Effect of xylitol gum on salivary mutans streptococci concentration and plaque-pH: a randomized clinical trial in high caries risk schoolchildren

he effect of 11.6 g of xylitol daily (chewing gum) on salivary mutans streptococci (MS) and plaque acidogenity in a group of high caries risk Italian schoolchildren was studied. The hypothesis was that xylitol affects salivary MS and plaque pH. A randomized clinical trial was designed and performed with 204 subjects (acceptance rate 88%). Inclusion criteria were the presence of two or three caries lesions and salivary MS concentration >105 CFU/ml. Subjects were randomly assigned into xylitol and nonxylitol groups. The study design included one examination at baseline (t0), after 3 months of chewing (t1), after 6 months of chewing (t2) and after another 3 months of chewing (t3). The protocol consisted of two parallel arms: microbiological and plaque acidogenicity evaluations. Paraffin-stimulated whole saliva was collected in sterile vials and then processed for determination of MS concentration. Plaque acidogenicity was assessed using a microtouch electrode following a sugar challenge. Data were analysed for statistically significant differences using repeated one-way measures analysis of variance (ANOVA) and the area between the resting pH and the pH curve (integrated pH fall) was calculated. The differences between treatments were statistically significant in both arms of the study (p = 0.01 microbiological part and p = 0.035 pH part) and the interaction term for treatment and time was statistically significant (p <0.01). There was a marked decrease in CFU/ml for the xylitol group. The integrated pH fall was significantly greater (p <0.01) in the xylitol group than in the control group during the first 5 min after chewing. The results suggest that the use of xylitol gums has a beneficial effect on salivary levels of mutans streptococci and plaque acidogenicity.