Influence of impacted mandibular third molars on pathological changes on themselves and adjacent tissues across different age groups: a cross-sectional study.

OBJECTIVE

To investigate the effects of different types of impacted mandibular third molar (IMTM) on lesions in situ and on adjacent tissues at different ages.

METHODOLOGY: Cone Beam Computed Tomography (CBCT) images of 1007 IMTM cases were retrospectively analyzed. Associations between age, gender, impaction type, distal alveolar bone condition of mandibular second molar (MSM), IMTM-MSM contact status and occurrence of lesions on IMTM and its adjacent tissues were evaluated using Pearson's chi-squared test and Fisher's exact test.

RESULTS

MSM distal alveolar bone defects showed the highest incidence among all IMTM-related lesions (79.2%), followed by MSM distal external root resorption (ERR) (25.5%) and MSM distal caries (10.4%). Mesioangular (96.2%, p<0.001) and horizontal (95.9%, p<0.001) IMTM were associated with more severe bone defects and the incidence increased with age. IMTM-MSM surface-to-surface contact was significantly associated with MSM distal caries severity (12.5%, p<0.001) and distal ERR (29.5%, p<0.001). Inflammatory resorption of MSM distal alveolar bone was significantly correlated with MSM distal caries (47.1%, p<0.001), ERR (36.5%, p<0.05), distal alveolar bone defects (100%, p<0.001), and IMTM caries (14.1%, p<0.05). Study design followed the STROBE guidelines.

CONCLUSION

Mesioangular impaction, horizontal impaction, MSM-IMTM surface-to-surface contact, and MSM distal alveolar bone in a state of inflammatory resorption greatly affect lesions on IMTM and its surrounding tissues. These findings suggest the prophylactic extraction in young adults (18-25 years) with high-risk impactions, while recommending observation or cautious management for asymptomatic older patients without signs of inflammatory bone resorption.