Experimentally induced unilateral tooth loss: expression of type II collagen in temporomandibular joint cartilage

We sought to examine possible changes in pattern and concentration of type II collagen in the condylar cartilage and articular disc of the temporomandibular joint (TMJ) in response to unilateral extraction of mandibular teeth in a rabbit model as a means of elucidating the effects of unilateral mastication on the TMJ.

A total of 12 experimental rabbits were killed either 3 or 6 weeks after the extractions, and 3 additional rabbits without extractions were used as controls. TMJ blocks from both sides of each of the 15 animals were examined for type II collagen via an immunoperoxidase procedure.

Anti-type II collagen antibody (Ab) binding was detected mainly in the hypertrophic chondroblast layer of the condylar cartilage of normal rabbits. At 3 weeks after unilateral extraction of teeth, anti-type II collagen Ab binding to the territorial matrix of the hypertrophic chondroblast layer of the condylar cartilage and to the disc was stronger than normal. The increase in Ab binding appeared more dramatic on the nonfunctional side than on the functional side of TMJ. Variations from the normal pattern of anti-type II collagen Ab binding in terms of distribution through the extracellular matrix and fibrillar appearance were also observed.

The findings suggest that the condylar cartilage and disc adapt to the imbalance induced by unilateral extraction of teeth through chondrocyte repair responses involving collagen II expression that appear to differ between the functional and nonfunctional sides of the TMJ.