Effect of various surface preparations on bond strength of a gingiva-colored indirect composite to zirconia framework for implant-supported prostheses

Effects of dimensions of laser-milled grid-like microslits on shear bond strength between porcelain or indirect composite resin and zirconia

PURPOSE

Zirconia cores and frameworks are widely used in restorative dentistry. Although these structures are veneered with porcelain for esthetic reasons, the use of indirect composite resins (ICRs) is expected to increase in the future. The purpose of this study was to investigate the effects of microslits of different dimensions formed by Nd:YVO 4 laser machining on the bond strength between two types of zirconia (3 mol% yttria-partially stabilized zirconia (Y-TZP) and ceria-partially stabilized zirconia/alumina nanocomposite (Ce-TZP/A)) and porcelain or an ICR.

METHODS

The zirconia disks were assigned as follows: 1) blasted with alumina particles (AB) and 2-4) surface machined with gridded microslits with a width, pitch, and depth of 50, 75, or 100 µm (MS50, MS75, and MS100, respectively). After the bonding of the veneering materials to the disks, half of the specimens veneered with the ICR were subjected to thermocycling (4-60°C, 20000 cycles). All the specimens were subsequently shear tested (n = 10/group).

RESULTS

There was no significant difference between the groups of the disks bonded to porcelain. On the other hand, for the disks bonded to the ICR, the bond strengths of the MS groups after thermocycling were statistically higher than that of the AB group. However, there was no significant difference in the bond strengths of the disks with different microslits.

CONCLUSIONS

Within the study limitations, it can be concluded that, for porcelain, the design of the mechanical retentive structure must be modified. However, for the investigated ICR, a simple gridded pattern can improve the bond strength with zirconia.

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.