不完全的清創及修形，牙齒的微滲漏，或是複雜的根管結構可能會導致初次的根管治療失敗，在這些情況下，第一優先考慮的治療方式應該是非手術性的根管再治療，不同的化學及機械方法已被用來移除根管空間內的封填材料，雖然要從根管分枝及牙本質小管移除全部的封填材料以確保乾淨的根管壁是很因難及非常秏時的，非手術的根管再治療還是有很高的成功率。

Incomplete cleaning and shaping, microleakage, or complex anatomy may result in failure of initial endodontic treatment. In these situations, non-surgical endodontic retreatment should be considered as the first choice. Different chemomechanical methods have been used to remove the root-filling materials from the endodontic space. Although removal of all root canal filling materials from anatomic ramifications and dentinal tubules to ensure cleaner root canal walls is difficult and time-consuming, non-surgical endodontic retreatment still have high success rate.