Effects of Surface Treatment at the Zirconium-dioxide Veneer Interface

Objectives:  Confusion exists concerning optimal surface preparation of CAD/CAM zirconium-dioxide prosthesis substructures.  The shear bond strength at the substructure-veneer interface of as-milled and sandblasted CAD/CAM processed zirconium-dioxide veneered with various porcelains was investigated.

Methods: KaVo Everest and 3M ESPE Lava systems zirconium-dioxide substructures were fabricated.  Prior to veneer porcelain application, the substructures were either sandblasted with 50µ aluminum-oxide at 50 p.s.i. or left as-milled.  Lava-Ceram, Ceramco-PFZ, Nobel-Rondo, and GC-Initial Zr porcelains were applied following manufacturer's instructions in a uniform 3mm circle.  Load to failure (N) of all 16 groups (n=10) was measured with a Bose Electroforce-3300 at 0.5 mm/min.  Shear bond strengths (MPa) were calculated and analyzed using ANOVA and Tukey HSD, p<0.05.

Results:  Two-way ANOVA of Everest zirconium-dioxide indicated significant effects in porcelain type(p<0.0001), but no difference in surface treatments(p=0.9045) and no difference in surface treatment and porcelain type interaction(p=0.1891).  Post hoc analysis indicated a significant difference in the shear bond strength of Ceramco-PFZ porcelain compared with other porcelains, with no statistical differences occurring among the remaining groups.

Two-way ANOVA of Lava zirconium-dioxide demonstrated significant effects for porcelain(p<0.0001) and surface treatment(p=0.0093), but no difference in surface treatment and porcelain type interaction(p=0.9485).  Post hoc analysis revealed significantly higher shear bond strength among the milled surface compared with sandblasted.  Significantly higher strength for Ceramco-PFZ porcelain was found compared with Lava-Ceram and Nobel-Rondo.  GC was also significantly stronger than Lava-Ceram.

Conclusion: Zirconium-dioxide post milling surface treatment protocols are CAD/CAM system specific. For Everest zirconium-dioxide, surface treatment had no significant effect on shear bond strength; the strength was significantly higher with Ceramco porcelain. For Lava zirconium-dioxide, shear bond strength was significantly higher for as-milled; porcelain type was also significant.

Supported by NIH/NIDCR T32 DEO14678-05, KaVo America, 3M ESPE, Nobel Biocare, Dentsply Ceramco, and University of Iowa College of Dentistry.