Remineralization of demineralized enamel via calcium phosphate nanocomposite

Secondary caries remains the main problem limiting the longevity of composite restorations. The objective of this study was to investigate the remineralization of demineralized human enamel in vitro via a nanocomposite containing nanoparticles of amorphous calcium phosphate (NACP). NACP were synthesized by a spray-drying technique and incorporated into a dental resin. First, caries-like subsurface enamel lesions were created via an acidic solution. Then, NACP nanocomposite or a commercial fluoride-releasing control composite was placed on the demineralized enamel, along with control enamel without a composite. These specimens were then treated with a cyclic demineralization/remineralization regimen for 30 days. Quantitative microradiography showed typical enamel subsurface demineralization before cyclic demineralization/remineralization treatment, and significant remineralization in enamel under the NACP nanocomposite after the demineralization/remineralization treatment. The NACP nanocomposite had the highest enamel remineralization (mean ± SD; n = 6) of 21.8 ± 3.7%, significantly higher than the 5.7 ± 6.9% for fluoride-releasing composite (p < 0.05). The enamel group without composite had further demineralization of -26.1 ± 16.2%. In conclusion, a novel NACP nanocomposite was effective in remineralizing enamel lesions in vitro. Its enamel remineralization was 4-fold that of a fluoride-releasing composite control. Combined with the good mechanical and acid-neutralization properties reported earlier, the new NACP nanocomposite is promising for remineralization of demineralized tooth structures.