Caries on Root Surfaces Exposed Following Gingivectomy in Conventional Rats Infected With Streptococcus Sobrinus and Actinomyces Viscosus

Abstract

To study the ability of bacteria associated with coronal caries to initiate root surface caries, a rat model was used. Root surfaces were exposed by gingivectomy in rats fed a caries-promoting diet and orally inoculated with either Actinomyces viscosus M-100, Streptococcus sobrinus (mutans) 6715, or both. A fourth group received a diet containing antibiotics. The animals were sacrificed 64 days following the gingivectomy performed on the right molar quadrants. Gingivectomy significantly increased exposed lingual root length and root caries incidence. There were no caries on non-gingivectomy root surfaces. Root surface caries incidence in the groups inoculated with A. viscosus and A. viscosus plus S. sobrinus did not differ. For both these groups, root caries incidence was significantly greater than that for the group inoculated with S. sobrinus alone. Root caries incidence in this latter group did not differ from that in the control group (J Periodontol 1989;60:624-627).

In vitro Demineralization by Strains of Actinomyces viscosus and Streptococcus sobrinus of Sound and Demineralized Root Surfaces

“…In support of this hypothesis, A. viscosus M100 but not S. sobrinus 6715 was reported to initiate root caries in a rat model of root caries (Firestone et al, 1989). It has been suggested that in root caries, in addition to species-dependent factors, there may be differences in strain-dependent virulence factors which may be a more sensitive indicator of pathogenicity (cariogenicity) than the species to which the strain belongs (Komiyama et al, 1986(Komiyama et al, , 1988Bowden, 1990; van Houte et al, 1990).…”