Three-Body Wear of Glazed and Veneered Zirconia

Objective: To evaluate three-body wear of glazes, applied to dental zirconia, with different coefficients of thermal expansion.

Methods: Yttria-stabilized zirconia (YSZ) plates (12x15x2mm - e.max ZirCAD, Ivoclar Vivadent, Amherst, NY) were divided into 4 groups (n=8/group): 1) YSZ, surface polished through 1200 grit silicon carbide paper (Control), 2) YSZ (1mm thick), veneered (1mm thick - e. max Ceram, Ivoclar Vivadent, Amherst, NY), polished through 600 grit silicon carbide paper, then glazed (e.max Ceram, Ivoclar Vivadent, Amherst, NY), 3) YSZ, glazed (e.max Ceram, Ivoclar Vivadent, Amherst, NY), 4) YSZ, glazed (Empress Universal, Ivoclar Vivadent, Amherst, NY). 

Groups were tested in three-body wear using a Leinfelder-style wear tester with a polyacetal antagonist (Ø=6 mm) and artificial food bolus with a 1:1 weight ratio of poly(methyl-methacrylate) beads and de-ionized water. Groups were tested at 0, 100,000, 200,000, and 400,000 cycles with an applied contact load of 75 N.

Surface roughness, wear depth, and volumetric loss were measured after each interval using a stylus profilometer. 3D surface images (profilometer) and scanning electron micrographs of specimens were obtained after each interval. The effect of cycles on properties was evaluated using one-way ANOVA with a Tukey's test for multiple comparisons if groups were significant (p < 0.05).

Results: Only Group 1 exhibited significance in surface roughness over time. Group 1 was the only group to show a significant decrease in gloss over time; however Group 1 was significantly greater in gloss than other groups at each interval.  Only Group 2 showed significance in wear depth and volume loss after baseline.  After baseline, Group 2 exhibited significantly greater wear depths and volume losses after each interval when compared to other groups.

Conclusion: Wear of glazes on dental zirconia was observed to be independent of thermal expansion coefficient of glazes.