Effect of silver fluoride on micro-ecology of plaque from extensive caries of primary teeth - in vitro study

Background: The action mechanism of silver diammine fluoride (SDF) on plaque micro-ecology was seldom studied. This study investigated micro-ecological changes in dental plaque on extensive carious cavity of deciduous teeth after topical SDF treatment. Methods Deciduous teeth with extensive caries freshly removed from school children were collected in clinic. After initial plaque collection, each cavity was topically treated with 38% SDF in vitro. Repeated plaque collections were done at 24 hours and 1 week post-intervention. Post-intervention micro-ecological changes including microbial diversity, microbial metabolism function as well as inter-microbial connections were analyzed and compared after Pyrosequencing of the DNA from the plaque sample using Illumina MiSeq platform. Results After SDF application, microbial diversity decreased (p>0.05). Microbial community composition post-intervention was obviously different from that of supragingival and pre-intervention plaque as well as saliva. At 1 week post-intervention, the relative content of Pseudomonas , Fusobacterium and Pseudoramibacter was obviously higher than before, while most of the other bacteria was obviously reduced, although not statistically significant (P>0.05). The inter-microbial connections became more complex, with positive connections overcame negative ones. Carbohydrate transportation and metabolic functions in the plaque were significantly reduced at 24 hours and 1 week post-intervention. Conclusions SDF has extensive antimicrobial effect on dental plaque, which may reduce carbohydrate metabolism in dental plaque and help promote new balance of the plaque flora.