Chelators were first introduced into endodontics by Nygaard-Ostby in 1957, who recommended the use of a 15% EDTA solution. A few years later, a detergent was added in order to increase the cleaning and bactericidal potential of the EDTA solution. Since then, the search for ideal chelating agents has continued and led to many new chelator preparations in endodontics. This paper reviews the relevant literature on chelating agents, presents an overview of their chemical and pharmacological properties and makes recommendations for their clinical use. Schlagwörter: chelators, dentine hardness, EDTA (ethylenediamine tetra-acetic acid), smear layer