An anatomical and radiographic study of medial depression of the human mandibular ramus.

OBJECTIVES: To determine the prevalence of the medial depression of mandibular ramus (MDMR) in dry human mandibles and in clinical panoramic radiographs and to compare the prevalence in dentoskeletal deformities with Angle Class I occlusion. METHODS: Two hundred and fifty-one dry skulls and three groups of patients were used for this study: Group 1 consisted of 1358 panoramic radiographs from a general population, Group 2, 426 radiographs from individuals with Angle class I occlusion and Group 3283 individuals with dentoskeletal deformities. The prevalence of MDMR was determined in the skulls and each group and the shape from the radiographs alone. RESULTS: The prevalence of MDMR in dry mandibles was 33.9% (bilateral in 13.1% and unilateral in 20.8%). MDMR was found in 276 radiographs (20.3% - Group 1 - bilateral in 40% and unilateral in 59.5%). MDMR was more common in Group 3 compared with Group 2 (chi(2)=35.98 P<0.01). A triangular MDMR was the most frequent (39.7%). CONCLUSION: MDMR is a relatively common finding in panoramic radiographs. Patients with dentoskeletal deformities have a higher prevalence of MDMR and this should be taken into consideration if orthognathic surgery is proposed.