SEM ANALYSIS OF DENTIN TREATED WITH ER:YAG LASER: A PILOT STUDY OF CONSEQUENCES RESULTING FROM LASER USE ON ADHESION MECHANISM

The purpose of this study was to compare the morphological characteristics of lased dentinal sur-faces obtained by chemical etching, which was applied either before or after laser treatment. The adhesive in-terface after the application of an adhesive– composite system on the above mentioned dentinal surfaces wasalso evaluated. Materials and Methods:Eighteen caries-free permanent molars were transversally cut to obtainthe dentinal surfaces. T en of these surfaces were divided into three main groups according to their preparationmodality: laser only, laser followed by chemical etching, and chemical etching before laser. The Er:YAG laserwas used with two different energy outputs: 200 and 400 mJ at 1 Hz. The eight remaining surfaces were dividedinto two groups and followed the same preparation as the first three groups. The only difference was a changein frequency: 4 Hz was used for treating these surfaces. An adhesive system (Scotchbond 1, 3M), a thin layer offlowable composite (T etric Flow, Vivadent), and a regular composite (Z250, 3M) were applied to each dentinalsurface and then separately light cured. In order to evaluate the dentine– restoration interface, the sampleswere cut longitudinally and prepared for SEM observation. Results: The dentinal surfaces that were etched bythe laser treatment did not demonstrate the characteristics necessary for guaranteeing a good bond with theadhesive materials. A closer observation of the dentine– restoration interface revealed some micro-fractures lo-cated just below the lased dentinal surface. Conclusion: The decision to use the Er:YAG laser as an alternativeto conventional techniques of acid etching is currently arguable. Given that the available adhesive systems re-quire acid conditioning, it would not be advisable to skip this operative step