Assessment of impacted mandibular third molars and inferior alveolar canal contact: correlation with classification systems on cone-beam computed tomography

Abstract

This study analyzed the distribution patterns of impacted mandibular third molars (IMTMs) using the Winter and Pell & Gregory classification systems, which guide surgical planning and complication risk assessment. Additionally, the spatial relationship between IMTMs and the inferior alveolar canal (IAC) was evaluated with cone-beam computed tomography (CBCT) to enhance preoperative risk stratification. A total of 1594 IMTMs were retrospectively reviewed in patients with available panoramic and CBCT imaging. Angulation was classified according to Winter, while depth and ramus relation were categorized using Pell & Gregory. CBCT was used to assess IAC relationships. Associations between classifications and IAC contact were analyzed, and logistic regression identified independent risk factors. Mesioangular impaction was most frequent (37.6%), and Class II Level B was the predominant Pell & Gregory type (29.6%). CBCT showed IAC contact in 83.5% of cases, most commonly superior and buccal. Logistic regression revealed horizontal impactions had significantly lower odds of contact (OR=0.57, p=0.005), while deep types such as Class III Level C strongly predicted contact (OR=10.22, p<0.001). A “between roots” IAC configuration, undetectable on panoramic radiographs, was noted in 7.5%. While Winter classification offers moderate predictive value, Pell & Gregory-particularly deeper and more posterior subtypes-correlates strongly with IAC involvement. Findings highlight the value of CBCT in high-risk IMTM cases to improve radiographic assessment of the canal–root relationship and surgical planning.