A total of 26 volunteer patients with at least 2 non-cavitated molar teeth will be assigned in this study. Patients will be divided into two groups according to type of flowable composite (R) where groups R1 the pits and fissure will be sealed with Hydroxyapatite Nanofiber reinforced flowable composite while groups R2 the pits and fissure will be sealed with conventional resin-based flowable composite. Each restoration will be assessed after one week, six and twelve months Both materials will be applied according to manufacturer's instructions where teeth should be cleaned to remove surface stains, then select appropriate shade of the flowable composite, A rubber dam is the preferred method of isolation, etch and rinse adhesive system is applied, where acid etching will be applied for 15 seconds then rinse and dry followed by application of adhesive then light cure 10 seconds, then place and cure in 2 mm increments of the flowable composite for 20 s., gently remove oxygen inhibition layer after light cure with slurry of pumice or polishing paste All restorations were reviewed after 1 week, 6, 12 months by two investigators who were blinded to the material used for the restorations. All restorations were be evaluated by calibrated examiners following the FDI criteria