Long-term dentin Remineralization by PAMAM and NACP Adhesive

Objectives: The objective of this study was to investigate the long-term dentin remineralization capability of the combination of poly(amido amine) (PAMAM) with rechargeable adhesive containing nanoparticles of amorphous calcium phosphate (NACP) for the first time.
Methods: NACP adhesive was immersed in lactic acid solution at pH 4 to exhaust its calcium (Ca) and phosphate (P) ion release, and then recharged with Ca and P ions. Dentin samples were pre-demineralized with 37% phosphoric acid, and then divided into four groups: (1) dentin control, (2) dentin treated with PAMAM, (3) dentin with recharged NACP adhesive, (4) dentin with PAMAM+recharged-NACP adhesive. In group (2) and (4), PAMAM-coated dentin was immersed in phosphate-buffered saline with a heavy shaking action for 77 days to accelerate the detaching of PAMAM macromolecules from demineralized dentin. Samples were treated with cyclic remineralization/demineralization regimen for 21 and 35 days.
Results: After 77 days of fluid flow challenge, the immersed-PAMAM achieved a moderate remineralization, with small amount of minerals precipitated on dentin surface and in dentinal tubules. The recharged NACP adhesive re-released Ca and P ions with a concentration of about 2.7 and 1.5 mmol/L from 1 to 21 d, respectively (n=6). Besides, the recharged NACP adhesive raised the pH from 4 to 5.6 and 6.1 in 15 and 60 min from 1 to 21 d, respectively (n=6). Sparkly, the immersed-PAMAM+recharged-NACP adhesive achieved long-term dentin remineralization, with the most minerals regeneration and the greatest dentin hardness increasing, which was approached the level of healthy dentin (n=6; p>0.1).
Conclusions: The excellent long-term remineralization capability of PAMAM+NACP adhesive on demineralized dentin was demonstrated for the first time. The novel PAMAM+NACP adhesive achieved great triple benefits: stable nucleation templates, sustained ions release and continuous acid-neutralization. The combination is promising to provide long-term bond-protection and caries-inhibition, and prolong the longevity of restoration.