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

Abstract

Root sections were inoculated with one of two strains of Actinomyces viscosus or a strain of Streptococcus sobrinus and then incubated for 9 days in Trypticase soy broth (TSB) containing 0.25% glucose or TSB supplemented with 0.25% sucrose (TSB+S). Lesion progression was measured from microradiographs. One section from each group was examined with a transmission electron microscope. Lesion progression was associated with a fall in the pH of the medium. However, lesion progression was not correlated with the mean 48-hour pH of the medium. In both TSB and TSB + S, lesion progression with A. viscosus was significantly greater than in the S. sobrinus group. However, the mean 48-hour pH value in TSB + S was lower than that in the S. sobrinus group. Plaque formation in TSB was, subjectively, least in the S. sobrinus group. Examination of transmission electron micrographs revealed bacteria penetrating the surfaces of the sections and extending into the lesion in the A. viscosus groups but not in the S. sobrinus group. This in vitro bacterial plaque model of root caries may be suitable for investigations of the bacterial etiology of root-surface caries and the virulence factors associated with pathogenicity.

In vitro growth, acidogenicity and cariogenicity of predominant human root caries flora

“…This implies that all bacteria were used either singly or in combination possessed the ability to produce adequate quantities of short chain carboxylic acids to induce demineralization during the 24-h incubation period. Our results are comparable to those of Firestone et al 20 who used two strains of A. viscosus and one strain of S. sobrinus in TSB-S to produce root lesions using similar methodology. They reported pH minima as low as 4.36 and 4.20, in cultures of A. viscosus M100 and S. sobrinus 6715, respectively, that led to cementum demineralization.…”

“…20,21 Columbia blood agar (Difco) plates were used to monitor the contamination in the liquid incubation media after every culture.…”

Molecular Analysis of Bacterial Species Associated with Childhood Caries

“…A. gerencseriae has been isolated from root caries (4) but has not been associated with caries in children. It is interesting that a closely related species, Actinomyces naeslundii serotype II (A. viscosus), has been associated with invasion into the tooth structure and early lesion formation (9). Actinomyces species have also been associated with early root caries lesions, although S. mutans has been found more commonly in advanced lesions (33).…”

Genotypic diversity of oral Actinomyces naeslundii genospecies 1 and 2 in caries‐active preschool children

“…Previous studies have associated the presence of A. naeslundii with root caries (7), particularly its initiation (16, 33). However, its role in the cariogenicity of children's teeth has not been studied (3, 25, 36).…”