Evaluation of radicular dentin erosion and smear layer removal capacity of Self-Adjusting File using different concentrations of sodium hypochlorite as an initial irrigant

Objective. The aim of this study was to evaluate Self-Adjusting File (SAF) in the removal of smear layer and impact on the dentin surface using sodium hypochlorite (NaOCl) as an initial irrigation solution at 3 different concentrations combined with 1% EDTA. In addition, the erosive effect of this dual irrigation regime was examined. Study design. Root canal preparations were performed in 30 teeth using the SAF with a continuous irrigation device (Vatea) in a closed system in which the apical foramen was sealed. The vibration mode was on for 5 minutes during the preparation. Three different concentrations of NaOCl (1.3%, 2.6%, and 5.25%) and 1% EDTA were used for continuous irrigation. The final flush was also performed using NaOCl with the vibration mode on. The roots were split longitudinally and subjected to scanning electron microscopy (SEM). The presence of the smear layer was scored using a 5-point scoring system, and the erosive capacity of the irrigants were scored using a 3-point scoring system. Results. The results showed no significant difference in smear layer removal among different concentrations of NaOCl and among the regions. Clean dentin surfaces were observed in 80%, 70%, and 70% with a score of 1 or 2 of the apical thirds using 1.3%, 2.6%, and 5.25% NaOCl, respectively. The 1.3% and 2.6% NaOCl solutions showed similar erosion patterns on the root canal walls (P > .05); however, 5.25% NaOCl caused severe erosion (P < .05). Conclusions. When using the SAF with continuous irrigation and vibration, lower concentrations of NaOCl and EDTA can be recommended for efficient clinical removal of the smear layer even in the apical thirds and to avoid excessive erosion of root dentin. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;112:524-530)