We investigated oxidative potential water (OPW) for its ability to remove the smear layer using a scanning electron microscope. OPW has been studied mainly in Japan and is known to suppress bacteria and viruses without harming living systems. We found that OPW used as in irrigant during and after root canal instrumentation is as effective as 5% NaOCl or 17% EDTA for opening and keeping patent the dentinal tubules.