How do different topical fluoride applications affect salivary and plaque fluoride levels for young children with dental caries?

A COMMENTARY ON: Asavalertpalakorn C, Jirarattanasopha V, Nakornchai S, Horsophonphong S. Plaque and salivary fluoride levels in preschoolers following applications of silver diamine fluoride, sodium fluoride varnish, and their combination: a randomized clinical trial. Int J Paediatr Dent. 2026;36:81-9. https://doi.org/10.1111/ipd.70030 . DESIGN: A three-arm randomised controlled trial compared the salivary and plaque fluoride levels for young children, following application of different fluoride prevention and treatment procedures (silver diamine fluoride, sodium fluoride varnish and silver diamine fluoride and sodium fluoride varnish together), in child development centres in Thailand. CASE SELECTION: Children aged 3-6 were selected who had at least one carious tooth reaching dentine in the primary dentition. Included children were considered healthy and co-operative. Children who had received professional fluoride application within the last three months were excluded, or those with a known allergy to any component. Twenty children were randomised to each group. Group 1 received silver diamine fluoride application (1 drop) to dentinal carious lesions; group 2 received sodium fluoride varnish application (0.25 ml) to all erupted primary teeth; group 3 received both the silver diamine fluoride and sodium fluoride varnish interventions. Fluoride applications were not applied to pulpally involved teeth. DATA ANALYSIS: Plaque and saliva samples were collected at baseline (prior to fluoride application), at 5, 30 and 60 minutes, and at 24 and 48 hours. Kruskal-Wallis and Friedman tests were used to compare the 3 groups at the various time points. A Bonferroni correction was applied to account for the multiple comparisons. RESULTS: In total, 60 children were randomised, data were analysed for 50 children's salivary samples and 49 children's plaque samples. The mean age was 3.7 months, with children having a mean of 7.6 decayed, missing or filled teeth. At the shorter-term (5, 30 and 60 minute) time points, the salivary fluoride levels were significantly higher in the sodium fluoride varnish alone and silver diamine fluoride with sodium fluoride varnish groups than in the silver diamine fluoride alone group. There was no difference in the silver diamine fluoride with sodium fluoride varnish and sodium fluoride varnish alone groups for both salivary and plaque fluoride levels. Considering fluoride levels in plaque, the sodium fluoride varnish group had significantly higher levels at 5 and 60 minutes than the silver diamine fluoride group and the silver diamine fluoride with sodium fluoride varnish group was significantly higher at 30 and 60 minutes in comparison to silver diamine fluoride alone. At 60 minutes, the silver diamine fluoride and sodium fluoride varnish groups had returned to baseline; this was at 24 hours for the silver diamine fluoride with sodium fluoride varnish group for salivary fluoride. For plaque levels, the return to baseline was at 60 minutes for the silver diamine fluoride group, and 24 hours for the sodium fluoride varnish and silver diamine fluoride with sodium fluoride varnish groups. CONCLUSIONS: Children receiving sodium fluoride varnish and silver diamine fluoride had higher plaque and salivary fluoride levels than those treated with silver diamine fluoride alone in the short term. Plaque and salivary fluoride levels returned to baseline at 24 hours for all groups.