages, and the effect of disc position was significant, when internal derangement was combined with reduction of dental arch length. Thus, rising severity of TMJ degenerative changes appears to be associated primarily with increasing age. In addition, it may also depend on mechanical factors, in particular loss of molar support and, to a minor degree, abnormal disc position.