CBCT assessment of lingual cortical plate morphology and pre-existing perforation in impacted mandibular third molars

Background Impacted mandibular third molars may be associated with surgical complications related to the lingual cortical plate. However, detailed information on coronal and apical lingual cortical thickness and the factors influencing pre-existing lingual cortex perforation remains limited. Methods This retrospective cross-sectional study evaluated cone-beam computed tomography (CBCT) scans of 201 patients with impacted mandibular third molars. Lingual cortical thickness was measured at coronal and apical levels, and pre-existing perforation was recorded. Age, sex, side, angulation (Winter classification), impaction depth (Pell and Gregory classification), and root morphology were analyzed. Non-parametric tests were used for group comparisons, and binary logistic regression was performed to identify independent predictors of perforation. Results Mean lingual cortical thickness was 2.04 ± 1.12 mm at the coronal level and 0.86 ± 0.80 mm at the apical level, with an overall mean of 1.45 ± 0.70 mm. Pre-existing perforation was detected in 1.5% of cases. Apical (p = 0.02) and overall thickness (p = 0.01) were significantly lower in the perforation group. Angulation type significantly affected coronal (p = 0.046) and overall thickness (p = 0.028), and impaction depth was associated with coronal thickness (p = 0.041). Sex, side, and root morphology showed no significant associations. Age was the only independent predictor of lingual cortex perforation (OR = 1.306; 95% CI: 1.088–1.568; p = 0.004). Conclusions The lingual cortical plate adjacent to impacted mandibular third molars is frequently thin, particularly at the apical level, whereas pre-existing perforation is rare. Thinner cortex and increasing age significantly increase the risk of lingual cortical perforation. Detailed preoperative CBCT evaluation is essential for safer surgical planning.