Minimal Apical Enlargement for Penetration of Irrigants to the Apical Third of Root Canal System: A Scanning Electron Microscope Study

BACKGROUND The aim of this study was to determine minimal apical enlargement for irrigant penetration into apical third of root canal system using scanning electron microscope (SEM). MATERIALS AND METHODS Distobuccal canals of 40 freshly extracted human maxillary first molar teeth were instrumented using crown-down technique. The teeth were divided into four test groups according to size of their master apical file (MAF) (#20, #25, #30, #35 0.06% taper), and two control groups. After final irrigation, removal of debris and smear layer from the apical third of root canals was determined under a SEM. Data was analyzed using Kruskal-Wallis and Mann-Whitney tests. RESULTS Smear layer removal in apical third for MAF size #30 was comparable with that of the control group (size #40). CONCLUSION Minimal apical enlargement for penetration of irrigants to the apical third of root canal system is #30 size.