Endodontic filling materials DAG ØRSTAVIK The principal function of root filling materials is to prevent invasion of bacteria and infection of the root canal system after completed endodontic treatment. This is accomplished by the formation of a tight, permanent seal with the surrounding tooth structure, leaving no space for invasion of or colonization by bacteria. The materials can also have a direct antibacterial effect and kill the microbes when in contact with them. Materials applied onto larger areas of connective tissue, i.e. for retrograde root fillings or perforation repair, should also allow or stimulate complete repair or regeneration. Ideally, the selection of materials for various applications in endodontics should be based on clinical, scientifically valid data. However, most current endodontic practices and choice of materials are based on a convoluted history where data of varying relevance and validity is mixed with experts’ stated opinions and manufacturers’ advertising. In this review, the chemical, physical, and biological properties of different root filling materials are discussed together with their handling characteristics and recommended use in the clinic. Emphasis is placed on evidence generated from clinical practice and research. Received 21 September 2014; accepted 9 October 2014. Introduction Endodontic practice is largely defined by the consequences of dental pulp and root canal infections (1). The endodontic materials are placed in and on tooth substance as part of clinical efforts to eliminate and prevent these infections (2). Ideally, the antimicrobial part of treatment is completed and asepsis is established prior to the placement of endodontic filling materials. The prevention of new infection of the root canal system thus becomes their primary function (3). There are basically two ways of fulfilling this task: either prevent microbes from entering the tissues by physical means, or kill them when they try to penetrate the barrier created by the material. The former relates to the physical integrity and adaptation to tooth substance by the materials; the latter requires some form of biological activity, which in turn is dependent on the solubility of the material. Antimicrobial properties of the materials may also support our clinical attempts at disinfection of the root surface and canal system (4). In conventional root filling procedures, the area of contact with soft tissues is so small that material considerations other than filling and killing hardly come into play. However, in many other clinical situations the area of contact between the material and soft tissue is much larger, e.g. pulp exposures, perforations, and surgical approaches. Here the material must possess properties which permit (but ideally promote) healing and regeneration of the relevant tissues, in addition to preventing bacterial activity (5). There are thus three properties of overriding importance for the clinical performance of endodontic materials: sealing ability, antimicrobial activity, and biocompatibility. In addition, the materials must have handling properties which allow their proper placement, but handling properties are all subservient to the three primary functions (6). Several review papers have recently discussed various aspects of endodontic materials (7–10). The present review focuses on their primary functions as related to clinical performance. An attempt is made to apply the principles of evidence-based clinical practice in systematizing current knowledge (11). This knowledge has been acquired from an extremely wide array of different experiments and studies, ranging from theoretical computer models to randomized clinical experiments (12). It seems prudent to emphasize that Endodontic Topics 2014, 31, 53–67 All rights reserved © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd ENDODONTIC TOPICS 1601-1538 53