Use of a novel body mandibular plane (mental foramen-protuberance menti) in analyzing mandibular asymmetry compared with conventional border mandibular plane.

Objectives: To compare a novel body mandibular horizontal plane (mental foramen-protuberance menti; Body-MHP) with the conventional border mandibular horizontal plane (gonion-menton [Me]; Border-MHP) to assess mandibular body inclination and dental compensation of skeletal Class III patients with and without facial asymmetry.

Materials and methods: Retrospective data obtained from diagnostic cone-beam computed tomography of 90 skeletal Class III patients (mean age, 21.67 ± 2.93 years; range, 15.0-30.6 years) were divided into symmetry (n = 30) and asymmetry groups (n = 60). The asymmetry group was subdivided into roll (n = 30) and non-roll types (n = 30). The differences in body inclination and dental measurements (distance and angle) according to two mandibular planes (Body-MHP and Border-MHP) were assessed in the groups and subgroups.

Results: Mandibular body inclinations relative to the Body-MHP were not different in the roll-type asymmetric mandible between the sides, while those relative to the Border-MHP were different (P < .001). For the mandibular first molar positions relative to the Border-MHP, the differences in vertical distance between the sides were undermeasured and the inclination differences were overmeasured when compared relative to the Body-MHP.

Conclusions: The Body-MHP demonstrated better bilateral similarity in body inclination compared with the Border-MHP in patients with roll-type facial asymmetry. The novel body mandibular plane ensures an accurate diagnosis for tooth movement and jaw surgery, particularly in the roll-type asymmetric mandible.