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Objective To investigate the effect of the eruption status of mandibular third molars (MTM) on alveolar bone defects of mandibular second molars (MSM) using cone beam computed tomography (CBCT). Methods A total of 79 patients with impacted MTM combined with alveolar bone defect of MSM treated in our hospital from June 2018 to July 2019 were enrolled in this study. Occlusal plane angle (AOP), types of MTM impaction, and cementoenamel junction (CEJ) distances between distal MSMs and mesial MTMs (TMCEJ-DCEJ) were determined by CBCT. The general information of the patients, including gender and age, was also reviewed to analyze the influencing factors on alveolar bone defect of MSM. Results As for the patients aged ≥65 years, there were no significant differences in bone resorption between the distal and mesial alveolar bone. However, the bone resorption of the distal alveolar bone was greater than that of the mesial alveolar bone in the patients at age of 25~34, 35~44, 45~54 and 55~64 years (P < 0.05). Significant differences were observed in the bone resorption among different age groups (P < 0.05). For the 79 patients with impacted MTM combined with alveolar bone defect of MSM, 43 cases had mild, 20 moderate and 16 severe defects. The severity of alveolar bone defect in MSM was significantly correlated with age, ratio of CEJ-defect distance to tooth root length, AOP, type of MTM impaction and the TMCEJ-DCEJ of the patients (P < 0.05). Conclusion The eruption status of MTM can affect the alveolar bone defect of MSM. With the aid of CBCT, AOP of 11°~79°, high impacted MTM, and TMCEJ-DCEJ distance of 6~9 mm can increase the incidence of caries on the distal aspect in MSM and dental caries in MTM. |
