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

Objective: To investigate the effects of polishing techniques on the surface roughness of Y-TZP ceramic and on the wear behavior of synthetic hydroxyapatite (HA). Methods: Thirty-two full-contour Y-TZP (Diazir®) sliders (φ =2mm×1.5mm 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 =13mm×2.9mm 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 (mm3) 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. Results: Roughness measurements showed significant differences (p =0.0001) among the surface treatments with G1 (Ra=0.84, Rq=1.13μm) and G3 (Ra=0.89, Rq=1.2μm) being the roughest, and G2 (Ra=0.42, Rq=0.63μm) the smoothest (p =0.0001). Y-TZP slider height loss was highest for the glazed group (35.39μm), and was lowest for the polished group (6.61μm) (p =0.0001). Antagonist volume and height losses for groups (G1–G3) were similar, while the polished group (1.3mm3, 14.7μm) showed significant lower values (p =0.0001). Significance: Although glazed zirconia provides an initially smooth surface, significantly increased antagonist wear was observed compared to the polished Y-TZP zirconia surface. [ABSTRACT FROM AUTHOR]