Fungal infection of the radicular dentin.

Although fungi have been detected in infected root canals, their precise role as endodontic pathogens has not yet been elucidated. The purpose of this study was to investigate the pattern of radicular dentin colonization by five fungal species. Bovine root sections were infected with each of the following fungal species: Candida albicans, Candida glabrata, Candida guilliermondii, Candida parapsilosis, and Saccharomyces cerevisiae. After 14 days, the sections were fixed in glutaraldehyde, split into two halves, critical point-dried in CO2, sputter-coated with gold, and examined under scanning electron microscopy. Regardless of the species, single or budding yeast cells were the only fungal forms observed. C. albicans colonized most of the specimens. On the other hand, the other four fungal species presented discrete or no colonization of the radicular dentin. C. albicans showed different patterns of dentin infection. In some specimens, colonization of the dentinal surface was slight and no penetration within dentinal tubules was observed. In the other specimens, some areas of the root canal walls were covered with large colonies of yeast cells and some dentinal tubules were heavily infected. The results suggested that whereas C. albicans showed the ability to colonize dentin, the other four fungal species did not. This can help to explain why C. albicans is the fungal species most often found in endodontic infections.