Comparision Of Removing Efficiency Of Four Ni-Ti Root Canal Retreatment Instruments In Anterior Teeth Root Canals

Comparision of removing efficiency of four Ni-Ti root canal retreatment instruments in anterior teeth root canalsRoot canal therapy is main method of pulpitis and apical periodontitis at present. If primary treatment is failure,root canal retreatment is necessary. It can remove infected material which the primary treatment left. There are two kinds of instruments for removal of root canal remainder:one which is applied by hand directly takes too much time and uses great effort; the other one by engine avoids those disadvantages.Any instrument can not remove obturator in root canal thoroughly. The remainders affect prospective curative effect of root canal retreantment.So removing efficiency of instrument is one of indexes which signify prospective curative effect of root canal retreantment. At present removing efficiency of kinds of instruments is focal, but results are incompatible,because empirical methods are localized, destructive and subjective. Micro computed tomography is non-destructive three-dimensional technique. It can calculate volume of obturator removed in root canal precisely. It is objective. In this experiment, we also check if different root canal filling methods affect the removing efficiency of instrumentWe need sixty anterior teeth, clean out, measure the working length "16mm " and carve the root canals to0.06taper and30size.Then we assign the teeth meanly and randomly into three groups. Every group is applied different filling methods:cold lateral condensation technique, hot vertical condensation technique and supersonic lateral condensation technique. Third, every group is divided into four groups according to different retreatment instruments: Protaper group, M-Two group, D-Race group and R-Endo group.Record how long to remove the obturator thoroughly, if the instrument is destroyed or not and if the obturator is pulled out of root apical foramen or not According to statistics, the experiment results show that there are significant differences between cold lateral condensation technique with D-Race retreatment instrument and other groups. It has high-performance which remove most obturator in every seconds. There are obturators pulled out of root apical foramen in all groups,but D-Race group has least cases Instruments are not destroyed under operation. A little part of obturator are left on root canal wall,distributing around1/3root tip.Conclusion:1.The group, cold lateral condensation technique with D-Race retreatment instrument has high-performance which remove most obturator in every seconds.2. There are obturators pulled out of root apical foramen in all groups,but D-Race group has least cases.3. A little part of obturator are left on root canal wall,distributing around1/3root tip.