Fluoride varnish is a concentrated topical fluoride containing sodium fluoride in a resin or synthetic base. The application of fluoride varnish has been proven an effective method of reducing early childhood cavities by protecting teeth, re-mineralizing tooth outer layer and stopping the progression of initial cavities. It is usually applied in a thin layer with small brushes or cotton pellets at the frequency of two to four times a year. Varnish, when brushed onto the teeth, provides a highly concentrated dose of fluoride and maintains prolonged contact with outer layer to stop cavities. They are considered safe, even their high fluoride concentration, because the amount of varnish usually applied to treat one child is only 0.5 ml on average. It strengthens the teeth and protects them from cavities. It can be safely applied to children as early as the appearance of the first tooth in mouth and it can safely apply on adult also. Varnishes usually disappears over the following months and needs repeated applications to maintain effectiveness as a primary prevention strategy.