Objectives: This clinical study was conducted to evaluate the efficiency of nano-hydroxyapatite (n-HAp) in reducing dentin hypersensitivity individually or combined with fluoride. Materials and methods: Forty hypersensitive teeth from 10 patients with hypersensitive symptoms were treated using hydroxyapatite nanoparticles (nHAp) gel at different concentrations/ sodium fluoride (NaF) containing according to four treatment groups: Group 1; 15% nHAp + 1% NaF, Group 2; 15% nHAp, Group 3;
25% nHAp+ 1% NaF, Group 4; 25% nHAp. The initial sensitivity levels were recorded using a verbal rating scale (VRS) and visual analogue scale (VAS) at the baseline visit. The responses were evaluated at 0, 1 day, 1, 2 and 4 weeks respectively for all groups. Results: There was a high statistical significant differences between pain scores before and after treatment for all treated groups. There was statistically significantly high difference between 25% nHAp and the other groups, as they need 4 applications for complete relief while 25% nHAp needs only 3 applications. Conclusion: Nano-hydroxyapatite with 25% concentration was the most effective in alleviating the hypersensitivity symptoms.