Debonding characteristics of self-adhesive resin cements used for orthodontic bonding relative to curing initiation time

Objective: The purpose of this study was to test whether the changing of the curing time initiation for two self-adhesive resin cements, Breeze (Pentron Clinical Technologies, Wallingford, USA) and Smartcem2 (Dentsply Caulk, International Milford, USA) can be used successfully to bond orthodontic brackets. Methods: Sixty extracted premolars were used in this study. The teeth were divided into 4 groups according to the cement used and its mode of curing. Breeze and Smartcem2were cured immediately and after 60 seconds after bracket placement. The brackets were tested in shear using a universal testing machine then the enamel surface was examined under 40x magnification to determine the amount of adhesive remnant. Six premolars from each group were then sectioned buccolingually into two halves. One half was chosen and gold coated to be examined under scanning electron microscope. Results: Analysis of variance for shear bond strength showed no significant differences among all the groups where the SBS ranged from 4.29 to 5.30 MPa. It was found that in both types of self adhesive resin cements most of the failure occurred at the bracket tooth interface. Scanning electron microscope showed deeper resin penetration for Breeze and Smartcem2 cured after 60 seconds with  a mean resin depth ranged from 3.25 :m to 4.51 :m respectively. No resin tags were observed in groups immediately cured. Conclusions: The SBS values of brackets cemented with self-adhesive resin cements were below the optimum levels for use in orthodontic bonding and the formation of short resin tags with delayed curing did not increase the shear bond strength of self-adhesive resin cements.