Effect of Phosphoric Acid Etching on Tensile Bond Strength of Universal Adhesive to Repair Ceramic Restoration

Objectives: In this study, we investigated that the effect of phosphate etching on tensile bond strength of universal adhesive to repair ceramic restoration.
Methods: Ceramic block for CAD/CAM (GN Ceram Block, GC) and four types of universal adhesives (Scotchbond Universal Adhesive, All-Bond Universal, Beauti Bond Multi and Universal Primer) were used in this study. Surfaces of ceramic blocks were grinded with SiC paper, grit #600, were etched with 30% phosphoric acid, PA, for 15sec. Each universal adhesive was applied on the surface according the manufacturer instructions. Then cylindrical stainless mold (3.0mm height, 4.0mm diameter) was put on the surface and resin composite was filled. Those specimens were stored in distilled water at 37℃. After 24hrs, tensile bond strength, TBS, was measured by universal testing machine (cross head speed at 0.5mm/min). The data were statically analyzed by Two-way ANOVA at P<0.05.
Results: In Scotchbond Universal Adhesive, TBS with/without PA were 17.3±4.7MPa/13.7±2.6 MPa. In All-Bond Universal, TBS with/without PA were 16.0±3.0MPa/16.6±3.8MPa. In Beauti Bond Multi, TBS with/without PA were 10.5±2.2MPa/16.9±2.5MPa. In Universal Primer, TBS with/without PA were 14.8±2.2MPa/16.3±2.1MPa. Statistically, there were interaction between etching with PA and types of adhesive in Two-way ANOVA.
Conclusions: The results in this study suggested that etching with phosphoric acid might alter the bond strengths when the case of repair for ceramic by universal adhesive.