The use of specific remineralizing agents in toothpastes may help to prevent caries and treat dentinal sensitivity. In this study, applied nanotechnologies were used to develop a filler for toothpastes with remineralizing properties. Carbonate hydroxyapatite nanocrystals, with size, morphology, chemical composition and crystallinity comparable with that of dentine, were synthesized in mild condition. The remineralizing effect was studied with a scanning electron microscopy putting materials onto the slices of dentine previously demineralized with ortophosphoric acid. The application of the materials showed the progressive closure of the tubular openings of the dentine with plugs within 10 minutes and a regeneration of a surface mineral layer within 6 hours. This rates of remineralization seems to be compatible with the development of toothpastes with remineralizing effect.