A Morphometric Study of the Mandibular Foramen, Lingula, and the Incidence of Accessory Mandibular Foramina in Dry Mandibles.

introductionThe foramen situated on the ramus of the mandible on its medial surface is termed the mandibular foramen (MF), which opens up into a canal. The MF acts as a conduit to the inferior alveolar nerve and vessels. Determining the location of MF is very crucial to avoid injury to the inferior alveolar nerve during inferior alveolar nerve block or surgical intervention. The lingula is a tongue-shaped projection on the medial aspect of the mandible. It is important to study the variable shapes of the lingula for surgical procedures due to its relation to the neurovascular structure. The accessory MFs are foramina other than mandibular, mental, and lingual foramina. The present study aims to locate the MF, assess the shape of the lingula, and report the incidence of accessory MFs bilaterally.

methodsThe present study was performed in the Department of Anatomy, King George's Medical University, India, on adult human mandibles of North Indian origin and unknown sex. Exclusion of mandibles was done based on deformed bones, broken bones, or any surgical procedures such as partial mandibulectomy or mandibular reconstruction affecting bony reference points for measurement of various distances from MF. After the exclusion of such types of mandibles, a total of 30 mandibles (100%) were included in the present study. Distance of MF was taken in millimeters (mm) from various reference points of the mandible (closest point on anterior and posterior border of the ramus, most distant point on angle of mandible, lowermost point of mandibular notch, highest point of coronoid process (CP)). We noted the prevalence of the shape of the lingula and the incidence of accessory MFs in percentage. A paired t-test was used as a statistical test.

resultsThe mean distance of MF from the closest point of the anterior border of the ramus on the right and left sides was 17.14 ± 1.64 mm and 17.06 ± 2.18 mm, respectively (p = 0.805). The mean distance of MF from the closest point of the posterior border of the ramus on the right and left sides was 10.80 ± 1.77 mm and 10.83 ± 2.15 mm, respectively (p = 0.936). The mean distance of MF from the most distant point on the angle of the mandible on the right and left sides was 22.28 ± 3.50 mm and 22.06 ± 3.62 mm, respectively (p = 0.433). The MF was located 22.60 ± 4.20 mm and 22.53 ± 2.85 mm from the lowermost point of the mandibular notch on the right and left sides, respectively (p = 0.879). The MF was located 37.33 ± 3.62 mm and 37.42 ± 3.85 mm from the highest point of CP on the right and left sides, respectively (p = 0.803). Results revealed no significant difference in the location of MF from different bony features bilaterally. The most prevalent shape of the lingula on both sides of the mandible was truncated. Accessory MFs were present in 36.66% of mandibles.

conclusionsThe present study will help in assessing the precise location of MF, shapes of lingula, and incidence of accessory MFs, which will aid maxillofacial surgeons and oncologists in improving surgical outcomes by reducing failure of inferior alveolar nerve block. The findings for the laterality-wise location of MF were not statistically significant in the current study. For the exact localization of MF in the North Indian population, one additional criterion, i.e., distance from MF to the tip of CP, was taken in the present study.