The effect of silver diamine fluoride and sodium fluoride varnish on salivary ph, streptococcus mutans, and lactobacillus counts in early childhood caries: a randomized controlled trial

Recently there has been interest in Silver Diamine Fluoride (SDF) as a method for caries prevention, however there are lacking clinical study on the antibacterial efficacy. This randomized controlled trial study aimed to compare the effect of 38% SDF and 5% Sodium Fluoride (NaF) varnish on the salivary pH, Streptococcus mutans (S. mutans) and Lactobacillus counts in children with Early Childhood Caries (ECC). Sixty healthy children aged 4 to 6 years with active dentin caries (ICDAS code 5) in deciduous teeth were randomly assigned to treatment. Baseline unstimulated saliva was collected, followed by the application of the agents. After three months, saliva samples were recollected. S. mutans and Lactobacillus counts were evaluated using CFU/ml. The salivary pH and S. mutans and Lactobacillus counts were compared using a paired t- test. The comparison of 3 months treatment with 38% SDF and 5% NaF were analysed with repeated measures ANOVA. The presence and counts of S. mutans and Lactobacillus acidophilus (L. acidophilus) were then confirmed with quantitative Polymerase Chain Reaction (qPCR). Twenty-three and twenty-six children were enrolled in the SDF and NaF treatment respectively, with a total 11 dropped out children. Five o f them were uncontactable, while six failed to attend the follow-up appointment. Mean age was 4.49 ±0.65 years, and more than half of the participants were boys. At the three months follow-up, both groups showed a significant increase of mean difference salivary pH in 38% SDF (0.71 ±0.24) and 5% NaF group (0.18 ±0.18). There was also significant decrease from baseline bacterial counts of 5. mutans counts in 38% SDF (109.39 ±36.46) and 5% NaF group (25.35 ±28.09). Lactobacillus counts also significantly decrease from baseline in 38% SDF (9.65 ±4.94) and 5% NaF (1.23 ±1.37). However, there was a significant difference in the increase in salivary pH between 38% SDF and 5% NaF (10.19% and 2.56% respectively), reduction of S. mutans (66.05% and 16.21 % respectively) (PO.OOl), and reduction Lactobacillus (45.20% and 6.37 % respectively) (P<0.005). qPCR confirmed the reduction of L. acidophilus in the 38% SDF compared to the 5% NaF group. This study acknowledges several limitations, including unexamined confounding factors, single-center data limiting generalizability, and the absence of long-term antimicrobial effect assessment for SDF. In conclusion, the antibacterial efficacy of 38% SDF was superior to 5% NaF in reducing S. mutans and L. acidophilus level simultaneously, reducing the salivary pH acidity.