Morphologic changes in the TMJ following splint wear.

Intraoral splints are a commonly used dental treatment for a variety of conditions. Because such splints alter the condyle-disc-fossa relationship, they probably change the loading status of the temporomandibular joint (TMJ), including the TMJ disc. Collagen, a major constituent of the disc, acts to resist tensile loading, and it is presumed that the fiber orientations of the individual disc bands reflect their functional loading. Therefore, the purpose of this study was to examine effects of intraoral splint wear on TMJ morphology in general, and collagen orientation of the intra-articular disc in particular. Young adult, female miniature pigs were divided into three groups: open-bite splint, protrusive-bite splint, and unsplinted control. Splints were worn for 2 months, after which the TMJ discs were harvested for histological examination and stereological analysis, and the skulls were cleaned. Although the splints had no effect on skull dimensions, changes were seen in the TMJs. The discs of the protrusively-splinted group showed an increased thickness of the posterior band (P < 0.015) and minor changes in collagen orientation of the anterior band. The most striking change was the presence of a degenerative osseous defect on the medial side of the mandibular condyle in half of the splinted animals. These results indicate that prolonged splint wear can induce remodeling and even injury of TMJ tissues.