Shear bond strength of orthodontic brackets with self-adhesive resin cements

Purpose: this investigation determined shear bond strength (SBS) of metallic and ceramic orthodontic brackets with new self-adhesive cements. Methods: 100 extracted caries-free premolars were employed. These were sterilized with Gamma irradiation and their roots embedded in stone bases maintaining facial surfaces perpendicular to bottom of the bases. Teeth were pumiced with course pumice and rubber cups for 10 seconds and then rinsed and dried. Teeth were randomly divided into two main groups according to metallic or ceramic brackets (Victory series 3M Unitek). In each group, specimens were further divided into five subgroups according to cement used: Transbond XT LC, 3M Unitek (TBXT) (etch-and-rinse control), Esthetic Cementing System, Kuraray (ECS) (self-etch), Rely-X Unicem, 3M ESPE (RXU) self-adhesive, Biscem DC, Bisco (BSCM) self-adhesive, Breez, Penetron (BRZ) self-adhesive. Ten brackets were cemented in each subgroup (n=10). Specimens were stored in distilled water at 37 oC for 7 days and subjected to 3,000 thermocycles between 5 and 55 oC. Brackets were then debonded in shear using Instron. Results: Means and standard deviations in MPa for metal brackets were: 18.6 (4.9), 6 (1.7), 6 (1.5), 2.2 (1.0) and 8.4 (3.1) for TBXT, ECS, RXU, BSCM and BRZ, respectively. For ceramic brackets values were: 22.7 (5.0), 17 (5.3), 7.7 (2.5), 1.6 (0.4) and 9.5 (4.9) for TBXT, ECS, RXU, BSCM and BRZ, respectively. ANOVA revealed significant differences among the subgroups(p<.05)for both brackets types. For ceramic brackets Tukey's revealed no statistical difference in mean SBS between TBXT and ECS. Conclusion: SBS of orthodontic brackets cemented with traditional etch-and-rinse cement was significantly higher than when all three self-adhesive cements were used. However, when the self-etch adhesive (ECS) was used with ceramic brackets no significant difference was found in SBS as compared to TBXT(P=.052).

Acknowledgment: Materials received from 3M/Unitek, Kuraray, 3M/ESPE, Penetron and Bisco.