Objectives: To determine direct effect of irradiation to enamel and to test the effect of fluoride varnish application to the enamel surface before and after irradiation .
Methods: Laboratory experiments were used with observation of pre and post controlled random sampling. Preliminary studies were applied to determine the irradiation effect to calcium ion loss and surface hardness. Then, the test was done to determine the suitable time to apply the fluoride varnish before irradiation. Enamels of 180 premolars were used to determine the calcium ion loss. For hardness test, the specimens used were 60 enamels. All samples were kept in artificial saliva.
Result: There was an increase of calcium ion loss and a decrease of surface hardness after irradiation. Fluoride varnish application reduced the ion calcium loss and reduced hardness.
Conclusion: Direct irradiation changed the enamel structure as observed in calcium ion loss and the surface hardness. Application of fluoride varnish reduced the change of enamel structure after irradiation. Artificial saliva during irradiation changed the structure of enamel but did not interfere with the effectiveness of fluoride varnish. Furthermore, the artificial saliva could preserve the enamel hardness.
Key words: enamel, irradiation, calcium ion loss, enamel surface hardness and fluoride varnish.