Impact of fluoride varnish and oral health education on caries increment and dental plaque microbiota among children with early mixed dentition: a three-armed 24-month randomized controlled trial

ABSTRACT Dental caries is the most prevalent oral disease globally. A 24-month randomized controlled trial was conducted among 236 children aged between 7 and 8 years (ChiCTR2400084030). They were randomly allocated into three groups and received the following biannual interventions: Group 1: topical fluoride varnish (TFV) using 5% sodium fluoride; Group 2: oral health education (OHE); and Group 3: TFV + OHE. The interventions lasted for 12 months, and a final examination was conducted after 24 months to assess whether the desired effects sustained after the cessation of interventions. After 12-month interventions, when demographic and socioeconomic factors were adjusted, children in Group 1 were more likely to have new caries on their permanent first molars when compared to Group 2 (odds ratio [OR] = 2.86, 95% confidence interval [CI] 1.33, 6.14) or Group 3 (OR = 2.28, 95% CI 1.09, 4.78). There was no significant difference in Shannon diversity index across the three groups. Among the top 10 most abundant genera, Capnocytophaga , Saccaribactetia_(TM7)_[G-1] , Selenomonas , and Porphyromonas differed across the three groups after interventions. The 12-month assessment revealed a lower abundance of Capnocytophaga granulosa among children who did not receive TFV. Although the interventions might have the potential to alter the composition of supragingival dental plaque, the specific mechanisms and clinical significance require further investigation. IMPORTANCE Early mixed dentition is a critical transition period for children. During this phase, newly erupted permanent first molars (PFMs) with deep fissures are vulnerable to tooth decay. Considering increased independence in diet choices and inconsistent toothbrushing practices among these children, structured oral health education (OHE) is recommended to safeguard their oral health status. The main findings of this 24-month randomized controlled trial revealed that fluoride varnish alone is insufficient to prevent caries on PFMs, underscoring the necessity of reinforcing OHE for this age group. Additionally, dynamic shifts in supragingival plaque composition were observed, including Capnocytophaga , Saccaribactetia_(TM7)_[G-1] , Selenomonas , and Porphyromonas . Notably, Capnocytophaga granulosa , a species previously found among adults with periodontal diseases, was less abundant in children who did not receive fluoride varnish. While these findings highlight the impact of oral health promotion activities on alterations of oral microbiota, further research is needed to clarify the clinical implications of these microbial changes. CLINICAL TRIALS The study was registered with the Chinese Clinical Trial Registry ( ChiCTR2400084030 ).