The effect of physiological nonbalanced occlusion on the thickness of the temporomandibular joint disc: A pilot autopsy study

Statement of problem. The temporomandibular joint (TMJ) disc is often observed to be thicker in temporomandibular disorder (TMD) patients. This clinical observation requires verification. Purpose. The purpose of this pilot study was to investigate whether the TMJ disc responds to dysfunctional occlusal changes by an increase in thickness. Material and methods. Twelve cadaver heads were divided into 2 groups, I with physiologically balanced occlusion (BO), 7 cadaver heads and 14 joints, and the other with physiologically nonbalanced occlusion (NO), 5 cadaver heads and 9 joints. The NO group had defining traits, such as reverse articulation or tightly locked occlusion. The latter is an occlusal relationship with drifted, tilted, and/or supraerupted teeth, often seen in patients who have lost posterior teeth. Histological sections from the lateral, center, and medial parts of the joints stained with haematoxylin and eosin were used for measuring the disc thickness. Student t tests and Bonferroni correction were used to compare groups (alpha=.05). Results. All 9 mean thickness values were higher in the NO than in the BO group. According to the t tests, the postenor band was thicker in the lateral (P=.007) and center (P=.015) sections, and the intermediate zone was thicker in the lateral section (P=.008) in the NO than in the BO group. These differences were not significant after Bonferroni corrections. Conclusions. The results suggest that the TMJ disc has the ability to adapt to alteration of the space between condyle and fossa caused by occlusal changes. Further studies from larger groups should be undertaken.