A systems approach using the functional resonance analysis method to support fluoride varnish application for children attending general dental practice

•Fluoride varnish is safe and effective for caries prevention.•Varnish application takes place in a complex organisational system.•Intervening in healthcare requires system level theorizing and modelling.•The Functional Resonance Analysis Method allows for accessible systems models.•Intervention that takes into account system variability is more likely to succeed.