Fluoride remains the foundation of caries prevention, but high fluoride concentration alone does not guarantee optimal remineralisation. Fluoride activity is influenced by formulation, retention time, saliva quality, pH, calcium and phosphate availability, and the ability of ions to remain bioavailable long enough to affect the lesion environment.

This presentation reframes fluoride varnish therapy through the lens of modern caries science: a dynamic, biofilm-mediated process governed by repeated cycles of demineralisation and remineralisation. It will explore how fluoride acts at the tooth surface, why calcium and phosphate availability are critical, and how different high-fluoride delivery systems including APF gels, first-generation sodium fluoride varnishes, and varnishes containing fTCP and RECALDENT™ (CPP-ACP) differ in release kinetics, ion behaviour, and clinical intent.

Particular focus will be given to the distinction between surface-dominant fluoride effects, such as calcium fluoride-like reservoir formation, and the conditions that support deeper mineral recovery within early subsurface lesions. The presentation will also examine how RECALDENT™ (CPP-ACP) helps to maintain calcium and phosphate in a bioavailable form to support fluoride-mediated remineralisation.

The aim is to translate these mechanisms into practical clinical decision-making: selecting the most appropriate fluoride strategy based on caries risk, salivary status, lesion activity, and treatment goals.