The caries-arresting effect of incorporating functionalized tricalcium phosphate into fluoride varnish applied following application of silver nitrate solution in preschool children: study protocol for a randomized, double-blind clinical trial.

Background: Dental caries in primary teeth is prevalent, affecting millions of children around the world. Functionalized tricalcium phosphate (fTCP) has been incorporated into sodium fluoride (NaF) varnish to enhance the remineralization process. NaF varnish with the adjunctive application of silver nitrate (AgNO) solution is effective in arresting dentine caries. So far, there is no published randomized clinical trial investigating the effectiveness of the adoption of AgNO solution and NaF varnish containing fTCP in arresting dentine caries in preschool children. The objective of this study is to compare the effectiveness of a 25% AgNO solution plus a 5% NaF varnish containing fTCP and a 25% AgNO solution plus a 5% NaF varnish in arresting coronal dentine caries among preschool children when applied semi-annually over a 30-month period.

Methods/design: This is a randomized, double-blind controlled trial. The null hypothesis tested is that no difference exists between the effectiveness of a 25% AgNO solution plus a 5% NaF varnish with fTCP and a 25% AgNO solution plus a 5% NaF varnish in arresting dentine caries in preschool children when applied semi-annually. According to the sample size calculation, approximately 2000 3- to 4-year-old kindergarten children will be screened, and at least 408 children with coronal dentine caries will be recruited. The children will be randomly allocated to two treatment groups via stratified randomization: group A - biannual application of a 25% AgNO solution followed by a 5% NaF varnish, and group B - biannual application of a 25% AgNO solution followed by a 5% NaF varnish with fTCP. Clinical examinations will be conducted every 6 months to assess whether the carious lesions have become arrested (primary outcome). Confounding factors, such as demographic background and oral hygiene behaviors, will be collected through a parental questionnaire.

Discussion: The effectiveness of the topical application of a 25% AgNO solution followed by a 5% NaF varnish with fTCP in arresting coronal dentine caries among preschool children remains unknown. Because the proposed caries-arresting methods are simple, noninvasive and low cost, these can be widely recommended for caries control in young children.

Trial Registration: ClinicalTrials.gov (U.S.): NCT03423797 on 6 February 2018.