Influence of Xylitol chewing gum on intraoral Mutans streptococci levels

High levels of Mutans streptococci (Ms) are associated with high caries risk.  Effective strategies to lower caries risk are aimed at lowering Ms levels.  Some studies seem to indicate that xylitol-sweetened chewing gum can markedly decrease the numbers of Ms and reduce the incidence of caries by up to 80% when chewed for at least five minutes per session for a total minimum daily dose of 6 grams.  Other studies have concluded that the caries reduction is a result of saliva stimulation from chewing sugar free gum. Objective: The purpose of this study was to measure Ms levels in human subjects before and after chewing xylitol-sweetened gum (X) or sorbitol-sweetened gum (S). Methods: After IRB review and informed consent, twenty first-year dental students (ages 22-36) were screened and separated into two similar groups based on sex, DMFS and baseline Dentocult^® SM Strep Mutans (Orion Diagnostica, Finland). Group 1 (G1) chewed two pieces of gum containing sorbitol (1g/piece) and Group 2 (G2) chewed two pieces of gum containing xylitol (1g/piece) for at least five minutes three times per day.  Subjects recorded the length of chewing time on a log to monitor compliance. Ms scores were checked after one week and again at four weeks and compared with a Wilcoxon rank-sum test.   Results:  The median Ms score for both patient groups at baseline was 2. After one week and 4 weeks, the S group remained at 2 (p>0.05) and the X group median score was 0 (p<0.05).   Conclusions: In this study chewing xylitol-sweetened gum lowered Ms scores after 1 and 4 weeks.  Chewing sorbitol-sweetened gum had no significant effect on lowering Mutans streptococci levels over the four week study.  Recommendations to lower patients' caries risk should include discussions about the use of xylitol-sweetened chewing gum.