Objective: To compare the effect of surface treatment on the shear bond strength of ceramic and stainless steel orthodontic brackets to composite resin restorations.
Methods: Buccal surfaces of 90 premolar teeth were restored with a nano-hybrid composite resin. All the teeth were stored in de-ionized water for one week. Samples were divided into three groups of 30 according to different surface treatment (HF 5%, Airabrasion Al2O3 50μ and coarse diamond bur). Then each group was divided into 2 subgroups to be bonded to metal and ceramic brackets, with a no-mix adhesive resin. All the samples were thermocycled. Shear bond strength was determined with an Instron testing machine and the debonded interface was examined under stereomicroscope to assess the adhesive remnant index (ARI) on the restoration and bracket base.
Results: Student test showed significantly higher bond strength of ceramic brackets (23.09±7.19 MPa) than stainless steel brackets (15.56±5.13 MPa) (P<0.0001). ANOVA analysis showed significant differences among the conditioning groups with ceramic and stainless steel brackets. Both bracket types had significantly higher bond strength with diamond bur than HF (P<0.0001). ARI score showed mostly cohesive failure of the substrate with diamond bur, cohesive failure of the cement with air abrasion and adhesive failure of the cement- composite interface with HF.
Conclusion: The bond strength of orthodontic brackets to composite restorations might depend on bracket type and surface treatment for ceramic brackets because of higher bond strength, yet showing no destruction to the substrate composite restotration.