Objective: This in-vitro study evaluated the remineralizing effect of nano-pearl and nano-seashell incorporated into fluoride-based pits-and-fissures sealants by assessing the enamel surface microhardness and the enamel elemental analysis.  
Materials and Methods: 75 extracted third molars were randomly allocated to one of the following 5 groups of fluoride containing sealant: 10% nano-pearl; 15% nano-pearl; 10% nano-seashell; 15% nano-seashell; or plain fluoride containing sealant. After 2 weeks of dynamic pH-cycling using Pepsi as demineralizing solution; 10 molars of each group were subjected to microhardness assessment, while 5 molars of each group were subjected to Energy Dispersive X-ray Analysis.
Results: Teeth treated with 15% nano-pearl reported the highest percentage increase (20.5%) while teeth treated with plain fluoride containing sealant showed a percentage decrease (-11.62 %). The XRD pattern results confirmed the presence of aragonite and calcite polymorphs of CaCO₃ in nano-pearl powder and the presence of aragonite in nano-seashell powder. Calcium ions recorded a significantly higher value in the groups treated with 10% and 15% nano-pearl incorporated pits and fissure sealant.
Conclusion: The incorporation of 10 % and 15 % nano-pearl and nano-seashell particles into fluoride-based pits and fissure sealant significantly improved the enamel surface microhardness as well as the enamel mineral content.