| Objective To investigate the difference of mandibular bone mineral density in class I malocclusion patients with different vertical facial types, and to provide clinical reference for orthodontic treatment of patients with different facial types. Methods Eighty-eight patients with class I malocclusion were selected.Among those, 32 patients with average-angle ( 12 males and 20 females, with an average age of 21 years old) were divided in normal control group, and 27 patients with high-angle (10 males and 17 females, with an average age of 22.5 years old) and 29 patients with low-angle (15 males and 14 females, with an average age of 21 years old) were divided to two experimental groups.All the 88 patients took the digital panoramic radiography photos.Bone mineral density of the mandible was analyzed using panoramic mandible index ( PMI) .Results In control group, sPMI was 0.280 ±0.035, and iPMI was 0.348 ±0.052.In the group with highangle, sPMI was 0.248 ±0.033, and iPMI was 0.313 ±0.044.In the group with low-angle, sPMI was 0.285 ±0.038, and iPMI was 0.361 ±0.061.PMI index was statistically different among the three groups (P<0.05).Conclusion The mandible bone mineral density in high-angle group is lower than that in normal group.The mandible bone mineral density in low-angle group is higher than that in normal group.PMI reflects the change of bone mass in the cortial bone.It reflects bone mineral density of the mandible bone indirectly.It provides a convenient and intuitional method to measure bone mineral density of the mandible.Meanwhile, the result of bone mineral density in the mandible can indicate bone mineral density of the whole body, which may prevent osteoporosis earlier. |