Nano-Hydroxiapatite Doped Resin Infiltrant Penetration and Anti-Biofilm Effect

Objectives: This study evaluated the anti-biofilm effect of a resin infiltrant (RI) containing amorphous nanohydroxyapatite (AHp) or in rod form (RHp) on the composition of the biofilm formed in situ over artificial initial caries lesions (AICL). In addition, the penetration capacity of the AHp- and RHp-doped infiltrants was compared with that of the resin-based infiltrant in shallow artificial caries lesions.
Methods: Sixteen subjects used intraoral devices containing AICL blocks infiltrated with RI-base, RIAHp or RIRHp. The samples were exposed to 20% sucrose (8x/day). Biofilm composition was assessed by counting colony forming units (CFU) of total microorganisms, total streptococci, S. mutans and lactobacilli. Enamel blocks with AICL were conditioned with phosphoric acid, stained with rhodamine, and infiltrated according to the groups. Dental sections of 1 mm thickness were stained with sodium fluorescein and analyzed by confocal microscopy to obtain infiltration index and penetration depth (PD) using ImageJ software. ANOVA/Tukey and Kruskal-Wallis tests were used.
Results: No difference in viability and biofilm composition was found between the groups (p>0.05). The infiltration index values showed no statistical differences between the groups, but the PD for RIRHp (33.79±10.10 mm) was significantly lower (p<0.050) than for RI-base (53.90±10.02 mm) and for RIAHp (49.46±8.30 mm).
Conclusions: It is concluded that amorphous nanohydroxyapatite had no antimicrobial effect on cariogenic biofilm formed in situ, but its remineralizing effect can be achieved since its addition to infiltrants did not compromise the penetration depth of the infiltrant.