Effect of Master Apical File Size and Taper on Irrigation and Cleaning of the Apical Third of Curved Canals

Objective: Canal preparation generates a substantial amount of debris and smear layer (SL). The size and taper of the Master Apical File (MAF) affects on penetra- tion of irrigants and subsequently canal cleaning efficacy. The aim of this study was to evaluate the effect of MAF size and taper on penetra- tion of irrigants to the apical third of curved mesiobuccal (MB) canals of mandib- ular first molars. Materials and Methods: Eighty-nine human mandibular first molars were divid- ed into one control group (n=5) without rotary instrumentation and 6 experimental groups (n=14 each) that were prepared with the following RaCe rotary files as MAF: 25.04 (group1), 25.06 (group 2), 30.04 (group 3), 30.06 (group 4), 35.04 (group 5) and 35.06 (group 6). All the experimental groups were rinsed with 2 ml of 17 % EDTA followed by 2 ml of 5.25% NaOCl. Debridement of the MB canals was evaluated using scanning electron microscope (SEM). The data were statisti- cally analyzed using Kruskal-Wallis and Mann-Whitney U tests (P<0.05). Results: Group 6 (MAF=35.06) showed 100% acceptable debridement. This rate was 92.9% for MAF=35.04. In group 4 (MAF=30.06) smear layer (SL) was re- moved in the three-forth of the samples and debris was removed in 92.9% of them. Acceptable debridement was not achieved in most samples of groups 1 and 2 (25.04 and 25.06, respectively) and the mentioned two groups had statistically significant difference in this respect with the other groups (P<0.05). Conclusion: Based on this study, 30.06 may be considered as the minimum MAF size for acceptable debridement.