Mutans streptococci caries and chlorhexidine

Mutans streptococci, particularly Streptococcus mutans and Streptococcus sobrinus, can be shown to be highly associated with caries in humans. Together with Lactobacillus spp., they are regarded as significant odontopathogens. Because of their association with dental disease, an evaluation of the numbers of Mutans streptococci organisms in plaque and saliva may aid in the diagnosis of caries activity. In conjunction with this concept, control and prevention of caries has been sought by reducing the numbers of bacteria colonizing an individual. Despite the associations between dental disease and Mutans streptococci, which can be demonstrated in groups of people, these methods have not been entirely successful. Because of the wide range of factors involved, counts are not very effective in diagnosing caries activity or risk in an individual. Nevertheless, counts may be used to establish a normal pattern of colonization for a patient, and deviation from this pattern will indicate a change in their oral status, which can be included as a parameter in diagnosis. Accurate and relatively simple commercial tests for counting mutans streptococci and lactobacilli are available. In patients with high caries activity and high counts of mutans streptococci, chlorhexidine may be employed as an adjunct to other preventive measures. Chlorhexidine delivered in a gel form has been shown to be effective in the control and prevention of caries. Combinations of chlorhexidine with fluoride may be even more effective. Sustained release devices, like varnishes, reduce the numbers of mutans streptococci in a patient's mouth to levels below detection for long periods, but their effectiveness in preventing and controlling caries has not yet been assessed. The decision to use microbiological methods to aid diagnosis, and chlorhexidine to reduce or eliminate mutans streptococci, rests with the practitioner. Although the microbiological tests for caries activity or prediction are not 100 per cent accurate, they can be useful in certain situations. In addition, chlorhexidine as an adjunct in control and prevention of caries has been shown to have value. This short review introduces readers to the literature, so that they will not dismiss microbiology, but make decisions on the use of microbiological methods based on their own experience and the experience of others.