The effect of occlusal loss on normal and pathological temporomandibular joints: an animal study.

The effect of unilateral posterior malocclusion on temporomandibular joint intra-articular pathology was studied in sheep. In Group I, osteoarthritic changes were induced in the left temporomandibular joint by gentle scraping of the articular surface (Ishimaru and Goss, 1992). Group II had the same procedures as Group I, with concurrent extraction of all the left maxillary posterior teeth. Group III had a different osteoarthritic precondition in the left temporomandibular joint, allowing synovial fluid to contact the condylar marrow (Ishimaru et al., 1992). Group IV had the same procedure as Group III, with concurrent extraction of all the left maxillary posterior teeth. Group V had unilateral maxillary molar teeth extraction in the left side. At 3 months, the animals were sacrificed and the joints examined histologically. There were no significant differences between normal control joints and those with unilateral tooth extraction (Group V). Similarly the degree of osteoarthritic change was the same between Groups I and II. Significant differences (p < 0.05) were seen between Groups III and IV with tooth extraction increasing the osteoarthritic effects. Hence it was concluded that in sheep, malocclusion had no effect on the normal temporomandibular joint and on one type of experimental osteoarthritis, but accelerated osteoarthritic change in another model.