Results:The frequencies of lateral canals were 39.4% and 36.7% in the mesiobuccal root (MBR) of maxillary molar s and in the mesial root(MR)of mandibular molar s separate roots,respectively.

• 4%25,下颌磨牙近中根侧支根管平均出现率36。7%25,磨牙的近中颊根及近中根均出现较多的侧支根管及管间侧支。(2)约2/3的根尖孔位置不在根尖。