The abilities of different toothpastes to prevent and repair early tooth decay.

This randomized controlled study will use a double-blind, five-way crossover design to assess the effects of rinsing with five dentifrice formulations on the promotion of enamel and dentine remineralization and/or preventing enamel and dentine demineralization, using an established intra-oral caries model. Ten human volunteers will be selected from staff and students of the Melbourne Dental School, University of Melbourne to participate. Potential participants will be given a Plain Language Statement detailing what they will be asked to do and a consent form to sign and date if they agree to participate. Each participant will wear a custom-made removable palatal acrylic appliance with four slabs of human enamel and two slabs of human dentine attached. The enamel and dentine slabs will be pre-sterilized and contain subsurface lesions created in the laboratory. Participants will wear the appliances for 24 hours a day over five 14 consecutive-day treatment periods (including weekends). At the end of each treatment period participants will rest from the study for one week before commencing the next treatment period. During the rest period, the research team will replace the slabs on the appliances with new pre-sterilized slabs. During each treatment period participants will rinse with a sucrose solution and then a slurry of one of five dentrifices four times a day while they are wearing their appliances. Five different dentifrice formulations containing widely-used, commercially-available ingredients will be tested. Two dentifrices will act as controls; one positive control will be a commercially available fluoride dentifrice and the other negative control will be identical to the first control except it will not contain fluoride (the active ingredient). The active ingredient in the positive control will be 1100 parts per million fluoride as sodium fluoride (0.243% sodium fluoride). There will also be three experimental dentifrice formulations with only one of these (experimental formulation 1) containing an active ingredient (sodium monofluorophosphate). Ingredients in the other two experimental formulations are widely-used excipients and not actives. Experimental formulation 1 will contain 1500 parts per million fluoride as sodium monofluorophosphate (1.14% (w/v) sodium monofluorophosphate) as the active agent. The other two experimental dentifrice formulations will not contain fluoride and will act as placebos for the experimental dentifrice formulation containing sodium monofluorophosphate. These two experimental dentrifice formulations (Experimental formulation 2 and Experimental formulation 3) do not contain active ingredients but only excipients. Experimental formulation 2 will contain 1% (w/v) Betaine (derived from coconut oil), which is an excipient and not an active. Betaine is an alternative and milder detergent than sodium lauryl sulphate usually used in toothpaste. Experimental formulation 3, the other placebo, will not contain Betaine but will contain the detergent sodium lauryl sulphate instead (also an excipient and not an active). Participants will be randomly allocated to one of the dentrifice slurries during each treatment period and cross over to another dentrifice slurry for the following treatment period. Each participant will rinse with all five dentrifice slurries over the study period. Therefore, participants will complete five 14-day treatment periods each separated by a one-week washout period during which the participants will rest from the study. The entire study period will comprise a total of 14 weeks in total. Tubes containing 5 mL of 10% sucrose and tubes containing 5 mL of dentrifice slurry both diluted in distilled de-ionized water and prepared by the research team, will be given to the participants by the research team. The sucrose solutions will also be filtered by the research team prior to being dispensed. The dentrifice slurries will be prepared by diluting 1 gram of dentrifice in 4 mL of distilled de-ionized water. Four times a day on each day of each treatment period, when wearing their appliances, participants will rinse with the sucrose solutions and dentrifice slurries as follows. At 9:30 am, 11:00 am, 1:30 pm and 3:30 pm, participants will rinse with all 5 mL of the sucrose solution in one of the tubes for 60 seconds. Participants will then expectorate the sucrose solution and then, 40 minutes later (at 10:10 am, 11:40 am, 2:10 pm and 4:10 pm), they will shake a tube containing their allocated dentrifice slurry and immediately rinse with all 5 mL of the slurry for 60 seconds. They will then expectorate the slurry and continue wearing their appliance. On weekdays, the solutions and slurries will be stored at room temperature. On weekends, the solutions and slurries will be stored in a refrigerator at home and participants will be instructed to allow the solutions and slurries to warm to room temperature prior to rinsing. During the treatment periods, participants will only leave their appliances out of their mouths when eating, drinking (except water), and when brushing their teeth and cleaning their appliance twice a day as instructed. Participants will brush their teeth with a standard fluoride toothpaste (supplied) twice daily. They will clean their appliance using a toothbrush and fluoride-free toothpaste (both supplied) and then rinse their appliance with distilled de-ionized water (supplied). They will be instructed to avoid brushing or rinsing the troughs holding the enamel and dentine slabs. When the appliances are removed they will be placed in snap-sealed bags (supplied) with several drops of distilled de-ionized water (supplied) to prevent them drying. Participants will be asked to not use any toothpaste other than the fluoride toothpaste given to them by the research team and will be asked to refrain from using any mouthrinses (other than the sucrose solutions and allocated dentrifice slurries at the specified times) for the duration of the study. They will also be instructed to refrain from consuming antibacterial mints or lozenges or chewing any gum products during the entire study period. Participants will otherwise maintain normal dietary and oral hygiene practices during the study period. Participants will also provide 15 post-rinse saliva samples during the study by expectorating the dentrifice slurry and accumulated saliva immediately after one of the rinses with the slurries on three different weekdays during each treatment period. Each participant will be requested to inform the research staff if they experience any discomfort wearing the appliance. The qualified dentist on the research team will then assess the problem and adjust the appliance if needed. All participants will be given a diary at the commencement of each treatment period and will be asked to fill in the times they wear the appliance and rinse with the sucrose solutions and dentrifice slurries. Participants will also be asked to inform the research team of any adverse events that occur during the treatment periods and note these in the diary. Following the initial screening dental examination, participants will be examined ten times by a qualified dentist on the research team over the course of the study period. These will comprise five dental examinations at the start of each treatment period and five dental examinations at the completion of each treatment period. These examinations, will be conducted to ensure no dental caries or periodontal disease is present. Again, no radiographs will be taken during any of these examinations. After the final dental examination at the end of final treatment period, participants will be given the option of having a standard fluoride treatment (fluoride gel in trays) administered by the qualified dentist. Participants will be assured they will be free to withdraw from the study at any time without prejudice.