Does the Position of the Mandibular Third Molar Have an Effect on the Lingual Bone Morphology? A Cone Beam Computed Tomography Evaluation.

Background/Objectives: This study aimed to investigate the association between the position of impacted mandibular third molars and the morphology of the lingual cortical bone using cone beam computed tomography (CBCT), and to determine how impaction depth and angulation influence the risk of lingual cortical perforation. Methods: CBCT scans of 120 impacted mandibular third molars from 71 adult patients were retrospectively evaluated. Teeth were classified based on Pell & Gregory's and Winter's classifications. Lingual cortical morphology was categorized as undercut, parallel, slanted, or round. The relationship between the root apex and the lingual plate was classified as non-contact, contact, or perforating. Linear measurements included cortical lingual bone thickness and the distance from the apex to the outer surface of the lingual cortex. Results: Lingual bone morphology showed significant associations with both impaction depth and angulation, with parallel morphology more common in deeper and more angulated impactions. Lingual cortical perforation was observed in approximately 30% of the teeth, predominantly at the apex, with horizontal and deeply impacted molars (Class II, Level C) representing the highest-risk configurations. Although cortical thickness and apex-to-cortex distance were significantly smaller in apically perforated cases, no definitive threshold could be established, and these parameters were insufficient as standalone predictors at the cementoenamel junction or mid-root levels. Conclusions: Tooth angulation and impaction depth are significant predictors of lingual bone morphology and perforation risk. CBCT imaging is therefore recommended beyond low-risk cases (Level A, Class I, vertical) to improve preoperative planning, strengthen informed consent, and guide surgical strategies aimed at minimizing complications and enhancing patient safety.