Crystallographic and morphological analysis of sandblasted highly translucent dental zirconia

Objective: To assess the influence of alumina sandblasting on four highly translucent dental zirconia grades. Methods: Fully sintered zirconia disk-shaped specimens (15-mm diameter; 0.5-mm thickness) of four highly translucent yttria partially stabilized zirconia (Y-PSZ) grades (KATANA HT, KATANA STML, KATANA UTML, Kuraray Noritake; Zpex Smile, Tosoh) were sandblasted with 50-μm alumina (Al₂O₃) sand (Kulzer) or left ‘as-sintered’ (control) (n = 5). For each zirconia grade, the translucency was measured using a colorimeter. Surface roughness was assessed using 3D confocal laser microscopy, upon which the zirconia grades were statistically compared for surface roughness using a Kruskal–Wallis test (n = 10). X-ray diffraction (XRD) with Rietveld analysis was used to assess the zirconia-phase composition. Micro-Raman spectroscopy was used to assess the potentially induced residual stress. Results: The translucency of KATANA UTML was the highest (36.7 ± 1.8), whereas that of KATANA HT was the lowest (29.5 ± 0.9). The ‘Al₂O₃-sandblasted’ and ‘as-sintered’ zirconia revealed comparable surface-roughness Sa values. Regarding zirconia-phase composition, XRD with Rietveld analysis revealed that the ‘as-sintered’ KATANA UTML contained the highest amount of cubic zirconia (c-ZrO₂) phase (71 wt%), while KATANA HT had the lowest amount of c-ZrO₂ phase (41 wt%). KATANA STML and Zpex Smile had a comparable zirconia-phase composition (60 wt% c-ZrO₂ phase). After Al₂O₃-sandblasting, a significant amount (over 25 wt%) of rhombohedral zirconia (r-ZrO₂) phase was detected for all highly translucent zirconia grades. Significance: Al₂O₃-sandblasting did not affect the surface roughness of the three highly translucent Y-PSZ zirconia grades, but it changed its phase composition.