Bond Strengths of Orthodontic Self-etching Primers to Unground Enamel

Objectives: To compare in vitro bond strengths to unground human enamel among several orthodontic self-etching primers to traditional orthodontic bonding with Transbond with 37% phosphoric acid as a control. Methods: Sixteen non-carious third molars were sectioned in a mesio-distal direction. The buccal or lingual enamel segments were imbedded in acrylic and placed in water bath for 24 hours at 37 C. The teeth were then pumiced and air-dried for 5 seconds and divided into 4 groups of 8 specimens and bonded according to manufacturers' directions. Ideal 1 (I1, GAC), First Step (FS, Reliance), Transbond Plus (TP, 3M Unitek) and Transbond with 37% phosphoric acid (TPA, 3M Unitek) were used to bond a cone of the manufacturer's recommended orthodontic resin cement with a diameter of 3 mm on the enamel surface. The teeth were then incubated in the water bath for 24 hours at 37 C. Debonding was performed (Instron 4465) at a crosshead speed of 0.5 mm/min. Adhesive Remanent Index (ARI) was determined by optical microscopy. Data were analyzed by analysis of variance. Results: Tensile bond strengths (MPa, n=8) were: I1, 8.8 (3.2); FS, 20.5 (8.8); TP, 18.3(7.7); and TPA, 34.8 (11.2). The ARI (%) results were: I1, A65/ C35; FS, A39/C54/T7; TP, A66/C21/T13; and TPA, A91/C 9. Analysis of variance showed no significant difference between the bond strengths of the self-etching primers FP and TP. Conclusion: All 3 self-etching primers had bond strengths greater than 8 MPa. Products were supplied by the manufacturers.