The Efficacy Of Different Retreatment Files On Removing Filling Material From Root Canals

Objective: To evaluate the efficacy of H files, Pro Taper Universal Retreatment and D-Ra Ce nickel titanium(Ni Ti) files on removing filling material from root canals.Methods: Forty-five extracted single-rooted mandibular premolars were selected for this study. All samples were prepared to F2 with Pro Taper Universal and obturated using laterally condensed gutta-percha and sealer. Samples were randomly divided into 3 groups(n=15), respectively with H files(group A),Pro Taper Universal Retreatment(group B) and D-Ra Ce(group C) Ni Ti files for removal of root canal filling material. Chloroform was used as a solvent in the retreatment procedures. Time to reach the working length(T1) and time required for the removal of gutta-percha(T2) were recorded; Eppendorf tubes were used to collect apical extrusion. The tubes were weighed before and after retreatment procedures. After completion of retreatment, bucco-lingual and mesio-distal radiographs were taken, the percentage of remaining filling material was measured using Auto-CAD software. Data were analysed by means of one way ANOVA and Mann-Whitney U test at a95% confidence level(P < 0.05).Results: The maximum residual filling material was detected in Group C(D-Ra Ce) while Group A(H files) showed the least(P < 0.05). Compared with H files, D-Ra Ce and Pro Taper Universal Retreatment can reduce the time required for retreatment(P < 0.05), but the difference between the latter two groups was not statistically significant(P > 0.05). The amount of apical extrusion generated by Pro Taper Universal Retreatment was the most(P <0.05).Conclusion: Under the present experimental conditions, none of the retreatment files could completely remove the filling material from root canals. Pro Taper Universal retreatment and D-Ra Ce could significantly reduce the operating time, but resulted in more apical extrusion.