Anterior loop of the mental nerve: a cone-beam computed tomography analysis of its prevalence and surgical implications in implant dentistry.

BACKGROUND: Anterior loops of the mental nerve are important anatomical variations in which the inferior alveolar canal extends anteriorly beyond the mental foramen before looping back. These structures pose a risk of neurosensory injury during procedures such as dental implant placement and bone grafting in the interforaminal region. Cone-beam computed tomography (CBCT) provides high-resolution, three-dimensional images that are crucial for accurately identifying and mapping anterior loops, thereby helping prevent surgical complications. This CBCT study was designed to investigate the prevalence, radiographic characteristics, morphometric dimensions, and demographic correlations of anterior loops of the mental nerve in a subpopulation from the Najran Region. MATERIALS AND METHODS: In this retrospective CBCT study, 1000 hemimandibles from 500 patients were systematically evaluated using CBCT scans. Two calibrated examiners assessed the scans to categorize the mandibular canal configuration, measure the length of identified anterior loops, and document associated parameters, including mental foramen position, shape, and exit direction, as well as the presence of accessory mental foramina. Statistical analyses, including chi-squared and nonparametric tests, were used to determine associations with demographic variables such as gender (male and female), age groups (20-40, 41-60, and > 60), and side (right or left). A p value of less than 0.05 was considered statistically significant. RESULTS: Anterior loops had a prevalence of 6.5%, with a statistically significant association between gender and mandibular canal patterns (p = 0.0016). Higher prevalence rates were noted in males (9.1%) than in females (4.2%). Anterior loopshad a mean length of 2.10 ± 0.42 mm and ranged from 1.49 to 3.72 mm. No significant differences in length were detected by gender, age, or side, with p values of 0.618, 0.264, and 0.849, respectively. The most common position of the mental foramen was type II, located between the apices of the first and second premolars (61.0%), and the predominant mental foramen shape was round (66.5%). Additionally, a highly significant side-specific prevalence of accessory mental foramina was observed (p < 0.001). CONCLUSIONS: The occurrence of anterior loops was significantly associated with gender and mandibular side, and accessory mental foramina were more prevalent on the left side than on the right. Preoperative CBCT assessment of anterior loops is essential to prevent mental nerve injury during interforaminal surgery. The identified prevalence, gender- and side-specific variations, and measured loop lengths support a recommended safety margin of at least 2 mm anterior to the mental foramen in implant planning.