Effect of Primer before Resin Cement on Bracket Base and the Influence of Storage Time on Shear Bond Strength

Abstract

Background: The elapsed time after bracket bonding and sandblasting the base could influence the shear bond strength (SBS) to enamel. Aim: This study evaluated the effect of primer application on the bracket base before application of resin and its interaction with storage time and sandblasting factors on SBS. Materials and Methods: Brackets were bonded on the enamel surface of 160 bovine incisors divided into eight groups (n = 20) with mesh bases, with and without sandblasting, with different storage times (immediately and 24 h), and with two different techniques (with and without primer on the base before resin). Results: SBS mean in conventional and primer groups ranged from 23 ± 7.76 MPa to 48 ± 11.34 MPa, respectively. After 24 h period, SBS increased when the primer was applied before resin on the bracket bases (P < 0.001). The effect of each isolated factor (storage time and primer application) was statistically significant (P < 0.001). Primer application versus time factors was statistically significant (P < 0.001). Sandblasted bases were not influential on SBS separately or by any of the interaction factors (P = 0.628). Adhesive interface failures were significant when the adhesive remnant index was evaluated regarding storage time without primer (P = 0.022); however, primer application did not show significance when the time was evaluated (P = 0.686). Conclusion: Primer increases the SBS after a 24 h period. Most of the failures occurred at the enamel/adhesive interface. Sandblasting treatment of bracket bases did not influence the SBS.