Kinematic Analysis of the Rabbit Temporomandibular Joint after Altered Occlusion

Objectives: Up to 11% of individuals with temporomandibular joint (TMJ) disorders have symptoms of TMJ osteoarthritis (OA), where pain is the primary complaint associated with the loss of function. To explore the mechanistic underpinnings of TMJ-OA, we developed a rabbit TMJ-OA model where 6 weeks of splinting was sufficient to drive an almost complete loss of the subchondral layer of the fibrocartilage covering the condyle. The objective of this study was to determine the effects of this altered occlusion from splinting on TMJ kinematics in the rabbit.
Methods: Skeletally mature, female, New Zealand White rabbits were fitted with 1 mm dental splints (n=3) to mechanically alter occlusion. Three-dimensional skeletal kinematics via bi-axial x-rays was used to assess TMJ motion before and after 6 weeks of splint placement.
Results: An overall decrease in the range of joint movement was observed in the joint space between the condyle and fossa. The total magnitude of the maximum distance between the points on the condyle and fossa decreased from 3.6±0.8 mm to 3.1±0.6 mm for the working condyle and from 2.8±0.4 mm to 2.5±0.4 mm for the balancing condyle (p<0.05). The anterior-posterior displacement decreased by 21% and the superior-inferior by 9% for the working condyle and for the balancing condyle the displacements decreased by 15% and 14%, respectively.
Conclusions: Results of these experiments suggest a relationship between altered TMJ kinematics, fibrocartilage damage and TMJ pain. They may provide guidance to surgeons on the window in which interventions to normalize malocclusion associated with trauma may be most successful.