The success of resin composite restorations is reliant upon adhesion to the underlying tooth via adhesive systems. The mechanism of adhesion to enamel and dentine could be involved for one hand, the etching the substrates with 30-40% phosphoric acid, followed by the application of a primer and subsequently an adhesive resin 3 steps etch-and- rinse approach or 2 steps when to combine the primer and adhesive into one bottle. For another hand, the self- etch systems with acid monomers in their primer, allow conditioning the surface without phosphoric acid step. So, they consist of either a self-etching primer accompanied by an adhesive resin applied as a subsequent step (2 steps) or a self-etch adhesive, which does not require a separate primer (1 step).