Effects of etchants and primers on shear bond strength of a self-ligating esthetic orthodontic bracket

Introduction: Damon 3 orthodontic brackets (Ormco, Orange, Calif), combining a self-ligating bracket with a composite bracket pad were the subject of an in-vitro bonding study to determine the shear bond strength to enamel and adhesive remaining on the teeth with various enamel and bracket preparation procedures. Methods: A 3 × 2 factorial design was selected with the following factors as variations of the enamel preparation: liquid phosphoric acid etchant followed by primer (Ortho Solo; Ormco), gel phosphoric acid etchant followed by primer, and self-etching primer (Transbond Plus; 3M Unitek, Monrovia, Calif). The second factor was a primer (Ortho Solo) either applied to the bracket pad or absent as a control. Results: No statistically significant differences were observed in shear bond strengths, with group average estimates ranging from 14.5 to 16.6 MPa. Debonding predominantly occurred at the bracket-pad interface with no significant differences in adhesive remaining on the teeth. Conclusions: This in-vitro study indicated that self-etching primer, gel etchant, and liquid etchant produce equal and sufficient bond strengths. Furthermore, application of primer to the bracket pad does not improve bond strength.