Preparation of hard dental tissues by Er:YAG laser represents an alternative of classical mechanical preparation. In view of the mechanism of removing dental tissues (microexplosion) the given way of preparation is suitable especially for adhesive materials. When using energy around 100 mJ/cm2 a system of unevenness develops in enamel and dentin, which may be used for mechanical retention of composite materials.The author informsabout electron microscopic picture of enamel and dentin after irradiation by Er:YAG laser of the energy 105 mJ/cm2. The appearance of enamel resembles the situation after etching with orthophosphoric acid – the prismatic structure is evident,but the ends of enamel prismsare rounded.The surface of dentin is uneven with apparent entrances into the dentin tubules, which is narrower in comparison with dentin treated with orthophosphoric acid. The adhesive preparation of hard tooth tissues by laser radiation is well-founded especially in such cases, where the „laser etching“ fluently follows after preparation of cavity.

        Key words: laser etching – adhesive preparation