Introduction: This study was conducted to compare the effects of 6 self-etching primers (SEPs) on the shear bond strength (SBS) of orthodontic brackets bonded with the same orthodontic composite resin. Methods: One hundred forty extracted premolars were randomly divided into 7 groups (20 per group). In group I (control), the enamel was etched with 37% phosphoric acid. In the other groups, it was conditioned with SEPs according to each manufacturer's instructions: group II, Transbond Plus SEP (3M Unitek, Monrovia, Calif); group III, AdheSE (Ivoclar Vivadent AG, Schaan, Liechtenstein); group IV, Primers A and B (Shofu, Kyoto, Japan); group V, Clearfil Mega Bond FA (Kuraray Medical, Tokyo, Japan); group VI, Peak SE and Peak LC Bond (Ultradent Products, South Jordan, Utah); and group VII, Bond Force (Tokuyama, Osaka, Japan). All brackets were bonded with Transbond XT (3M Unitek), and the teeth were then stored (37 degrees C, 24 hours), tested, and statistically analyzed (Scheffe, ANOVA [ P < 0.05], and Weibull analyses). The adhesive remnant index (ARI) was also recorded. Results: Group I (26.5 +/- 8.1 MPa) had a significantly higher SBS value than the other groups except group II (21.1 +/- 6 6.2 MPa). There were no significant differences among groups II, V (19.0 +/- 4.3 MPa), VI (19.6 +/- 5.1 MPa), and VII (18.3 +/- 4.4 MPa). The values for groups I, II, and VI were significantly higher than for group III (13.4 +/- 4.1 MPa), and the value for group IV (8.8 +/- 2.6 MPa) was significantly lower than the values for groups I, II, V, VI, and VII. Significant differences were found in the ARI scores. Conclusions: The SBS values of all groups might be clinically acceptable, and orthodontic brackets can be successfully bonded with Transbond XT after enamel conditioning with any of these SEPs. However, since the SEPs used in groups III and IV significantly affected the bond strength negatively, further studies are warranted to evaluate their effectiveness. (Am J Orthod Dentofacial Orthop 2009; 135: 424.e1-424.e7)
