The first part of this study reviewed the characteristics of calcium hydroxide (Ca(OH)₂) and summarized the results of in vitro studies related to its antimicrobial effects. The second part of this review covers in vivo studies including human clinical studies and animal studies. The use of Ca(OH)₂ as an intracanal medicament represented better histological results in animal studies. However, human clinical studies showed limited antimicrobial effects that microorganisms were reduced but not eliminated through the treatment, and that some species had resistance to Ca(OH)₂. Most of clinical outcome studies supported that there is no improvement in healing of periapical lesions when Ca(OH)₂ was applied between appointments. Further studies are required for the antimicrobial effects of Ca(OH)₂, and search for the ideal material and technique to completely clean infected root canals should be continued.

The goal of endodontic treatment is the prevention and control of pulpal and periradicular infections. Calcium hydroxide (Ca(OH)₂) has been widely used in endodontics as an intracanal medicament to eliminate the remaining microorganisms after chemomechanical preparation. The purpose of this article is to review the antimicrobial properties of Ca(OH)₂ as an intracanal medicament in root canal treatment. The first part of this review details the characteristics of Ca(OH)₂ and summarizes the results of in vitro studies related to its antimicrobial effect. The antimicrobial effect of Ca(OH)₂ results from the release of hydroxyl ions when it comes into contact with aqueous fluids. Ca(OH)₂ has a wide range of antimicrobial effects against common endodontic pathogens, but is less effective against Enterococcus faecalis and Candida albicans. The addition of vehicles or other agents might contribute to the antimicrobial effect of Ca(OH)₂.