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 (1100 ppm F with hydrocolloid) 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.