Three-dimensional analysis of the inferior alveolar nerve in relation to mandibular morphology

This study aimed to evaluate the relationship between mandibular morphology and the localization of the inferior alveolar nerve (IAN) using cone-beam computed tomography (CBCT).

A retrospective study was conducted using CBCT scans. Mandibular morphology was classified according to the 14-type. These types are as follows: Straight, Pen Shape, Oblique, D Type, B Type, Kidney, Hourglass, Sickle, Golf Club, Toucan Beak, Tear, Cudgel, Basal, and Saddle. The vertical position of the IAN was assessed by dividing the mandibular cross-section into four equal zones from superior to inferior (Zone 1-4). The horizontal position was evaluated by dividing the cross-section into three regions: buccal, middle, and lingual. Measurements were conducted bilaterally at the first, second, and third molar regions. Parameters such as age, sex, presence of teeth, mandibular type, and IAN position were recorded and analyzed.

Significant associations were observed between mandibular morphology and both vertical and horizontal positions of the IAN in all regions (p < .001). For vertical localization, the nerve was most frequently found in Zone 2 and Zone 3. Age was also a significant predictor: increasing age was associated with deeper nerve positioning (e.g., right first molar, Zone 3: Estimate = -0.038, p < .001). Regarding horizontal positioning, the IAN was predominantly located in the lingual zone. The Straight type showed the highest rate of lingual localization in several regions (e.g., left third molar: χ² = 398.985; p < .001). Presence of teeth was associated with more superficial (Zone 1-3) and buccal/middle nerve positioning, whereas edentulous regions tended to show deeper and more lingual localization.

Mandibular morphology, age, and the presence or absence of teeth significantly influence the position of the inferior alveolar nerve. Specific morphological types such as Straight and Cudgel can predict nerve course, which is crucial for surgical planning. Deeper nerve localization with increasing age and superficial positions in dentate regions are important clinical considerations. Individualized anatomical assessment using CBCT is recommended to enhance patient safety and minimize the risk of nerve injury in oral and maxillofacial interventions.