Interaction between xylitol and sorbitol in plaque metabolism.

Xylitol and sorbitol, when metabolized by microorganisms, are transported through the cell membrane and phosphorylated by membrane-bound phosphoenolpyruvate-dependent phosphotransferase systems. Sorbitol-6-phosphate may be oxidized by a sorbitol-6-phosphate dehydrogenase to fructose-6-phosphate and further decomposed in the Embden-Meyerhof pathway. Xylitol-5-phosphate - if not metabolized - may be toxic to the cell. There are few specific pathways known for xylitol metabolism in microorganisms. Due to structural resemblance between the xylitol and the sorbitol molecules interaction between xylitol and sorbitol metabolism is likely to occur. Xylitol - although only slowly taken up by plaque and oral microorganisms - may reduce plaque formation and cause an increase in plaque pH. Evidence for a phosphotransferase system for xylitol has recently been demonstrated in Strep. mutans, which may cause accumulation of xylitol-5-phosphate in the cell. Some studies carried out by the author and associates on acid production in the oral cavity from cell. Some studies carried out by the author and associates on acid production in the oral cavity from sorbitol in the presence of xylitol in chewing gum containing sorbitol reduces acid production from sorbitol. This may be explained by the following effects of xylitol: Reduction of plaque and the number of microorganisms on the teeth. This is thought to be a consequence of the toxic effect of xylitol-5-phosphate. Inhibition of acid production from sorbitol. This is believed to be a consequence of competitive blocking of the phosphotransferase system due to structural similarities between xylitol and sorbitol.