Effects of silver-diamine fluoride on caries-like lesion and cariogenic biofilm

Abstract

OBJECTIVES: To characterize the effects of silver diamine fluoride (SDF) on caries-like lesion and a multi-species cariogenic biofilm in an artificial mouth. METHODS: Caries-like lesions were created by demineralizing human dentin blocks prepared from extracted sound third molars (IRB-UW08-052). Multi-species cariogenic biofilm was formed on caries-like lesions using common cariogenic bacterial species, namely Streptococcus mutans, Streptococcus sobrinus, Lactobacillus acidophilus, Lactobacillus rhamnosus, and Actinomyces naeslundii in artificial mouth for 7 days. The infected caries-like lesions were divided into two groups. SDF was applied in the treatment group while water was used as control. All the samples were put into artificial mouth for 21 days. Microbial growth kinetics, architecture, viability and distribution were evaluated using colony forming units (CFU), scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Mineral and organic content of caries lesions were evaluated with microhardness testing and Fourier Transform Infra-Red Spectroscopy (FTIR). RESULTS: Total log bacterial counts of SDF-treated group were 0.65±0.71, 4.94±0.07 and 5.72±0.19 compared to 9.38±0.17, 9.28±0.23 and 9.34±0.06 in the control group at day 7, 14 and 21 respectively (p<0.01). SEM and CLSM observations showed confluent cariogenic biofilm in the control group whilst less bacterial growth in the SDF-treated samples. Microhardness of SDF-treated lesions in the outmost 100ìm was significantly higher than the control (p<0.05). The log [Amide I : HPO42-] in SDF treated lesion was 0.28±0.06, 0.22±0.06 and 0.12±0.11 compared to 0.46±0.05, 0.83±0.36 and 1.34±0.31 in the control group at day 7, 14 and 21 respectively (p<0.01); showing significantly less collagen I breakdown from SDF-treated lesions than the control. CONCLUSION: SDF treatment inhibits multi-species cariogenic biofilm formation on caries-like lesion. It also hardens the surface of caries-like lesions and reduces collagen breakdown of dentin.