Patterns of Impacted Third Molars and Their Association With External Root Resorption and Distal Caries in Adjacent Second Molars: A CBCT Study

Background:This study assessed patterns of third molar impaction and their associations with external root resorption (ERR) and distal caries in adjacent second molars according to age, sex, impaction type, and position using conebeam computed tomography (CBCT) scans. Material/Methods:Of 1180 CBCT scans assessed, 220 met the inclusion criteria.Sagittal CBCT images were used to assess patterns of third molar impaction (vertical, horizontal, mesioangular, and distoangular), impaction depth, ERR extent, and distal caries status (caries-free, enamel caries, dentin caries, or caries extending to pulp) in adjacent second molars.Multivariable logistic regression explored significant predictors of ERR and distal caries. Results:Mesioangular impaction was the most frequent pattern (45.5%), and Class C was the most common impaction depth (54.5%).ERR was present in 71.8% of cases, and Class 2 was most prevalent (31.8%); distal caries affected 40.9% of adjacent second molars.Impaction pattern was significantly associated with both ERR and distal caries (P < 0.001).In multivariable analysis, mesioangular impaction was the strongest independent predictor of ERR (P < 0.001).Age older than 30 years was independently associated with higher odds of both ERR (P = 0.049) and distal caries (P < 0.001); distoangular impaction and greater impaction depths (Classes B and C) were associated with significantly lower odds of distal caries (P = 0.012 and P < 0.001, respectively). Conclusions:Mesioangular impaction was associated with higher odds of ERR in adjacent second molars; the association for horizontal impaction was not robust in sensitivity analysis.ERR and distal caries prevalences were higher among older participants in this sample.