下颌第二磨牙C形根及根管系统的显微解剖研究

A microanatomy study of C-shaped root and root canal system in mandibular second molars

目的:通过髓腔显微解剖学方法探讨C形根及根管系统的显微解剖结构形态及其形成原因。方法:C形根第二下颌磨牙40颗,中国墨汁灌注髓腔以廓清髓腔结构,分别于根管的颈、中、尖1/3处制备140~160μm厚的横磨片共120例,数字显微镜观察并分析标本中牙本质牙骨质界、牙本质小管、融合剩余、牙本质生长线的显微解剖形态规律,以及C形根管各型的分布规律。结果:所有磨片中,C形根各根均作为一个整体被同一牙本质牙骨质界包绕(100%);牙本质小管走行方向的改变形成根管及融合剩余,融合剩余在根管颈、中、尖各段的总检出率为69.2%,且分布于所有40颗C形根磨牙中(100%)。所有磨片中,牙本质生长线同心围绕整个C形根管系统(100%),各根管并未发现独立的牙本质生长线围绕。C形根管各型的发生率在各个水平上发生率不同,其中根管颈1/3处以C1型和C2型为主;根管中1/3处以C2型和C3型为主;根管尖1/3处以C3型为主,差异有统计学意义(P<0.01)。结论:C形根为单根,因Hertwig上皮根鞘末端突起未能融合而形成;C形根根管系统结构复杂,牙本质增龄性改变导致C形根根管系统的复杂性。

Objective:To investigate the microanatomical structure and the causes of C-shaped roots and root canal system by microanatomy.Methods:A total of forty second mandibular molars with C-shaped root,were filled with Chinese ink to clear the pulp cavity.120 cases of transverse grinding plates with thickness of 140-160μm were prepared at 1/3 of the neck,middle and apex of the root canal.The microanatomical morphology of dentine cementum,dentine tubules,fusion residue,dentine growth line and the distribution of c-shaped root canals were observed and analyzed under digital microscope.Results:The C-shaped root was surrounded by the dentino-cemental junction as the single root(100%).The root canal and fusion residuals was formed by the dentinal tubules,that run from the dentino-cemental junctions.The incidence of the fusion residual was 69.2%,and distributed in all of forty C-shaped root second mandibular molars(100%).The whole C-shaped root canal system was surrounded by the incremental line concentrically(100%).The prevalence of C-shaped root was different between different levels.C1 and C2 was dominant at the coronal-third point;meanwhile,C2and C3 was dominant at the middle of the root canal;however,C3 was dominant in apical-third point,and the difference was statistically significant(P<0.01).Conclusion:C-shaped roots are single roots,resulting from failure of fusion of protrusions at the end of Hertwig epithelial root sheath.The structure of c-shaped root canal system is complex,and the aging of dentin results in the complexity of C-shaped root canal system.