Enamel Remineralization Under Biofilm via Adhesive Containing Amorphous-calcium-phosphate-nanoparticles

Objectives: Dental caries, one of the most prevalent diseases worldwide, is a biofilm-dependent condition mainly due to Streptococcus mutans. The cariogenic biofilm, colonizing on enamel, restoration and bonding interface, limits the longevity of composite. The remineralization of enamel around adhesive interface contributes to protecting the bonding interface and reducing restoration failure. The aim of this study was to investigate enamel remineralization in a stimulated oral biofilm environment via an adhesive containing nanoparticles of amorphous calcium phosphate (NACP).
Methods: The enamel blocks were immersed in demineralization solution (pH 4.5, 37 °C) for 72 hours to imitate initial carious lesion. After that, the demineralized samples were subjected to a Streptococcus mutans biofilm for 24 hours. Specimens with biofilm were then divided into group without adhesive, group with commercial fluoride-releasing adhesive, and group with NACP adhesive. All blocks next underwent 3-hour demineralization in brain heart infusion broth with sucrose (BHIS) and 27-hour remineralization in artificial saliva (AS), simulating daily pH falling during the meal and rising after the meal. The pH of BHIS and Ca, P content in AS was measured every day. After 7-day cycling, lactic acid production, colony-forming unit (CFU) count, and Ca, P content in biofilm were evaluated. The remineralization effectiveness of enamel was analyzed by transverse microradiography (TMR), surface microhardness testing of vertical section, and scanning electron microscopy (SEM).
Results: The NACP adhesive released abundant Ca and P, achieved acid neutralization, reduced lactic acid production, lowered CFU count. Better remineralization effectiveness was observed in group treated with NACP adhesive.
Conclusions: The NACP adhesive functioned well in remineralizing initial enamel lesion with cariogenic biofilm. It is promising to be applied to preventing secondary caries and prolonging the longevity of restoration.