The effect of gels containing high concentrations of calcium with and without fluoride on the cosmetic appearance of white spots on tooth enamel and tooth sensitivity.

This randomized controlled study will use a double-blind, four-way crossover design to assess the effects of topical application of two gels, one solution, and not applying either gel or solution, on the cosmetic appearance of white spot lesions on enamel surfaces (early enamel decay) and occlusion of open dentinal tubules in tooth root dentine, using an established intra-oral caries model. Four human volunteers will be selected 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. The enamel slabs will contain subsurface lesions created in the laboratory and the dentine slabs will have open tubules. The appliances will be fabricated under the direct supervision of a registered prosthetist/dental technician at the Royal Dental Hospital of Melbourne. Though participants were not recruited on the basis that they had participated in previous in situ studies, at least some of the participants had recently participated in an in situ study registered with the ANZCTR (ACTRN12620000747921) and all had participated in other studies not registered with the ANZCTR. A qualified dentist on the research team will ensure the appliance fits correctly one week prior to commencement of the first intervention in this project. The enamel and dentine slabs will be also be attached to the appliances by the research team one week prior to the first intervention in this project. Participants will wear the appliances for 24 hours a day over four 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. One of four treatments will each be randomly allocated to one of the four treatment periods. For three treatments, a gel or solution will be applied to the surfaces of each slab on the appliance. For the fourth treatment nothing will be applied to the slabs. The three treatments applied to the slabs will be: 1) gel containing 60% (w/v) casein phosphopeptide-amorphous calcium phosphate and 1100 mg/L fluoride as stannous fluoride; 2) gel containing 60% (w/v) casein phosphopeptide-amorphous calcium phosphate but not containing stannous fluoride; 3) solution containing 1100 mg/L fluoride as stannous fluoride. The solution will be the positive control for the gels. The fourth treatment where neither gel nor solution is applied to the slabs on the appliance will be the negative control. The gels will be prepared by the research team using distilled de-ionized water and will be slightly alkaline when prepared so will have a small amount of dilute hydrochloric acid added by the research team to bring the pH to 7.0. Therefore, the gels will contain a small concentration of chloride ions. The stannous fluoride solution will also be prepared by the research team using distilled de-ionized water. It will have a pH of approximately 4.0 and will not have its pH adjusted to 7.0 due to precipitation of stannous hydroxide ions when hydroxide ions are added so will only contain stannous fluoride in distilled de-ionized water. For each of the three treatment periods a gel or the solution is allocated, once each weekday participants will present to the research department at the Melbourne Dental School and give their appliances to the research team who will paint one of the gels or the solution on the surface of each slab on the appliance and then heat the gel or solution on the slabs using a white light used in clinical dental practice to set white filling materials. This will all be done with the appliance out of participants' mouths. Once the gel or solution has cooled, the appliance will be returned to the participants for them to wear again. Each participant will wait approximately 10 to 15 minutes during each visit the gel or solution is applied to the slabs. During the treatment period that no gel or solution is applied to the slabs on the appliance, participants will not need to attend the research department at the Melbourne Dental School on those days. Participants will be instructed not to drink water with the appliance in their mouth within 40 minutes of the gel or solution being applied to the slabs. The research team will prepare the gels and solution every second day using distilled de-ionized water, will store the gels and the solution in a secure refrigerator in the research department, and will be experienced in painting and heating the gels and the solution on the slabs. During each of the two weekends during the three treatment periods a gel or the solution is allocated, participants will paint their allocated gel or solution on the slabs at home once on Saturday and once on Sunday. They will be given tubes of their allocated gel or solution in tubes by the research team on the preceding Fridays and will be instructed to keep the tubes in a refrigerator at home when not being used. Once on each of the two weekend days, prior to painting their allocated gel or solution on the slabs, participants will remove a tube of gel or solution from their refrigerator and allow it to warm to room temperature. They will then remove their appliance, rinse it briefly with distilled de-ionized water (supplied), and then paint the gel or solution on the surface of the slabs as instructed by the research team but will not heat the gel or solution. All the gel or solution in the tube (no more than 1 mL) will be painted on the surface of the slabs by the participants each time using a small brush used in clinical dentistry to apply solutions or gels to teeth. After the gel or solution is painted on the slabs by the participants on weekends, participants will then insert their appliances into their mouths. As for weekdays, participants will be instructed not to drink water with the appliance in their mouth within 40 minutes of the gel or solution being applied to the slabs on weekends. During the fourth treatment when neither gel nor solution is painted on the slabs, participants will wear their appliance in exactly the same way as they will wear their appliance during the other three treatment periods. Participants will be randomly allocated to one of the four treatments during each treatment period and cross over to another treatment for the following treatment period. Each participant will complete all four 14-day treatment periods. The entire study period, including rest periods, will comprise a total of 11 weeks in total. The order of treatments allocated to each participant will be unknown to the researchers analyzing the results. Participants will not know the identities of the two gels. During the treatment periods, participants will only leave their appliances out of their mouths when eating, drinking (except water), when brushing their teeth and cleaning their appliance twice a day as instructed, or when participating in sporting activities. 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 the enamel and dentine slabs but will be instructed to rinse the slabs with distilled de-ionized water (supplied). 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 standard fluoride toothpaste given to them by the research team and will be asked to refrain from using any mouthrinses for the duration of the study. Participants will otherwise maintain normal dietary and oral hygiene practices during the study 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 remove the appliance and, if applicable to that treatment period, when the gel or solution is painted on the slabs on their appliance. 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. They will return the diary at the conclusion of each treatment period. Following the initial screening dental examination, participants will be examined eight times by a qualified dentist on the research team over the course of the study period. These will comprise four dental examinations at the start of each treatment period and four 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 fourth 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.