Back Ground: Several studies have shown the increase of the risk of mandibular angle fractures by the presence of the impacted lower third molar (IM3). Sport-related mandibular fracture is commonly observed in the younger patients, whose M3 are generally impacted and it easy to consider that the early information of the presence of this tooth is beneficial for preventing these traumatic lesion. Objectives: The purpose of this study was to clarify the influence of the eruption status of IM3 and decreased bony angle space on the incidence of mandibular angle fractures. Methods: 72 mandibular sides in 36 patients with mandibular fractures treated between April 1998 and March 2003 were analyzed. The eruption status of IM3 and the bony space of mandibular angle in the patients with IEM3 were analyzed by the panoramic radiographs. Results: Of 72 mandibular sides in 36 patients, 22 mandibular angle fractures were observed. The incidence of the angle fracture in the side with IM3 was 34.5% and that in the group without IM3 was 17.6%. The higher incidence of the angle fractures was observed in the groups with the mesioangular IM3 ranged 20 to 40 degrees. The group, in which the bony angle space was decreased more than 15 % by IM3, showed higher incidence of the angle fractures. Conclusion: The results of this investigation showed that IM3, in which the dental root directed toward the edge of the angle have a higher risk of the angle fracture in the sports-related mandibular fractures and the decreased bony space of the mandibular angle due to the presence of IM3 is considered to be a causative factor. To prevent the mandibular angle fractures during sports, the players and the coach should be aware of the presence of this tooth.

DESCENTE SPORTS SCIENCE Vol.25/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE