A simple method to locate mandibular foramen with cone-beam computed tomography and its relevance to oral and maxillofacial surgery: a radio-anatomical study.

PURPOSE: The mandibular foramen (MF) cannot be palpated clinically and its location is variable at the medial surface of mandibular ramus. Nevertheless, determining its exact location is very important to the oral and maxillofacial surgeon for the relevant anesthetic and surgical ramus procedures. The aim of this study was to analyze the position of MF using cone-beam computed tomography (CBCT) to help the surgeon in identifying reliable 'target area' for the inferior alveolar nerve (IAN) block and 'safety zone' for mandibular ramus osteotomies approached extra-orally.

MATERIALS AND METHODS: This radio-anatomical study examined all CBCT radiographs for patients treated over 2 years. Distances from MF to the anterior (A) and posterior (P) borders of the ramus, mandibular incisura (MI), mandibular notch (MN), and mandibular occlusal plane (O) were measured by a reliable examiner, followed by calculation of ratios to determine the horizontal and vertical position of MF. Patients' details were then recorded. Student's t test and One-Way-ANOVA test were used to analyze data.

RESULTS: A total of 210 CBCT radiographs were included and belonged to 210 subjects; 91 males (43.3%) and 119 (56.7%) females, with mean age (± SD) of 43.70 ± 19.08 years. The horizontal and vertical positions of MF differed significantly (P < 0.001) according to age, but generally calculated at least 40% of AP and MIMN distances from P and MI, respectively.

CONCLUSION: This study suggested the '40% rule' to locate the 'target area' for IAN block and 'safety zone' for ramus osteotomies approached extra-orally.