Methods: In this triple-blind randomized controlled clinical trial 46 children aged 2-15 who met the inclusion criteria entered the study and were divided into two age groups of 2-6 and 6-15 by Stratified Randomization. Participants were randomly allocated in the three following groups: Group 1 (Control): No varnish application, Group 2: Chlorhexidine varnish (Cervitec Plus, Ivoclar V), and Group 3: Fluoride varnish (Fluor Protector, Sultan Healthcare Inc, USA). In the first session, the baseline pH of inter-proximal dental plaque of all participants was measured by pH Plaque Indicator Kit (GC America, USA) and then the related varnishes were applied according to the manufacturer instructions in each group. The application of varnishes was done by dental floss into the proximal surfaces. After 1 and 3 months, the interproximal plaque pH was measured again. The data were analyzed by Kruskal wallis test and set to 0.05.
Results: Statistical analysis showed that once application of none of the varnishes could change the interproximal plaque pH significantly in different groups and different times (P>0.05).
Conclusions: Applying fluoride varnish or chlorhexidine varnish did not cause any changes in the interproximal pH plaque in different groups in comparison to the control group. Varnish application of more than once is recommended and needs further research.