Fig. 2From: Variations of root and canal morphology of mandibular second molars in Chinese individuals: a cone-beam computed tomography studyCoronal plan of Vertucci’s type I configuration. a a oval canal: the coronal plan of root canal is small and narrow and the cross-section is oval or round; b a flat canal: the coronal plan of root canal is large and wide and the cross-section is flat; c a expand canal: the middle part of the canal is expandedBack to article page