Alterations of the rat temporomandibular joint in functional posterior displacement of the mandible.

Functional malocclusion that induces posterior condylar displacement may affect the remodeling processes of the temporomandibular joint structures. We tested the hypothesis that intermittent posterior condylar displacement due to functional malocclusion traumatizes condylar cartilage and joint innervated nerve fibers. Thirty-nine eight-week-old Wistar rats were used. To induce functional posterior condylar displacement, guiding appliances were attached to maxillary incisors of 24 rats for four, seven, and 14 days. Fifteen normal rats served as controls. Sections were stained with hematoxylin and eosin or processed for immunohistochemistry of protein gene product 9.5 and growth-associated protein-43 (GAP-43). Functional posterior condylar displacement led to a diminution in proliferative cells, reduction in cartilage width, and re-expression of GAP-43-immunoreactive nerve fibers. These results indicate that intermittent posterior condylar displacement due to functional malocclusion causes dysfunctional remodeling of condylar cartilage and nerve injury.