Özet:

Objective: The aim of this study is to evaluate the working time of ProTaper and Mtwo retreatment systems for removal of three different resin-based filling materials during simulated retreatment.  Methods: 160 extracted maxillary anterior teeth were enlarged using two different rotary systems; ProTaper and Mtwo. The teeth were randomly divided into 8 groups of 20 specimens each. Six groups were filled with 3 different resin-based obturation materials, two groups were filled with an eugenol-based paste as control groups. In groups instrumented by ProTaper files, ProTaper Retreatment files, in groups instrumented by Mtwo files, Mtwo retreatment files were used for removal of root canal fillings. Time for reaching the working length (T1), time for re-preparation (T2) and total time for retreatment (Tt) were measured with a chronometer.  Results: Retreatment working time was evaluated for the systems used for preparation of the root canals. There was statistically significant differences between the ProTaper and Mtwo groups. T1, T2 and Tt were significantly higer in Mtwo groups when compared to ProTaper groups. There was statistically significant differences between the groups according to the obturation techniques. Teeth obturated with gutta-percha and AH Plus have shorter working time when compared to all the other obturation techniques.  Conclusions: T1,T2 and Tt of the teeth instrumentated with Mtwo were higher than the teeth instrumentated with ProTaper irrespective of the root filling material used. According to the results of our research, ProTaper Retreatment files were faster in removing root filling material from the root canal than Mtwo Retreatment files.

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