Objective The aim of this study is to investigate the influence of cone beam computed tomography (CBCT) and micro-ultrasound technique for the treatment of three mesial canals in mandibular first molars. The three mesial canals according to Pomeranz's classification were characterized. Methods A total of 75 permanent mandibular first molars for root canal treatment were randomly selected from patients belonging to the age group of 14-60 years. After preparing the access cavity and locating the main canals, the middle mesial canal orifices in all teeth were determined with an endodontic explorer under direct vision (StageⅠ), under magnification with the aid of micro-ultrasound (Stage Ⅱ), and with the combined use of CBCT and micro-ultrasound to remove the dentin wall and calcifications (Stage Ⅲ). Results Middle mesial canals were detected in 4.0%, 18.7%, and 22.7% of the teeth in StagesⅠ-Ⅲ, respectively. Statistical analysis showed significant differences (P<0.05) between StagesⅠand Ⅱ with regard to middle mesial canal detection. The number of Stage Ⅲ was more than that of Stage Ⅱ. The difference between the two stages was no significant. Among the 17 middle mesial canals, "confluent", "fin" and "independent" anatomies were 52.9%, 35.3%, and 11.8%. Conclusion When used with adjunctive aids, including CBCT, micro-ultrasound facilitates dental clinicians in the location and treatment of middle mesial canals.
目的 评估锥形束CT （CBCT）结合显微超声技术定位疏通下颌第一磨牙近中三根管的能力，并依照Pomeranz的分类标准描述其分型特征。方法 从年龄在14~60岁的患者中选择75颗需要根管治疗的下颌第一磨牙。髓腔预备和主根管定位后，所有牙齿均在直视下用牙髓探针探查近中中央根管（MMC）（第一阶段），然后在显微超声技术的帮助下探查寻找（第二阶段），最后CBCT结合使用显微超声技术选择性去除牙本质领和钙化物后探查MMC（第三阶段）。结果 MMC的疏通率在各阶段分别为4.0%、18.7%、22.7%；第二阶段较第一阶段显著增加，差异显著（P<0.05）；第三阶段较第二阶段有所增加，但差异无统计学意义。根据Pomeranz的分类，“融合”解剖型，“歧状”解剖型，“独立”解剖型所占比例分别为52.9%、35.3%、11.8%。结论 CBCT结合显微超声技术的应用会增加临床医生探查疏通MMC的能力。.
Keywords: cone beam computed tomography; mandibular first molar; three mesial canals; ultrasound.