Full-contour Y-TZP ceramic surface roughness effect on synthetic hydroxyapatite wear

To investigate the effects of polishing techniques on the surface roughness of Y-TZP ceramic and on the wear behavior of synthetic hydroxyapatite (HA).

Thirty-two full-contour Y-TZP (Diazir(®)) sliders (φ=2 mm × 1.5 mm in height) were manufactured using CAD/CAM, embedded in acrylic resin using brass holders, and randomly allocated into four groups (n=8): according to the finishing/polishing procedure: G1-as-machined, G2-glazed, G3-diamond bur finishing and G4-G3+OptraFine(®) polishing kit. Thirty-two sintered HA disks (φ=13 mm × 2.9 mm in height) were similarly mounted in brass holders. Y-TZP sliders baseline surface roughness values (Ra and Rq, in μm) were recorded using a non-contact profilometer (Proscan 2000). A two-body pin-on-disc wear test was performed. HA height (μm) and volume (mm(3)) losses were measured. Y-TZP height loss was measured using a digital micrometer. One-way ANOVA was used to determine the effect of the polishing techniques on the surface roughness. Comparisons between groups for differences in antagonist height loss/volume, and slider height loss were performed using one-way ANOVA. Statistical significance was set at α=0.05.

Roughness measurements showed significant differences (p=0.0001) among the surface treatments with G1 (Ra=0.84, Rq=1.13 μm) and G3 (Ra=0.89, Rq=1.2 μm) being the roughest, and G2 (Ra=0.42, Rq=0.63 μm) the smoothest (p=0.0001). Y-TZP slider height loss was highest for the glazed group (35.39 μm), and was lowest for the polished group (6.61 μm) (p=0.0001). Antagonist volume and height losses for groups (G1-G3) were similar, while the polished group (1.3 mm(3), 14.7 μm) showed significant lower values (p=0.0001).

Although glazed zirconia provides an initially smooth surface, significantly increased antagonist wear was observed compared to the polished Y-TZP zirconia surface.