Clinical aspects related to endodontic yeast infections

Abstract

Yeasts can be detected in 7–18% of infected root canals. They are commonly associated with persistent cases of apical periodontitis, but yeasts can also be isolated in primary apical periodontitis. Their relative proportion of the root canal flora is low, usually below 1%. Therefore, yeast detection with conventional microbiological methods may be difficult. Selective culture media such as Sabouraud dextrose agar combined with cultivation from undiluted sample should be used for primary isolation of yeasts in endodontic infections. Preliminary identification of yeasts is based on typical colony and cellular morphology and a positive catalase test. Detection by molecular biological methods is sensitive, but may occasionally also give false‐positive results. Candida albicans is the most commonly detected yeast species from infected root canals. It is typically found together with Gram‐positive bacteria such as streptococci, but can also be isolated in pure culture, which is an indication of its pathogenicity. A variety of virulence factors enable C. albicans to adhere to and penetrate into dentine. Furthermore, C. albicans tolerates harsh ecological conditions including high alkalinity. Calcium hydroxide is generally not efficient against oral yeasts in vitro; the in vivo effectiveness of calcium hydroxide is not known. However, sodium hypochlorite, iodine compounds, and chlorhexidine have proven effective against yeasts both in experimental conditions as well as in vivo and may offer effective treatment possibilities against endodontic yeast infections.