Silver-diamine-fluoride on dentine infected with Streptococcus mutans and Lactobacillus acidophilus

Abstract

OBJECTIVES: To characterize the effects of silver diamine fluoride (SDF) on dentine carious lesion infected with Streptococcus mutans (SM) and Lactobacillus acidophilus (LA) dual-species biofilm. METHODS: Twenty-four artificially demineralized human dentine blocks were inoculated with SM and LA biofilm for 2 days. Twelve blocks received topical SDF application (test group), and another 12 received water (control group). After incubation at 37°C in microplate anaerobically for 7 days, the biofilms were evaluated for microbial kinetics, morphology and viability by colony forming units (CFU), scanning electron microscopy (SEM), and confocal microscopy, respectively. The dentine carious lesions underwent microhardness assessment, elemental analysis by energy-dispersive x-ray spectroscopy, and mineral to organic content assessment by Fourier transform infrared spectroscopy. RESULTS: The bacterial counts of SM and LA in the test group were 4.02±0.35 and 4.00±0.71 CFU, respectively; compared to 4.79±0.31 and 6.72±0.49 CFU in the control group, respectively (p<0.05). SEM and confocal microscopy observations showed confluent SM and LA biofilm in the control group, but not in the SDF-treated biofilms. Microhardness and weight percentages of calcium, phosphorus and fluoride of SDF-treated lesion surface were significantly higher than those of the control (p<0.05). The log [Amide I: HPO42-] for test and control groups were 0.31±0.10 and 0.57±0.13 (p<0.05) respectively, suggesting more Type-1 collagen content in the test group than in the control group. CONCLUSION: This study showed an anti-microbial activity of SDF against the SM and LA biofilms on infected dentine. Furthermore, SDF slowed down demineralization of dentine under a biofilm.