Effect of etching with potassium hydrogen difluoride and ammonium hydrogen difluoride on bonding of a tri-n-butylborane initiated resin to zirconia.

The purpose of the current study was to evaluate the effect of etching with potassium hydrogen difluoride (KHF2) and ammonium hydrogen difluoride (NH4HF2) on the bond strength of a self-polymerizing methyl methacrylate resin (MMA-TBB) bonded to zirconia. Zirconia disks were prepared using the following surface treatment: no treatment, alumina blasting, and etching with KHF2 or NH4HF2. The specimens were bonded with the MMA-TBB. The shear bond (Ø=5 mm) strength was measured. The surface free energies of the specimens were determined by measuring contact angles. The KHF2 and NH4HF2 groups exhibited higher shear bond strength and surface free energy than did the alumina blasting and no treatment groups. Compared with alumina blasting, etching with KHF2 and NH4HF2 exhibited superior bonding ability of mechanical retention to zirconia.