Evaluation of Mandibular Lingual and Foramen Location in Class I, Class II, and Class III Patients and its Significance in Sagittal Split Ramus Osteotomy

The precise location of the mandibular lingual (ML) and foramen (MF) is clinically significant because they are crucial anatomic markers for the inferior alveolar nerve protection in sagittal split ramus osteotomy. To determine the position of the ML and MF among subjects with class I, class II, and class III skeletal patterns to obtain information that could be useful for interventions in mandibular ramus. A retrospective study of 324 mandibular ramus from 162 patients was performed to evaluate the distance from the MF to the occlusal plane (OP) and the distance of the ML to the MF, OP, and the margin of the mandible ramus. The MF was more often located below the OP in class III (55.1%), compared with class I (29.0%) and class II (45.3%) patients ( P <0.05). The distance from the ML to the MF in skeletal Class III patients (10.15 ± 1.56 mm) was found to be greater than class I (9.25 ± 1.52 mm) and class II (8.34 ± 1.79 mm) patients ( P <0.001). And the distance from the ML to the OP was shown to be longer in class III (9.40 ± 2.53 mm) than in class I (6.85 ± 2.55 mm) and class II (6.99 ± 2.53 mm) patients ( P <0.001). Therefore, we believe that a low medial horizontal cut at the height of OP is dangerous for Class III patients. And the safe zone for the high medial horizontal cut over the ML should be determined according to the patient’s skeletal patterns.