Efficacy of various concentrations of citric acid at different pH values for smear layer removal

Objective. The efficacy of various concentrations of citric acid at different pH values for the removal of the superficial smear layer from dentinal surfaces was examined through the use of scanning electron microscopy. Study design. Fifty extracted teeth were irrigated with sodium hypochlorite (NaOCl) during instrumentation. Citric acid solutions at 50%, 25%, 10%, and 5% (wt/vol) concentrations were prepared. In addition, similar solutions of citric acid were buffered to pH 6. Citric acid solutions with original and buffered pH values were used as final rinses. Bidistilled water and NaOCl were used as controls. The data were analyzed by using nonparametric Kruskal-Wallis and Mann-Whitney U tests. Results. Lower concentrations with lower pH values removed smear layer more efficiently than the ones with higher pH values (P < .05), whereas no significant differences for higher concentrations were detected between low and high pH values. However, more destruction of peritubular dentin was observed at higher concentrations with low pH values. Conclusion. Within the limits of this study, lower concentrations of citric acid with its original pH were found to be as effective as higher concentrations in the removal of superficial smear layer.