Acidogenicity and acid tolerance of and isolated from plaque of healthy and incipient caries teeth.

BACKGROUND

Non-mutans low pH oral streptococci are postulated to contribute to caries etiology.

OBJECTIVE

This study was undertaken to investigate whether the acidogenicity and acid tolerance of clinical strains of and correlate with health or early-stage enamel caries.

DESIGN

and were isolated from plaque samples taken from the occlusal surfaces of second molars sampled at two different visits 4 years apart. All sites were sound at Visit 1; subjects were segregated into one of three groups based on the status of the site at Visit 2 and caries elsewhere in the dentition. Strains of and were evaluated for acidogenicity and acid tolerance, and the results correlated with the clinical status of the sites from which they were isolated. Mutans streptococci (MS) isolated from the plaque samples were also quantified, and the presence or absence of growth on pH 5.5 media or on media selective for bifidobacteria was recorded.

RESULTS

No significant positive correlations were found between the acidogenicity properties of the and clones and caries at either visit. Similar results were obtained for acid tolerance of clones but were inconclusive for clones. A statistically significant positive correlation between MS levels and caries (or future caries) was evident at both visits, but there were no statistical correlations with the growth on pH 5.5 media or media selective for bifidobacteria.

CONCLUSIONS

The low pH potential likely varies considerably among oral streptococcal species and is least likely to be found among strains of . Accordingly, the concept and constitution of 'low pH streptococci' may need to be re-evaluated.