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

OBJECTIVES: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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. CLINICAL RELEVANCE: 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.