Association between Basal Bone Height in Mandibular posterior region and Facial Type

To evaluate the basal bone height (BBH) in the posterior region of mandible among subjects with different vertical facial dimensions, using panoramic radiographs. For this cross-sectional retrospective study the pretreatment panoramic and lateral cephalograms of 100 subjects (52 female and 48 male) were selected. Based on their vertical (MPA & Facial index) and horizontal (ANB angle) skeletal patterns, they were further classified into nine subgroups (combination of three vertical and three horizontal skeletal patterns). The BBH below the 400 mandibular molar teeth (first and second permanent molars on either side) were measured. The distance D1, measured between the apex of mandibular molars to the lower border of the mandible and the distance D2, measured between the lower borders of the mandibular canal to the lower border of the mandible. Differences in BBH in posterior region of mandible between patients with vertical (hyper- and hypo-divergent) and horizontal (Class I, II and III) skeletal patterns were analyzed using the Student?s t-test. Measurements were further evaluated for right and left sides, sex and age. The distance D1 and D2 were greater in hypo-divergent and were shorter in hyper-divergent , and the differences were statistically significant (p < 0.05). However, combination of both vertical and horizontal skeletal pattern showed that distance D1 was greater in Class I with hypo- divergent and Class II with normal divergent (p<0.05) and was shorter in Class I with hyper- divergent (p<0.005). Also, D2 was greater in class II with hypo-divergent and was shorter in class I with hypo-divergent (p<0.005). There is a significant difference between the BBH in the molar region of mandible among subjects with different facial types. Howeverwhen considering horizontal skeletal pattern, the results showed that a higher MBB height is associated with Class II malocclusion.