Effect of different surface treatments and bonding modalities on the shear bond strength between metallic orthodontic brackets and glazed monolithic zirconia crowns.

OBJECTIVE

To evaluate the effect of different surface treatments and bonding modalities on the shear bond strength (SBS) between metallic orthodontic brackets and zirconia crowns.

MATERIALS AND METHODS

Sixty zirconia specimens were computer-aided design/computer-aided manufacturing milled, sintered, glazed, and embedded in acrylic resin. The specimens were divided into three groups according to the surface treatment applied: C: no surface treatment (control), S: sandblasted with 50 μm AlO, and D: Sof-Lex disc roughening. Each group was further subdivided into two subgroups according to the resin cement used: P: Clearfil Ceramic Primer + Panavia F2.0 (Kuraray) and R: RelyX U200 (3M/ESPE). Metallic orthodontic brackets were bonded to the labial surface of the specimens. All specimens underwent thermocycling. SBS test was applied using a universal test machine at a cross head speed of 1 mm/min. Data were analyzed using Mann-Whitney test (α = 0.05).

RESULTS

Subgroup SP showed the highest SBS (20.8 ± 4.8 MPa), followed by subgroups SR (16.7 ± 4.6 MPa), DP (12.3 ± 2.8 MPa), and DR (11.6 ± 3 MPa). However, all specimens in the control group underwent debonding during thermocycling. The different surface treatment groups showed highly significant differences ( < 0.05), whereas the resin cement subgroups showed no significant differences ( > 0.05).

CONCLUSION

SBS between glazed zirconia crowns and metallic brackets strongly depended on the surface treatment applied. Sandblasting achieved the highest SBS. Roughening with Sof-Lex disc proved to be a reliable surface treatment modality for glazed zirconia. Bonding to untreated glazed zirconia surfaces led to bond failure. Both resin cements yielded strong SBS results.