Laser Er:YAG et odontologie restauratrice

Abstract

The capacity of Er:YAG laser (λ = 2,940 nm) both to eliminate carious tissues and to prepare cavities for adhesive restorations has been widely demonstrated. The marketed apparatus allow cavities preparation with a suitable clinical working time. All of them are equipped with an internal cooling system for air and water pulverisation at the impact point of the laser beam. This system limits intrapulpal temperature rise to less than the biologically acceptable threshold of 5°C. Histological studies showed that the pulpal response to the Er:YAG laser irradiation of dental hard tissues is minor, localised and reversible, equivalent to those consecutive to the use of high speed rotative instruments in the same refreshment conditions. When Er:YAG laser has been used on dentin, the microscopic examinations revealed the absence of smear layer and open dentinal tubules. The intertubular dentin is partially removed due to the larger water content in its composition. Conversely, Er:YAG laser is less effective on peritubular dentin; it does not enlarge the tubule orifices, providing a microcrater-like appearance of laser irradiated surfaces. Direct composite resin bonding to the Er:YAG laser irradiated dentin, without acid pre-treatment, has been suggested. In a recent publication, the authors demonstrate that acid pre-treatment of the irradiated dentin surface results in similar microscopic observations at dentin-composite resin interfaces when compared with dentin bur preparation. The adhesion values of the composite resin to the irradiated dentin with or without acid etching are comparable to those measured with conventional bonding (bur + acid). Conversely, composite restorations of laser Er:YAG cavity preparations show significantly less microleakage when orthophosphoric acid is applied before bonding. First clinical applications concerning the preparation of Er:YAG laser cavities did not show any side effects. The absence of pain, noise and vibrations are of value in comparison with conventional mechanical preparations.