Abstract: Objective To compare tooth glue cleaning effect and root tip chipping removing amount in root canal retreatment among methods of G bore+manual K file， Protaper Universal retreatment and Reciproc. Methods 60 invitro single root solenoglyphic teeth were selected and root canal preparation was made， glass ionomer was filled and sealed for the teeth lasting for 30 days. Then they were divided into three groups at random， 20 in each group. Grub root canal filler was cleaned respectively with G bore+stainless manual K filing（group A）， Protaper Universal retreatment(group B) and Reciproc single filing(group C). The condition of filler removal was evaluated by root tip Xray film and scanning electron microscope. The cleaning effect of 3 groups root canal filler was compared， filler elimination operating time was recorded and the total amount of tooth glue chipping of apical foramen in each group was calculated by weighing method. Results Filler residues existed in all root canal walls of the 3 sample groups. Root canal wall filler residues in Group B and Group C were obviously less than those in Group A (P<0.05)， and eliminating effect of Group C was superior to that of group B (P<0.05). Compared to Group A， both Group B and Group A could reduce retreatment time (P<0.05). Group A removed the largest amount of root tip chipping， Group B took the second place and that of Group C was the least. Conclusion Nickeltitanium instrument is superior to manual instrument not only in cleaning effect， operating time but also in apical foramens chipping amount. Reciproc single killing as well is superior to Protaper retreatment killing.

Key words: root canal retreatment, manual instrument, Protaper Universal retreatment, Reciproc single filing