Fluoride is proven caries preventive and therapeutic agent. It helps in the remineralization of early enamel caries lesions and subsequently increases its resistance to dissolution by acids produced by cariogenic microflora. Topical fluoride varnish was introduced in the 1960s. The Food and Drug Administration (FDA) in the USA approved the use of fluoride varnishes for dentistry in 1994 and presently fluoride varnish is the most commonly used professionally applied topical fluoride agent. The most popular topical fluoride varnish is Duraphat®, which contains 5% NaF varnish (2.2% Fluoride). The greatest advantage of topical fluoride varnish is its ability to adhere to tooth tissues for a longer period of time that enables improved fluoride uptake. It allows the continuous release of fluoride ions into enamel, dentine, plaque, and saliva. Additionally, the application of topical fluoride varnish is a simple procedure and does not require great patient co-operation. Topical fluoride varnish application has been reported to exhibit substantial caries inhibiting effect in both permanent and primary teeth.

Among the various forms of fluoride products, such as gels, varnishes, foams, mouth- rinses, and toothpastes, varnishes do not rely on patient compliance and cooperation. The major advantage of varnishes is high retention followed by gradual release of fluoride over an extended time period, which leads to low concentrations in the liquid plaque-enamel interface. The use of fluoride diminishes demineralization and promotes remineralization, thereby balancing the process of caries formation. A recent Cochrane review has revealed moderate evidence for the prevention of EWSLs during fixed orthodontic treatment by fluoride varnish application every six weeks at the time of orthodontic review, but this finding is based on a single study. Therefore, the quality of the evidence found is moderate and the review recommendations state that additional well- conducted research is required in this area.

Caries preventive and inhibiting effect of topical fluoride therapy depends on an adequate supply of calcium and phosphate ions. Though calcium and phosphate ions are supplied naturally by saliva, the concentration of such ions is low (even lower in patients suffering from reduced salivary flow). Low concentration of salivary calcium and phosphate ions leads to a mineral deposition only at the surface of the enamel as a result of a low ion concentration gradient. The deposition of minerals at the surface of enamel alone may not improve the structural properties of the deeper part of the early-stage or incipient caries lesions. This has led to the introduction of calcium phosphate-based delivery systems containing high concentrations of calcium phosphate such as tri-calcium phosphate (TCP).

Tri-calcium phosphate (TCP) is a product resulting from ball milling beta-tri-calcium phosphate with sodium lauryl sulphate. ClinproTM white varnish (3M ESPE, St Paul, MN, USA), which contains TCP and NaF, is a commercially available topical fluoride varnish, which claims that the protective fumaric acid barrier facilitates co-existence of calcium and fluoride ions, however, during storage, the unwanted reaction between the ions is prevented. The protective barrier breaks upon contact with saliva, releasing the ions for effective remineralization of the tooth. At present there is no clinical study to prove the superior EWSLs-preventive effect of this newer NaF varnish with TCP when compared to conventional topical NaF varnish in patients undergoing fixed orthodontic treatment.