The literature recognizes that fluoride is the most widely used and studied means for dental remineralization. The use of fluoride toothpaste in brushing is considered more rational method for the prevention of caries. However, the current challenge of toothpaste is the substantivity, so new compounds have been introduced into these formulations. This study aims to evaluate the in vivo effect of fluoride dentifrice containing nanoencapsulated Fluoride (Nano-F) - in fluoride retention in saliva and dental plaque. A study of the clinical and laboratory type, crossover, double-blind, randomized will be held. After sample calculation, the total of 12 individuals aged between 18 and 35 years old, healthy, decayed, missing, and filled teeth index less than 6 and residents in brazilian northeast capital will be part of the sample. Fluoride bioavailability will be evaluated in the biofilm and saliva after the use of fluoridated weekly. The biofilm will be assessed on 1h and 12 h after brushing; and unstimulated saliva in times of 3, 15, 30, 45, 60 minutes and 12 hours after. It will be 3 toothpastes: 50% Nanoencapsulated Fluoride, 100% Nanoencapsulated Fluoride and Free sodium fluoride. Between weeks of use, brushing will be extended washout (without fluoride) to avoid carryover effect. inferential data analysis will be carried out, considering the amount of alpha <0.05. So knowing that caries is a dynamic process, the largest fluoride retention in the oral fluids promoted by the Nanoencapsulated Fluoride may have important impact on Des-Re process and in the control of dental caries

1. Study design It is a quantitative study of double-blind randomized crossover clinical type with inductive approach and documentation of technical and direct observation with measurements in the laboratory.

   In order to assess the bioavailability of intraoral fluoride week after the use of fluoride toothpastes containing Nanoencapsulated Fluoride, it will be collected biofilm samples 1h and 12 h after brushing; and unstimulated saliva in times of 3, 15, 30, 45, 60 minutes and 12 hours after. The data will be obtained by physical and chemical analysis of the samples of fluoride (F). Therefore, the study will consist of two interrelated steps: a clinical phase for biofilm collection and saliva; and laboratory stage for fluoride analysis in the samples.

   Will be conducted pilot test with three participants before the start of the study.

2. Sample Size The sample size calculation was performed using fluoride concentration data in dental biofilm previous study and taking effect size difference between the experimental dentifrice (100% Nanoencapsulated Fluoride ) and positive control of at least 3.4 ppm of F- in biofilm after 12 hours, namely, 25%. Admitting experimental protocol with beta error of 10% alpha error of 5%, one-tailed and statistical power of 90%, the sample size was calculated for 6 people. For the calculation we used the Excel software and mathematical formula for clinical trials of superiority given. Adding sample loss resulted in 12 people.

3. Experimental Dentifrice For this study will be used four toothpastes: 50% Nanoencapsulated Fluoride, 100% Nanoencapsulated Fluoride, Free sodium fluoride, Without fluoride. The toothpaste, made available by the company from Brazil are packed in the same packaging and have the taste of mint. Except wash out the tubes with toothpaste will be identified by letters (A, B and C) by an independent researcher. The letters code will not be revealed to the participants nor the researcher who will accompany them. These will be drawn at random for daily use for seven days in four times, giving an interval of one week wash-out between them.

   In these periods of wash-out will use a toothpaste without fluoride. In the end, all study participants will use the 5 experimental dentifrice at different times.

4. Clinical phase The participant will be informed about the study and after its acceptance, he/she will initiate the study. Initially will be clinical examination in order to report the presence of any of the exclusion criteria already listed. After verifying the absence of these criteria, there will be a dental prophylaxis pumice for removal of this biofilm and in some cases may be made supragingival scraping. The patient will be advised not to make use of any fluoride product during the experiment. At first, volunteers are instructed to use a toothpaste without fluoride (wash out) the first week, in order to equate the study participants and eliminate any potential carryover effects of toothpaste used previously.

   The participant will get a tube of toothpaste and will be instructed to brush their teeth for 1 minute and rinse with 10 mL of water twice a day (morning and night). On the seventh day, the participant will be instructed to brush only the occlusal surfaces of your teeth, to allow biofilm accumulation of flat surfaces. When going to bed, you are warned not to eat or drink (except water) as well as not brushing your teeth until the next day. On the following morning, approximately 12 hours after the last brushing and fasting, the first dental biofilm sample and unstimulated saliva is collected. It will be used to remove biofilm Hollenback vestibular faces, interproximal, palatal and lingual right hemiarch and deposited in a pre-weighed Eppendorf tube in an analytical balance. To saliva collection, the participant, at rest, will be instructed to spit for a minute in a graduated glass tube. After that, the participant will brush the occlusal surfaces for 1 min and rinse with 10 mL of water. Soon after, will new collection of saliva and plaque. Saliva samples will give up in times of 3, 15, 30, 45 and 60 minutes after brushing, while the biofilm left hemiarch will be collected one hour after brushing. After the collection will be offered at breakfast organized by researchers participating in the crown of that research center.

5. Laboratorial phase Samples will be evaluated through physical-chemical analysis of fluoride using calibrated fluoride electrode. Samples will be analyzed for fluoride concentration using ion-specific electrode after diffusion facilitated with hexamethyl disiloxane (HMDS). The calibration curve is made for each analysis. All analyzes will be done in triplicate and be submitted for validation.

6. Data analysis The study data will be analyzed by inferential statistics considering p <0.05.

Inclusion Criteria:

• resident in João Pessoa
• Decayed, Missing, Filled Index<6
• Healthy

Exclusion Criteria:

• orthodontic treatment
• gingivitis
• Periodontal disease
• Smokers
• Present active tooth decay
• Tooth sensitivity
• Those undergoing treatment with fluoride products and / or use of antimicrobials in the past four weeks