The effectiveness of fluoride interventions in reducing social inequalities in dental caries: a systematic review

This review systematically examines evidence on the effectiveness of fluoride interventions in reducing social inequalities in dental caries across population subgroups. The search for studies was conducted across four databases: PubMed, Web of Science, MEDLINE, and Scopus. We included observational and interventional studies that assessed the effectiveness of fluoride interventions in reducing social inequalities in dental caries. Studies focusing on institutional populations or examining combined fluoride interventions with other interventions were excluded. The quality of included studies was assessed using the Risk of Bias in Non-randomised Studies – of Exposure (ROBINS-E) tool, and the certainty of evidence was assessed using an adapted GRADE approach. Due to significant heterogeneity, a meta-analysis was not feasible. Twenty-eight studies were included, of which 26 examined community water fluoridation (CWF), one fluoride toothpaste, and one fluoride mouth rinse. Evidence was predominantly from children and adolescents, with no studies examining adults or the older population. Some studies reported narrower social inequalities in dental caries in the presence of CWF, particularly for absolute inequality measures, although findings were inconsistent across relative inequality measures and effect-modification analyses. Twenty-seven studies were rated as high or very high risk of bias, and one as moderate risk. Certainty of evidence was very low for CWF among children and adolescents, topical fluoride interventions, and evidence from low- and middle-income country settings. Evidence on the effectiveness of fluoride interventions in reducing social inequalities in dental caries remains uncertain. Findings suggested that CWF may contribute to narrower inequalities among children and adolescents, but the certainty of evidence was very low. High-quality research is needed to establish the causal relationship and magnitude of effect across different populations and settings. This systematic review was not registered.