Fluoride varnish: it adheres to moist enamel, and that changes the protocol

Fluoride varnish is the form of professional fluoride application with the strongest evidence, and it has progressively replaced gels and foams for practical as well as efficacy reasons.

The usual concentration is five per cent sodium fluoride, corresponding to roughly 22,600 parts per million. That is an order of magnitude above any home product.

The decisive advantage over gel is adhesion. Varnish remains on the surface for hours, whereas gel is diluted by saliva within minutes of tray removal.

The prolonged contact time permits far greater fluoride release, and explains why varnish is more effective despite a briefer application.

The feature that surprises those used to gels is that varnish adheres better to moist enamel. Careful drying is unnecessary, and in some protocols moisture is actually favourable.

This makes it particularly suited to young children and poorly compliant patients, where achieving a dry field is difficult and maintaining it for four minutes impossible.

Application requires prior plaque removal, not necessarily a full hygiene appointment. Brushing or a pass with a prophylaxis cup suffices.

The quantity is minimal and should be respected: a few tens of milligrams for a full arch. Applying more does not increase efficacy and increases ingestion, which in young children is a relevant parameter.

Post-application instructions determine the result. The patient must not brush or eat hard foods for some hours, typically until the following day.

That period is when the varnish releases most of its fluoride, and brushing the same evening undoes much of the application.

Frequency should be calibrated to risk. Two applications a year is the reference for moderate risk; four are indicated in high risk, and the literature supports that intensification.

On primary teeth there is a further indication, particularly in early non-cavitated lesions, where varnish can arrest progression and avoid a restorative intervention in a young child.

In summary: it adheres to moist enamel and needs no drying, the quantity is minimal and should be respected, post-application instructions determine efficacy, and frequency follows risk with four annual applications in high-risk cases.