New biomimetic carbonate-hydroxyapatite nanocrystals (CHA) have been designed and synthesized in order to obtain a remineralization of the altered enamel surfaces. Synthesized CHA mimic for composition, structure, nano dimension and morphology bone apatite crystals and their chemical-physical properties resemble closely those exhibited by enamel natural apatite. CHA can chemically bound themselves on the surface of natural enamel apatite thanks to their tailored biomimetic characteristics. The remineralization effect induced by CHA represents a real new deposition of carbonate-hydroxyapatite into the eroded enamel surface scratches forming a persistent biomimetic mineral coating, which covers and safeguards the enamel structure. The experimental results point out the possibility to use materials alternative to fluoride compounds which is commonly utilized to contrast the mechanical abrasions and acid attacks. The apatitic synthetic coating is less crystalline than enamel natural apatite, but consists of a new biomimetic apatitic mineral deposition which progressively fills the surface scratches. Therefore the application of biomimetic CHA may be considered an innovative approach to contrast the acid and bacteria attacks.

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.

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We have synthesized citrate-stabilized amorphous calcium phosphates doped with fluoride (F-ACP), strontium (Sr-ACP), and zinc (Zn-ACP) ions. ACP based materials were proven to have excellent remineralizing action on demineralized dental hard tissues while F−, Sr2+, and Zn2+ ions are known to have antimicrobial activity, so the aim of our work was to produce multipurpose materials for preventive dentistry that inhibit cariogenic bacteria and remineralize dental enamel and dentin. Doping ions were successfully incorporated into ACP up to 2 wt.% F− and 12 wt.% Sr2+ or Zn2+ without altering ACP physical-chemical properties. Evaluation of viability of Streptococcus Mutans biofilm treated with ion-doped ACP materials showed that F-ACP and Sr-ACP have a direct inhibitory effect while Zn-ACP has a negligible effect. The different antibacterial activity was correlated to the ion-release properties of the materials, as in conditions mimicking a cariogenic environment F-ACP and Sr-ACP have a release of ca. 5–7% of total F− or Sr2+ while only ca. 1% of total Zn2+ is released. All ion-doped ACP materials are able to remineralize in vitro demineralized human enamel slabs by epitaxial deposition of a new ion-doped crystalline phase in direct contact with the pristine one. Enamel slabs remineralized with F-ACP has an antibacterial/bacteriostatic action, proving that F-ACP acts as preventive antimicrobial agent. Overall, our work demonstrates the high potential of ACP doped with antibacterial ions for the preventive treatment of dental caries.