Xylitol, a naturally occurring sugar alcohol currently approved for use in foods, pharmaceuticals and oral health products in more than 35 countries has been shown to reduce cariogenic bacteria and tooth decay [1–5]; particularly delivered by either gum or lozenge . Our previous studies [2, 7] have reported on the minimally effective dose and frequency of use of xylitol delivered via pellet chewing gum to reduce Streptococcus mutans, a tooth decay pathogen. It is thought that xylitol's significant anti-caries effect is a result of constant S.mutans suppression  and alteration in virulence  from frequent and chronic exposure to xylitol-containing products. Although xylitol chewing gum is effective, new innovative ways to deliver xylitol at clinically effective levels are needed because chewing gum is neither safe, for the very young, nor acceptable, in schools, in the U.S. . Nevertheless, repeated long-term clinical studies of the various xylitol vehicles are not feasible. Thus, the development of a surrogate test of a xylitol delivery system is warranted.
There have been two studies examining salivary xylitol levels after the intake of various xylitol-containing products in children [10, 11], and none in adults. Lif Holgerson et al  determined salivary xylitol concentrations in children (mean age 11.5 years) after using a variety of xylitol-containing products (chewing gums, lozenges, candies, rinse, and fluoride toothpaste). All products were consumed in a single session with a brief rinse of distilled water immediately following consumption and a 10 min washout between xylitol products. It appears that saliva was collected from the floor of the mouth with a pipette. This resulted in recovering a large amount of the xylitol in the product but the method lacks any fidelity to actual conditions under which the oral flora is exposed to xylitol. Furthermore, it was unclear if saliva was collected the same way after consumption of the xylitol product. The researchers found that the xylitol products elevated salivary xylitol concentrations between eight to 16 minutes after xylitol product use. Tapiainen et al , in a second study, found salivary xylitol concentrations in preschool-aged children were immediately elevated after chewing gum or when a xylitol syrup was squirted into the mouth with a syringe but were undetectable after 15 minutes. Saliva was collected in a different manner depending on the age of the child; under age 3 saliva was collected directly from the mouth via a pipette while children age 4 and older spat through a funnel into test tubes. It is unclear how and when saliva was collected during xylitol administration in these children as the protocol is not detailed. For both studies, salivary xylitol concentrations were determined by enzymatic assay using a polyol dehydrogenase-based procedure (Boehringer Mannheim, Germany). The assay has a detection limit of approximately 200 ng/mL.
This paper describes a valid and reliable method to compare salivary xylitol concentrations during use of xylitol-containing products using a standardized and powerful method of chemical analysis, high performance liquid chromatography (HPLC). HPLC is a method of separating, identifying, and quantifying compounds in a sample. It has been used previously to measure xylitol and other sugar alcohols in gum and confectionary products [12, 13]. For the HPLC assay, the lower limit of detection of xylitol, using the standard curve, is 0.2 ng/mL. Validity is the extent to which a test accurately measures the desired phenomenon it is attempting to measure . Reliability is the extent to which the test is in agreement, where agreement may occur across two time periods (e.g., test-retest), between comparable forms of the same test, between individual sections of a test, or among different raters [15–17]. Two studies which address the presence and time course of xylitol in saliva delivered via a variety of xylitol-containing products are described. This paper specifically examines the presence and time course (peak and duration of detectable amounts) of xylitol concentrations in saliva for xylitol chewing gum (pellet and stick forms), xylitol gummy bear, and xylitol syrup; and compares the total xylitol-saliva time course curve (area under the curve) of xylitol pellet chewing gum to a commercially available xylitol stick gum, xylitol gummy bear and xylitol syrup.