CBCT-based evaluation of mandibular third molar impaction and its effects on adjacent second molars in a Saudi population: a retrospective study of 420 scans

This study evaluated the association between impacted mandibular third molars (MTMs) and second molar pathology in a Saudi cohort using cone-beam computed tomography (CBCT), analyzing specific risk factors and comparing findings descriptively with international data. In a retrospective analysis of 420 consecutive CBCT scans from a single‑center, from a referral-based CBCT archive, not a population-based sample, MTM angulation, depth, and cemento-enamel junction (CEJ) distance were assessed. Pathology was evaluated using CBCT-adapted caries (ICCMS) and bone loss criteria. Multivariate logistic regression identified predictors, from which an internal CBCT-based risk score was derived and assessed via ROC analysis. Mesioangular impaction was most prevalent (59.5%). A CEJ distance < 6 mm was the strongest predictor, increasing severe caries odds by 3.22-fold and bone loss odds by 3.98-fold. The internally assessed risk score showed excellent discrimination for bone loss (AUC = 0.81). Compared internationally, the cohort had higher mesioangular impaction (59.5% vs. 41.2%) and bone loss prevalence (53.2% vs. 38.1%), with similar caries rates. Key risk factors were mesioangular orientation, deep impaction, and close CEJ proximity, with periodontal bone loss being the predominant pathology. Findings confirm anatomical predictors and reveal population-specific patterns. CBCT facilitates detailed risk stratification. The internally derived risk score may aid in identifying cases at higher risk for periodontal compromise, informing individualized monitoring and treatment planning.