SEM analysis of dentin treated with the Er:YAG laser: a pilot study of the consequences resulting from laser use on adhesion mechanisms

• Objectives: the purpose of this study was to compare morphological characteristics of lased dentinal surfaces produced by chemical etching before or after laser treatment and to evaluate the adhesive interface after application of an adhesive–composite system. • Methods: eighteen permanent molars, caries free, have been transversally cut to obtain dentinal surfaces. Ten of these surfaces have been divided into three main groups according to preparation modality: only laser, laser followed by chemical etching, chemical etching before laser. Er:YAG laser has been used with two different energy output: 200 mJ and 400 mJ at 1Hz. The other eight surfaces, divided into two groups, have been prepared following the same modalities of the other groups, but using 4Hz of frequency. An adhesive system (Scotchbond 1, 3M), a thin layer of flowable composite (Tetric Flow, Vivadent) and a regular composite (Z250, 3M) have been applied on every dentinal surface and separately light cured. In order to evaluate dentine-restoration interface, the samples have been longitudinally cut and prepared for SEM observation. • Results: dentinal surfaces, etched by laser treatment, don’t show the suitable characteristics to guarantee a good bond with adhesive materials. Observation of dentine-restoration interface shows micro fractures just under the lased dentinal surface. • Conclusions: at the moment, it is questionable whether to use Er:YAG laser as an alternative to conventional techniques of acid etching. Given that the actual adhesive systems necessarily require acid conditioning, it wouldn’t be advisable to skip this operative step.