Objectives: To histologically and immunohistochemically assess the pattern of expression of bone morphogenic proteins 2 and 4 (BMP2/4) and proliferating cell nuclear antigen (PCNA) in response to bite jumping appliances in the condylar cartilage and the glenoid fossa. Materials and Methods: Fifty-five 4-week-old female Sprague-Dawley rats were randomly divided into four experimental and four control groups. Bite-jumping appliances were fitted to the experimental animals. The rats were sacrificed at 3, 14, 21, and 30 days, and the temporomandibular structures were analyzed histologically and immunohistochemically. Results: The expression of BMP2/4 in response to bite-jumping appliances was statistically significant in the condylar cartilage and the glenoid fossa. Cell proliferation was not significant. Conclusion: BMP2/4 plays an important role in bone formation in response to mandibular advancement by accelerating and enhancing the differentiation of mesenchymal cells into boneforming cells.