Inhibition of dentine caries using fluoride solution with silver nanoparticles: An in vitro study

Objectives: To investigate the remineralising and staining effects of sodium fluoride (NaF) with silver nanoparticles (AgNPs) on artificial dentine caries. Methods: Human dentine blocks with artificial caries were divided into four groups. Group 1 received 5 % NaF (22,600 ppm fluoride) with 4000 ppm AgNPs; group 2 received 4000 ppm AgNPs; group 3 received 5 % NaF, group 4 received deionised water (negative control). All groups underwent three biochemical cycles. Each cycle included Streptococcus mutans biofilm challenge and remineralisation process. The lesion depth, mineral-organic content, surface morphology and crystal characteristics of dentine blocks were evaluated using micro-computed tomography, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction. Colour change of dentine blocks was assessed using spectrophotometry. Results: The mean lesion depths of groups 1-4 were 151.13 +/- 29.13 mu m, 172.38 +/- 23.44 mu m, 190.41 +/- 32.81 mu m and 221.24 +/- 27.91 mu m, respectively. The hydrogen phosphate-to-amide I ratios of groups 1-4 were 5.98 +/- 0.36, 3.86 +/- 0.56, 4.00 +/- 0.67 and 2.53 +/- 0.40, respectively. There was no significant interaction effect between AgNPs and NaF. SEM showed less exposure of dentine collagen fibres in group 1 when compared to other groups. X-ray diffraction revealed presence of silver chloride and metallic silver in group 1 and 2. There was no significant difference in colour change among the four groups (p = 0.74). Conclusions: NaF solution with AgNPs can remineralise dentine caries without staining. Clinical Significance: Sodium fluoride solutions that include silver nanoparticles have potential uses in the management of caries.