Thesis & Dissertations

Statement of problem: Successful orthodontic treatment requires a tight bond between the crown/tooth and orthodontic brackets. Despite all the advantages of full monolithic zirconia crowns, achieving a good bond to zirconia is still a challenge. Purpose: This study evaluated the shear bond strength (SBS) between zirconia crowns and metallic brackets using different surface treatments and two different resin cements. Material and Methods: Full anatomical zirconia crowns were milled, sintered, glazed and embedded in acrylic resin. The crowns were divided into three groups according to the surface treatment applied: C=control (no surface treatment), S= Sandblasted with 50μ Al2O3, D= Sof-lex Disc. Each group was further subdivided into two subgroups with respect to the resin cement used (P= Panavia F2.0 and R= RelyX U200). Metallic orthodontic brackets (Discovery, Dentaurum) were bonded to the labial surface of each specimen. All the specimens underwent thermo-cycling. SBS test was applied using universal test machine at cross head speed of 1 mm/min. Data were analyzed using Mann-Whitney test (α =.05). Results: The SP subgroup showed the highest SBS (20.8 ± 4.8MPa), followed by the SR subgroup (16.7± 4.6 MPa). The DP (12.3 ± 2.8MPa) and DR (11.6 ± 3 MPa) subgroups showed lower SBS values. While both control subgroups CP and CR debonded during thermo-cycling and received zero value. The statistical analysis between the resin cement subgroups revealed no statistical significance with (p=.547). Conclusion: Both cements tested obtained strong SBS results. The SBS between monolithic zirconia crowns and metallic brackets is strongly dependent on the surface treatment applied. Sandblasting showed the highest SBS among the surface treatments. Roughening with Soflex disc proved to be an alternative way when sandblasting is not available. Bonding to untreated glazed zirconia surface eventually leads to bond failure. Keywords: zirconia, bracket, shear bond strength, air abrasion, Sof-lex disc, resin cement.