Abstract: Objective: To analyze the correlation between the eruption status of the mandibular third molar and the distal caries in the mandibular second molar. Methods: 204 patients who had eruption problems with their third molars were involved in this study. CBCT images were used to analyze the distal caries in the mandibular second molar, location of the third molars(Pell and Gregory classification), the impacted angulation of the third molar, and the distance of the cement-enamel junction(CEJ) between the second molar and third molar. Results: The prevalence of distal caries in the mandibular second molar was 78.4% when the third molar existed, and there was no difference between male and female patients (P=0.165). No significant difference was demonstrated among the Pell and Gregory classification groups (P=0.646). The distal caries in the mandibular second molar were most prevalent where the impacted third molar situated at a mesial angle of 40~80° (P<0.001). When the distance of the CEJ between the second molar and third molar was 6~9 mm, the distal caries in the mandibular second molar was apt to occur (P<0.001). Conclusion: The distal caries in the mandibular second molar was closely related to the impacted angulation (40~80°), and the distance of the CEJ between the second molar and the third molar (6~9 mm), which kind of impacted third molar should be extracted as early as possible.

Key words: mandibular third molar, mandibular second molar, distal caries, cone beam CT

摘要： 目的：研究下颌第三磨牙萌出状态与第二磨牙远中邻面龋坏的相关性。方法：临床收集因下颌第三磨牙不适而就诊的患者204例，运用锥形束CT分析下颌第二磨牙远中邻面龋坏与第三磨牙阻生类型(高位、中位、低位)、阻生角度以及两磨牙的釉牙骨质界距离（cementoenamel junction, CEJ）等因素是否存在相关性。结果：在下颌第三磨牙存在的情况下，第二磨牙远中邻面龋坏发生率高达78.4%；性别差异无统计学意义（P=0.165）；高位、中位和低位阻生的龋坏发生率差异无统计学意义（P=0.646）；而当第三磨近中阻生角度为40~80°时，第二磨牙远中邻面最易发生龋坏，与其他阻生角度组的差异有统计学意义（P<0.001）；当第二磨牙与第三磨CEJ距离在6~9 mm时，第二磨牙远中邻面龋坏高于其他组，差异有统计学意义（P<0.001）。结论：下颌第三磨牙近中阻生角度、第三磨牙与第二磨牙的CEJ距离与第二磨牙远中邻面龋坏的发生密切相关。当第三磨近中阻生角度在40~80°间，且两磨牙间的CEJ距离在6~9 mm时，第二磨牙远中邻面更容易发生龋坏，此类阻生齿建议尽早拔除。

关键词: 下颌第三磨牙, 下颌第二磨牙, 远中邻面龋, 锥形束CT

CLC Number: 

• R782.13