The effectiveness of the biannual application of silver nitrate solution followed by sodium fluoride varnish in arresting early childhood caries in preschool children: study protocol for a randomised controlled trial

BACKGROUND: The application of 38 % silver diamine fluoride (SDF) has been shown to be effective in arresting early childhood caries (ECC). Since SDF is not available in certain countries, some dentists use adjunctive application of 25 % silver nitrate (AgNO(3)) and 5 % sodium fluoride (NaF) to arrest ECC. This randomised controlled trial will systematically compare the efficacy of a 25 % AgNO(3) solution followed by 5 % NaF varnish with that of a 38 % SDF solution in arresting ECC when applied at half-yearly intervals over a 30-month period. METHODS/DESIGN: This study is a randomised, double-blinded, non-inferiority clinical trial. The hypothesis tested is that adjunctive application of 25 % AgNO(3) followed by 5 % NaF is at least not appreciably worse than a 38 % SDF in arresting ECC. Approximately 3100 kindergarten children aged 3–4 years will be screened and at least 1070 children with caries will be recruited. This sample size is sufficient for an appropriate statistical analysis (power at 90 % (β = 0.10) with a 2-sided type-I error of α = 0.05), allowing for an overall 20 % drop-out rate. The children will be randomly allocated into 2 groups to treat their caries over a 30-month period: Group A – biannual adjunctive application of a 25 % AgNO(3) solution and a 5 % NaF varnish, and Group B – biannual adjunctive application of a 38 % SDF solution followed by a placebo varnish. Clinical examinations will be conducted at 6-month intervals. Primary outcome measured is the number of active caries surfaces which are arrested. Information on confounding factors such as oral hygiene habits will be collected through a parental questionnaire. DISCUSSION: We expect that adjunctive application of 25 % AgNO(3) solution and 5 % NaF varnish and of 38 % SDF solution can both effectively arrest ECC. Lower concentrations of silver and fluoride are contained in 25 % AgNO(3) and 5 % NaF, respectively, than in 38 % SDF; therefore, AgNO(3)/NaF are more favourable for use in young children. Because its use for caries management is painless, simple, low-cost, and approved in many countries, AgNO(3)/NaF could be widely recommended and promoted as an alternative treatment to conventional invasive management of ECC. TRIAL REGISTRATION: ClinicalTrials.gov: NCT02019160. Date of registration: 11 December 2013. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13063-015-0960-2) contains supplementary material, which is available to authorized users.