This is an interesting review of the existing literature which attempts to address the practical issues associated with using PUI at the end of root-canal treatment procedure in the hope of obtaining a cleaner root-canal system. It will certainly alert practitioners to the existence of this approach, which may deliver better biologically prepared root canals, although the review does not present enough evidence to disqualify syringe irrigation.

It is well-documented that one of the most important procedures in nonsurgical root-canal treatment and retreatment is chemomechanical preparation of the root canal.1 Although intracanal procedures accomplish the mechanical portion, it is vital to adopt a complementary approach for biological preparation. The aim of this is to remove the pulp tissue and/ or micro-organisms there, and also remove any smear layer and dentine debris that occur following and/ or during treatment. Sodium hypochlorite (NaOCl) has been widely accepted as the gold-standard irrigation solution since its introduction in endodontics in 1936. As well as bleaching, deodorising and tissue-dissolving properties,2 NaOCl has been demonstrated to be an effective disinfectant.3

The technique of applying NaOCl to the root canal system does improve the overall effectiveness of biological preparation. Important considerations are, however, the gauge of the needle used, the concentration of the irrigation solution, and the total volume and methods used.4 In several studies mentioned in this review, it is not possible to divine all of these details. Also, the in-vitro experimental conditions differ from in-vivo studies in some aspects, among them, the volumes used for disinfection, the accessibility of microbes and the absence of other materials in in-vitro experiments which potentially protect bacteria in vivo.5 All of these considerations prevent any conclusion that PUI is more effective than syringe irrigation but it does appears that PUI could be an important adjunct in the management of primary endodontic diseases or root canal failures. There is a need for more experimental evidence and systematic reviews to shed light on this procedure.