Structural and Morphological Evaluation of Presintered Zirconia following Different Surface Treatments.

ABSTRACT

AIM: The aim of this study was to evaluate the effect of different surface treatments on roughness, grain size, and phase transformation of presintered zirconia. MATERIALS AND METHODS: Surface treatments included airborne particle abrasion (APA) before and after sintering with different particles shape, size, and pressure (50 µm Al2O3, 50 µm glass beads, and ceramic powder). Thirty-five square-shaped presin-tered yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramic slabs (Zenostar ZR bridge, Wieland) were prepared (4 mm height × 10 mm width × 10 mm length) and polished with silicon carbide grit papers #800, 1000, 1200, 1500, and 2000 to ensure identical initial roughness. Specimens were divided into five groups according to surface treatment group I (control) no surface treatment; group II APA 50 µm Al2O3 after sintering; group III APA 50 µm Al2O3 particles before sintering; group IV APA 50 µm glass bead particles before sintering; and group V APA ceramic powder before sintering. Specimens were analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) analyses, and tested for shear bond strength (SBS). Data were statistically analyzed using one-way analysis of variance (ANOVA) followed by post hoc tests for multiple comparisons Tukey's test (a > 0.05). RESULTS: Air abrasion before sintering significantly increased the surface roughness when compared with groups I and III. The highest tetragonal to monoclinic (t-m) phase transformation (0.07%) was observed in group III, and a reverse transformation was observed in presintered groups (0.01%). Regarding bond strength, there was a significant difference between APA procedures pre- and postsintering. CONCLUSION: Air abrasion before sintering is a valuable method for increasing surface roughness and SBS. The abrasive particles' size and type used before sintering had a little effect on phase transformation. CLINICAL SIGNIFICANCE: Air abrasion before sintering could be supposed to be an alternative surface treatment method to air abrasion after sintering.