Temporomandibular Joint Remodeling During Mandibular Forward Positioning in Rabbits

Objectives: The Temporomandibular joint (TMJ), when submitted to mandibular forward positioning with functional appliances, have shown condylar and fossa remodeling, however, it has not been established whether this process remains constant over time. The purpose of this study was to determine the effect of a mandibular propulsion appliance on TMJ remodeling in growing rabbits at different time points.
Methods: The sample consisted of 32 ​​rabbits, five weeks old, randomly divided into four experimental and four control groups. Fixed acrylic bite-jumping appliances were fitted to the experimental animals to create continuous forward mandibular advancement, and animals were sacrificed after 30, 60, 90 and 120 days (n=4). The mandibular condyles and glenoid fossas were sectioned on the sagittal plane and stained with hematoxylin and eosin, Masson's trichrome and periodic acid-Schiff. Results for each animal were a mean of both TMJs. Groups were compared for each time point using the Mann-Whitney U test for the anterior and posterior regions of the TMJ.
Results: The results showed that newly formed bone was significantly increased in the experimental group in the anterior region of the mandibular condyle in all time points and in the anterior region of the glenoid fossa until 90 days. There was a significant increase in osteoblast proliferation, in the anterior region of the condyle at 30 and 120 days (p=0,029) and in the anterior region of the glenoid fossa at 30, 60 and 90 days (p=0,029). The posterior region of the TMJ showed significant bone resorption, at the condyle and glenoid fossa, at 30 and 60 days (p=0,029).
Conclusions: These results suggest that mandibular advancement caused by functional appliances promotes new bone formation in the anterior region and resorption in the posterior region of the TMJ, with greater activity during the first 30 days, although significant changes were still noticeable at the later time points.