下颌第二磨牙"C"形融合根及其根管形态的观察

目的　观察具有“C”形融合根的离体下颌第二磨牙牙根外形及根管形态。方法　通过牙根水平片切及透明标本的制作 ,观察 4 0颗下颌第二磨牙牙根的形态特点 ,并测量其长度。结果　牙根均在颊侧融合 ,牙根长度较正常牙长且有显著性差异 (P <0 .0 5 )。根管形态变异较多 ,仅 4 0 %呈现根颈到根尖的“C”形 ,3 0 %为“分号”形 ,10 %为“分离”形 ,2 0 %的牙根内各横断面形态可有不同。结论　下颌第二磨牙“C”形融合根的变异较多 ,不利于根管的彻底清理和充填

The Morphology of Roots and Canals in the C-Shaped Mandibular Second Molars

Objective To study the morphology of the fused roots and canals. Methods Through the canal transparent specimen and root transverse sections, the shape of canals and the length of roots were observed.Results All roots were fused buccally. The length of root was longer than normal, and the difference had significance . Many variations in root canal morphology, only 40 percent demonstrated a continuous C Shaped canal in the coronal, middle, and apical sections of the root. 30 percent exhibitied semicolon ,and 10 percent were separate canals. 20 percent canal shapes frequently changed at different levels.Conclusion These special morphologies of the C shaped mandibular second molars would be detrimental to canals debridement and obturation.