Use of phosphoric acid etchants with Scotchbond Multi-Purpose

An earlier study showed that Scotchbond Multi-Purpose, which uses a 10% maleic acid dentin/enamel etchant, had lower enamel bond strengths than those typically obtained by etching with 35-40% phosphoric acid. Therefore, the possibility of substituting phosphoric acid for maleic acid in the Scotchbond system might be considered. The purpose of this study was to evaluate the dentin bond strengths of Scotchbond Multi-Purpose when various phosphoric acid agents were used to etch the dentin. Proximal dentin surfaces of extracted human molars were etched with 10% maleic acid, 35% phosphoric acid, 32% phosphoric acid, 10% phosphoric acid or 25% phosphoric acid with aluminum oxalate (Etch 'N' Seal). Scotchbond Multi-Purpose Primer and Adhesive were applied as directed and composite posts were bonded to the dentin. After thermocycling, the composite was fractured off using an Instron testing machine. Mean dentin bond strengths were 17.3 MPa for 10% maleic acid, 17.2 MPa for 10% phosphoric acid, 15.2 MPa for 35% phosphoric acid, 13.6 MPa for 32% phosphoric acid, and 5.2 MPa for Etch 'N' Seal. The bond strengths for all groups except Etch 'N' Seal were statistically similar.