Title: Malocclusion on the Histology of the TMJ Cartilage of Rats
Xinyun Liu (Presenter)
University of Pittsburgh
Wuyang Li, University of Pittsburgh
Michael Gold, University of Pittsburgh
Alejandro Almarza, University of Pittsburgh
Objectives: We have previously demonstrated that a change in temporomandibular joint (TMJ) loading associated with unilateral splint placement over a maxillary arch is sufficient to drive degeneration of the mandibular condyle in the rabbit. Because of the variety of validated assays of orofacial nociception available in the rat, the objective of the present study was to determine whether it was possible to adapt the splint model of TMJ disorder (TMJD) developed in the rabbit, to the rat.
Methods: Resin bite-raising splints (around 1mm) were applied unilaterally to the maxillary molars of 5-month-old male Sprague-Dawley rats (n=4). After 4 weeks, all the rats were euthanized and histological analysis of the TMJ was carried out on both splinted and contralateral sides of the jaw with Hematoxylin & Eosin (H&E), safranin O, Masson’s trichrome, and Picrosirius red staining.
Results: Primary tissue boundaries were detectable on the condyles ipsi- and contr-lateral to the splint placement. These included the fibrous zone, proliferation zone, mature zone, hypertrophic zone and subchondral bone (Figure 1A). However, except for the faint staining around the pericellular area, there was no staining for glycosaminoglycans (GAG) in the cartilage layer (Figure 1B). Collagen was widely stained throughout the condyle (Figure 1C, D).
Conclusions: The absence of GAG staining in the condyle is consistent with the presence of joint degeneration. The bilateral nature of the change suggests the impact of a unilateral splint is bi-lateral. In addition to sham controls, it will be important to further characterize to time course of both the onset and recovery of the changes in the joint and determine the extent to which the histological changes correlate with changes in joint sensitivity.