EFFECT OF SUGAR ALCOHOLS ON THE COMPOSITION AND METABOLISM OF A MIXEDCULTURE OF ORAL BACTERIA GROWN IN A CHEMOSTAT

Xylitol and sorbitol are effective as non-cariogenic sugar substitutes . A number of studies suggest that xylitol may have an additional, car ies-reducing effect. This study examines the effect of xylitol and sor bitol, when pulsed together with glucose, on the composition and metab olism of a mixed culture of oral bacteria grown in a chemostat. In thi s system, xylitol had the effect of reducing the rate and extent of ac id production when pulsed with glucose, compared with glucose pulsed a lone, enabling acid-sensitive species to persist in greater numbers. F urthermore, the enrichment of Streptococcus mutans, observed following glucose pulses in the absence of pH control, was prevented by xylitol . In contrast, sorbitol had the opposite effects and S. mutans increas ed in proportion. The study provides evidence for a mechanism by which xylitol could affect the ecology of dental plaque and thereby reduce the rate of dental caries.