Variables of Experimental Primer that Affect Adhesion Strength to Zirconia

Methods: 5% water in ethanol mixture prepared and allowed to stabilize for 24 hours. Prepared solution then divided into two separate beakers. Acetic or hydrochloric acid was added to sample A and B respectively until pH of 4.5 obtained and stabilized. 5 samples were prepared of each solution A and B with different concentrations of APTMS. Volume percentages of APTMS in samples 1-5 are: 0%, 2%, 4%, 6%, and 8% respectively for both A and B. Fully sintered zirconia blocks (Comprodent, Izmir, Turkey) were rinsed in pure ethanol and well dried. Three drops of experimental primer were applied onto zirconia surface and left for 3 minutes then air-dried. Gelatin capsules containing pre-polymerized ARC (High-Q Bond ARC, B.J.M. Laboratories, Or-Yehuda, Israel) were attached to zirconia surfaces with fresh ARC followed by light curing for 20 seconds. Zirconia specimens (n=8) with each one of primer samples 1-5 of solutions A and B were prepared. Additional set of specimens was prepared with untreated zirconia and was used as a reference. All specimens were allowed to polymerize for 10 minutes, then were placed at 37⁰c thermostat in water for 24 hours. Shear bond strength measured using material testing machine (Lloyd instruments).

Results: shear bond strength for samples 1-5 for solution A are: 9.3±4.6MPa, 22.1±3.8MPa, 17.3±7.4MPa and 20.8±3.2MPa respectively. For solution B the results are: 5.4±3.9MPa, 11.6±3.3MPa, 9.1±3.1MPa, 6.5±2.8MPa and 4.5±2.1MPa respectively and for reference sample is 3.0±0.9MPa.

Conclusions: within limitations of this work, the experimental primer that contains 4% of APTMS and organic acid provides highest adhesion to zirconia surface.