Evaluation Of The Quality Of Mtwo NiTi Instruments System In Root Canal Retreatment And The Effects Of Root Canal Retreatment On Apical Microleakage

Objective:Evaluation of the quality of Mtwo NiTi instruments system in root canal retreatment and the effects of root canal retreatment on apical microleakage.Method:Thirty-four extracted premolars teeth (68 root canals) were collected, they were randomly divided into 3 experimental groups of 10 teeth each, in addition to a positive and negative control group of 2 teeth each.Group A:obturated with FR phenolaldehy deagent;Group B prepared with step-back technique and filled with gutta-percha cone and sealer; Group C:done nothing to the teeth until next step.After 30 days, every group were divided into 2 groups randomly:stainless steel hand files group and Mtwo NiTi instruments group. Stainless steel hand files group was filled with 0.02 tapered angle 40# master cones and AH-Plus obturated with cold lateral condensation. Mtwo NiTi instruments group was filled with 0.06 tapered angle 25# master cones and AH-Plus obturated with cold lateral condensation. After 30 days,the microleakge of the 4 groups was evaluated by dyeing.The operating time, broken files, negotiated canals and the microleakge length were recorded.Results:1. In Group A,B and C, the mean operating time of Mtwo NiTi instruments group was significantly shorter than stainless steel hand files group (P<0.05).2. In stainless steel hand files group and Mtwo NiTi instruments group, the mean operating time of Group C was significantly shorter than Group B, the mean operating time of Group B was significantly shorter than Group A (P<0.05).3. In Group A,B and C, the mean apical microleakage length of Mtwo NiTi instruments group was significantly shorter than stainless steel hand files group(P<0.05).4. In stainless steel hand files group and Mtwo NiTi instruments group,there was no significant difference between Group A and B (P>0.05). the mean apical microleakage length of Group C was significantly shorter than Group A (P＜0.05),the mean apical microleakage length of Group C was significantly shorter than Group B (P<0.05).Conclusion:1. The operating time of Mtwo NiTi instruments group was shorter than stainless steel hand files group.2. The apical microleakage length of Mtwo NiTi instruments group was shorter than stainless steel hand files group.3. If the root canal could be negotiated successfully, the kind of the first treatment do not affect the apical microleakage of it.