Abstract
The effect of xylitol on growth, acid production and water-insoluble glucan formation of mutans streptococci under the additional condition of another monosaccharide was studied. The growth of mutans streptococci was measured by nephelometry using a spectrometer-20, and water-insoluble glucan was observed by inverted conf ocal laser scanning microscope (LSM) and transmission electron microscope (TEM) . The full growth of mutans streptococci required the further addition of glucose or fructose in trypticase soy broth, and the growth of mutans streptococci was inhibited or delayed by the addition of xylitol in trypticase soy broth. Upon the addition of 1% glucuse or 1% fructose in trypticase soy broth, the growth of mutans streptococci was not inhibited by the addition of 1-10% xylitol. However, the addition of 20% xylitol caused the carbohydrate chain of water-insoluble glucan, which was synthesized by mutans streptococci from sucrose, to shorten as shown by TEM observation, and changes in the quantity of nucleic acid were recognized by LSM observation.
The results suggested that the caries preventive effect of xylitol was remarkably inhibited by the existence of another monosaccharide which could be metabolized by mutans streptococci.
