Actinomyces of infected dental root canals.

The aim of the present study was to identity Actinomyces occurring in infected dental root canals. Out of twenty-five isolated Actinomyces strains, four were A. israelii, four were A. naeslundii, four were A. odontolyticus, and six were A. viscosus. Seven strains could be identified only as Actinomyces spp. The relative frequency of various species of Actinomyces isolated from root canals was similar to that of carious dentin. The Actinomyces strains were usually part of polymicrobial infections. These infections could usually be eliminated by one or two conventional endodontic treatments. In two cases, however, A. israelii was repeatedly isolated in pure culture from the root canals. These two infections had to be eliminated by means of periapical surgery.