Efficacy of various root canal irrigants on removal of smear layer in the primary root canals after hand instrumentation: A scanning electron microscopy study

Aim: The purpose of this in-vitro study is to determine the efficacy of various irrigants in removing the smear layer in primary teeth root canals after hand instrumentation. Materials and Methods: The present study consisted of 30 human primary incisors which were sectioned at the cementoenamel junction horizontally. The specimens were divided randomly into four experimental and one control group having six teeth each and each group was treated with the specific irrigant. 5.25% NaOCl, 5.25% NaOCl + 10% EDTA, 6% citric acid, 2% chlorhexidine, saline (control) were the irrigants evaluated for efficacy in removal of smear layer. The specimens were split along the longitudinal axis using a chisel after placing superficial grooves in cementum not extending to the root canal. The exposed surface was subjected to scanning electron microscopic analysis to reveal the efficacy of irrigants in removal of smear layer. The representative areas were evaluated twice at 15 days interval by a single evaluator. The scale for the smear layer removal by Rome et al was modified and used in the present study. Results: The pictures from the scanning electron microscopy showed that among the tested irrigants, citric acid has the best efficacy to remove the smear layer without altering the normal dentinal structures, which was supported by the lowest mean smear scores. The pictures from the 10%EDTA + 5.25% sodium hypochlorite group showed that even though it removed the smear layer, it adversely affected the dentine structure. SEM pictures of the other groups like sodium hypochlorite, chlorhexidine revealed that these irrigants does not have the capacity to remove the smear layer in primary teeth. Conclusions: The results of the present study clearly indicate the superior efficacy of 6% citric acid than the other tested irrigants on removing the smear layer in primary teeth root canals.