The anterior loop of the inferior alveolar nerve is a sensitive anatomical feature that should be taken into account during installation of dental implants anterior to the mental foramen. This study was conducted to explore the controversy regarding prevalence and length. A total of 452 mandible quadrants of 234 patients (age: 50.1 ± 13.3 years, 113 males, 121 females) were studied using cone-beam computerized tomography. After reconstructing axial, frontal, and sagittal slices, the region between the most anterior point on the mental foramen and the most anterior part of the mandibular nerve was inspected for signs of anterior loop presence. If positive, the length of the anterior loop was measured in mm as the distance between the anterior border of mental foramen and the anterior border of the loop. Prevalence and length of the anterior loop were compared statistically between sexes and age groups. The anterior loop was observed in 106 quadrants (23.5% of 451 quadrants) of 95 patients (40.6% of 234 patients), of whom 11 had bilateral anterior loops. Prevalences were similar in males (41%) and females (39%, chi-square P =.791). The mean anterior loop length was 2.77 ± 1.56 mm (95% CI: 2.5-3.1 mm), without significant sex (regression beta = -0.159, P = .134) or age (beta = -0.059, P = .578) differences. The anterior loop might exist in about 40% of patients, regardless of their gender. The mean safe anterior distance from the anterior loop is about 3 mm + (2.5-3.1 mm) = 5.5-6.1 mm, regardless of age.
Keywords: anterior loop of the inferior alveolar nerve; dental implantation; iatrogenic damage; maxillofacial anatomy; mental foramen.