Evaluation of Intracanal Smear Layer Removal after Passive Microvolume Irrigation with Sodium Hypochlorite and Rotary NickelTitanium Instruments: An In-vitro Study

Introduction: Passive Microvolume Irrigation (PMI) with Sodium Hypochlorite (NaOCl) has been proposed as a new method for root canal disinfection. It is based on the concept that irregular surface characteristics of endodontic instruments can carry NaOCl into the canal space with controlled fluid volume, without applying any pressure. Aim: To compare and evaluate the efficacy of 3% and 5% NaOCl PMI, Saline PMI, and 3% NaOCl Standard Irrigation (SI) in removing the Smear Layer (SL) from the root canal walls at the cervical, middle, and apical thirds of single-rooted teeth. Materials and Methods: This study was conducted in the Department of Conservative Dentistry and Endodontics at Vishnu Dental College, Andhra Pradesh, India. The study was conducted in February 2018. Forty maxillary central incisors with a single canal, extracted within three months of the study, were collected. The teeth were divided into four groups (n=10) based on the irrigation method: Group-1 (3.0% NaOCl SI), Group-2 (3.0% NaOCl PMI), Group-3 (5.0% NaOCl PMI), and Group-4 (Saline PMI). All samples were instrumented upto F4 size with Protaper rotary files, and a final rinse of 17% Ethylenediaminetetraacetic Acid (EDTA) was used. SL removal was evaluated using Scanning Electron Microscope (SEM). The data were analysed using Statistical Package for Social Sciences (SPSS) 21.0. Statistical tests used were Kruskal Wallis and Mann-Whitney-U tests. A p-value of 0.05) in SL removal between 3.0% NaOCl SI, 3.0% NaOCl PMI, and 5.0% NaOCl PMI in the middle and apical thirds of the root canals. However, 5.0% NaOCl PMI showed significantly higher efficiency in SL removal at the cervical third compared to the other groups (p