Xylitol and Sorbitol Effects on the Microbiome of Saliva and Plaque

Subjects: Study protocols were approved by the Ethics Committees of the UWI, St. Augustine. Thirty healthy volunteers from The University of the West Indies (UWI), St. Augustine, Trinidad were enrolled in the study. To be eligible, subjects must have had at least 20 teeth, provided written informed consent and been willing to comply with study procedures. Subjects with systemic, infectious or inflammatory diseases or taking medicines, antibiotics or fluoride in the last month, habitual consumers of xylitol / sorbitol-containing products and mouth rinses, with abnormal salivary flow (<1ml / min), pregnant, on contraceptive pills, or with abnormal dietary habits were excluded. Consent obtained at the initial visit was verified at the second visit, prior to sample collection. The subjects were examined in the dental chair after thorough medical and dental histories were recorded. The clinical examination involved examination of the soft tissues and then dental hard tissue charting for presence of decayed, missing or filled teeth. No radiographs were used. The presence of untreated dental caries or periodontitis were not used as exclusion criteria. The decayed, missing, and filled teeth for each individual at the initial visit was documented for calculation of the index of decayed-missing-filled permanent teeth (DMFT) score.

Chewing gums: Xylitol gum (Epic Spearmint; 1.5g/pellet) designated Gum X contains 70% xylitol in addition to gum base, natural flavors, soy lecithin, gum arabic, titanium dioxide, carnuba wax. Gum S (Eclipse Spearmint), was similar except that xylitol was replaced by 63% sorbitol and 2% maltitol and aspartame was included. Gums were packed in colour-coded containers. Codes were kept confidential from the participants and researchers who interacted with them until study completion.

Study design: This prospective cross-over, double-blind, randomised study lasted 14 weeks (March - June, 2015). Throughout, subjects were instructed not to use mouthwashes or xylitol products, to consume a normal diet, continue their usual tooth brushing and to report use of antimicrobial medications. Subjects reporting the latter were dropped.

Subjects were randomly allocated to two groups, A and B (see Figure 1). Both groups entered a 4-week "washout period" during which no gum was chewed, followed by a 3-week treatment period (treatment period 1) during which Group A used Gum X and Group B used Gum S (2 gum pieces, 3 times daily after meals for 6 minutes). Both groups then underwent another 4-week washout period before entering treatment period 2 during which Group A used Gum S and Group B used Gum X for 3 weeks.

Sample collection: Saliva and plaque were collected from participants immediately before and after each treatment period (Figure 1). Subjects were instructed not to brush their teeth or use any other oral hygiene procedures at least 24 hours before sample collection, and not to eat or drink at least 1 hour before. For saliva collection, subjects chewed sterile paraffin wax and whole saliva produced was collected for 5 minutes in sterile tubes. The subject was asked to drool into the labelled 50ml collection tube (Falcon sterile, conical polypropylene tube with flat-top screw cap). This process was repeated multiple times in order to collect larger volumes of saliva (2-5 ml). The saliva was transferred via sterile pipettes into labelled sterile centrifuge tubes which were stored at -70˚C until use.