Effect of self-etching primers on bond strength--are they reliable?

Currently introduced self-etching primers combine conditioning and priming agents into a single product. The purpose of this study was to determine the effects of using three self-etching primers on the shear bond strength (SBS) of orthodontic brackets and on the bracket/adhesive failure mode. Brackets were bonded to extracted human teeth according to one of four protocols. In the control group, teeth were etched with 37% phosphoric acid. In the experimental groups, the enamel was conditioned with three different self-etching primers, Clearfil SE Bond (CSE), Etch & Prime 3.0 (EP3), or Transbond Plus (TBP), as suggested by the manufacturer. The brackets were then bonded with Transbond XT in all groups. The present in vitro findings indicate that conditioning with TBP before bonding orthodontic brackets to the enamel surface resulted in a significantly (P < or = .001) higher SBS (mean, 16.0 +/- 4.5 MPa) than that found in CSE, EP3, and the control (acid-etched [AE]) groups. CSE produced bond strength values (mean 11.5 +/- 3.3 MPa) that are statistically comparable to those produced by acid etching (mean 13.1 +/- 3.1 MPa). The use of EP3 for enamel conditioning resulted in the lowest mean SBS value (mean 9.9 +/- 4.0 MPa). A comparison of the adhesive remnant index scores indicated that there was more residual adhesive remaining on the teeth that were treated with conventional acid etching than in the CSE and EP3 groups. In the TBP group, the failure sites were similar to those of the AE group but different from those of the CSE group.