Effects of Surface Pretreatments on Bond Strength and Morphology of Aprismatic Enamel

Purpose: To evaluate the effect of different pretreatment protocols and adhesives on the shear bond strength and surface morphology of aprismatic enamel.
Materials and Methods: Human maxillary incisors (N = 120) were assigned to five different groups according to pretreatment: 1) no treatment; 2) glycine; 3) sodium bicarbonate; 4) Al₂O₃ and 5) extra-fine bur. Then the teeth were divided into three subgroups, according to the adhesive applied: 3-step etch-and-rinse (ER), universal adhesive in ER mode, and universal adhesive in self-etch (SE) mode. Shear bond strength (SBS) testing was performed with a universal testing machine. For SEM observation, fifteen human molars were collected and analyzed after pretreatment with/without etching with 37% H₃PO₄ for 30s.
Results: Al₂O₃ showed higher SBS than all other groups considered. Comparable SBS values were obtained for other pretreatments. Universal adhesive in E&R mode performed better than did 3-step E&R and universal adhesive in SE mode. SEM images showed visible differences in enamel surface roughness.
Conclusions: Airborne-particle abrasion with Al₂O₃ followed by etching with H₃PO₄ increased SBS on aprismatic enamel. The combination of airborne-particle abrasion with alumina powder followed by 15 s of H₃PO₄ etching and application of a universal adhesive in E&R mode proved to be the most effective adhesive protocol.