Studies directly relating radiological findings to the risk of postoperative wound infection (PWI) in impacted mandibular third molars (M3) are limited and poorly understood. This study aimed to clarify the radiological risk of PWI.

Twenty-six patients who developed PWI after M3 extraction were retrospectively analyzed using orthopantomography (OPG) and computed tomography (CT) before M3 extraction to determine the association between M3 impaction status and PWI. These were compared with an equal number of non-infected groups. Moreover, the possibility of assessing the same risk in OPG as in CT imaging was examined.

Multivariate analysis identified class III and position B of the Pell and Gregory classification system as independent risk factors for PWI. On CT, an axial overlap distance (AOD) >3.5 mm was significantly associated with PWI. Furthermore, the sagittal overlap distance (SOD) and AOD of the OPG were significantly greater in group III-B. A strong positive correlation was observed between SOD and AOD.

These results indicate that class III, position B, and an AOD >3.5 mm may be novel risk factors for M3 PWI. The strong correlation between SOD and AOD suggests that the risk assessment for PWI can be performed by evaluating OPG alone.