# Concentration in Saliva and Antibacterial Effect of Xylitol Chewing Gum: In Vivo and In Vitro Study
## 1 Introduction  
Dietary fermentable carbohydrates are among the main triggers for the development of cariogenic biofilm [1]. Several preventive strategies are recommended to control the risk of caries; dietary changes, with reduce intake of sweetener and the use of sugar substitutes, are probably among the most suggested [2].  
Several benefits of polyols, particularly xylitol, have been suggested for general and oral health, such as increasing tight junction and barrier formation of the skin, modulating intestinal microbial composition, reducing nose, throat, and ear bacterial infections, influencing bone health, stimulating immunity, and increasing metabolic health [3].  
Consumption of polyol, particularly xylitol, through chewing gum or tablets, is reported to reduce dental plaque, the concentration of cariogenic bacteria, such as _mutans streptococci_, leading to areduced caries increment [4; 5]. Although the xylitol mechanism is not fully known, several studies demonstrate the benefits on caries both in children and adults, showing that the polyol possesses both noncariogenic and cariostatic properties. The supposed effective daily dose of xylitol is between three and eight grams and frequent and prolonged intakes are recommended to obtain long-lasting benefits [2]. The anti-caries effect of xylitol is associated with suppression of _mutans streptococci_ and modification of their virulence [5; 6].  
When xylitol is administered, the frequency of administration, the dose-response, and the minimal salivary concentration are important parameters that have to be assessed. However, only afew studies have evaluated the concentration of polyol in saliva after the intake of products containing xylitol, with discordant results [7; 8; 9]. Since there are no clear indications of salivary concentrations after the intake of different products, this can lead to using these products in a way that is not optimal for achieving the complete release of xylitol (e.g., mastication time of chewing gum might be not sufficient to ensure the complete release of the polyol); it is of high relevance to obtain reliable data on salivary xylitol concentrations.  
While a fairly large number of studies have been conducted on the effect of xylitol administration on caries-associated bacteria [9; 10; 11; 12], few studies include the effects of this polyol on other oral strains, such as those associated to periodontal disease [13; 14]. In these studies, although xylitol consumption has been shown to reduce the streptococci counts, it has not affected the bacterial composition of the dental plaque. Therefore, the acquisition of information on the antibacterial activity of xylitol on different bacteria strains (i.e., periodontal bacteria and other oral saprophytes) is of extreme interest.  
This work aimed at assessing the salivary concentration of xylitol released from two chewing gums containing different amounts of the polyol in a sample of healthy volunteers. In addition, the in vitro antibacterial effect of xylitol chewing gum was tested against different strains of oral microorganisms related to caries and periodontal disease.