Assessment of the relationship between the three-dimensional precise location of the mandibular third molar and the volume ratio of the impacted mandibular third molar to the mandibular angle, and the patterns of mandibular angle fracture: A retrospective study

This study aimed to evaluate the relationship between the precise three-dimensional location of the third molar (M3) and mandibular angle fracture (MAF) patterns and to assess the effect of the volume ratio occupied by M3 in the mandibular angle on fracture patterns. The location of M3 was assessed in 218 patients with MAF using computed tomography reconstruction. The bone volume of the mandibular angle and the bone volume occupied by M3 were measured to calculate the volume ratio of M3 to the mandibular angle (M3/MA). MAF patterns were categorized into simple fracture (Type I), displaced fracture (Type II), and comminuted fracture (Type III) based on fracture severity. The results showed that the location of M3 significantly influenced MAF patterns (vertical position: P = .001; horizontal position: P = .002; angulation: P = .027, respectively) and the volume ratio of M3/MA was significantly higher for Type III fracture than Types I and II (P < .001). Regression analysis showed that the horizontal position and angulation of M3 and the volume ratio of M3/MA were the main predictors for comminuted MAF. A larger volume ratio (odds ratio [OR], 1.201; 95% confidence interval [CI], 1.037–1.391; P < .014), Class III position (OR, 7.978; 95% CI, 1.275–49.910; P < .026), and horizontal angulation (OR, 7.212; 95% CI, 1.028–50.581; P < .047) of the M3 were more prone to comminuted MAF than simple fracture. Our findings indicate that the location of M3 significantly affects MAF patterns, and that M3 may weaken the mandibular angle by occupying more bone space, thereby increasing the risk of a comminuted fracture.