Abstract:It is generally accepted that a micrometer scale roughness supports the osseointegration of titanium implants. While abrasive technologies can easily be employed to create a micro-topography on titanium surfaces, the preparation of rough ceramic surfaces is more challenging. Typically, abrasive treatments of yttriastabilized tetragonal zirconia polycrystal (Y-TZP) surfaces result in rather smooth topographies (R a < 0.6 μm). Furthermore, when this sandblasting process is performed after firing, a transformation of the tetragonal into the monoclinic phase is observed. Exceeding phase transformation may lead to a decreased flexural strength and an increased brittleness -two highly undesirable processes for a ceramic for load bearing applications. In the present study Y-TZP surfaces were sandblasted between the presintering and the final sintering step. Instead of corundum particles, sintered Y-TZP grit was employed for blasting. By varying the particle size and the sandblasting pressure, moderately rough (R a ~ 1.7 μm) and rough (R a ~ 3 μm) Y-TZP surfaces could be prepared. The resulting rough Y-TZP materials were analyzed with respect to their microstructure, flexural strength and 3D surface topography. The results of the subsequent in vitro and in vivo experiments reveal a cytocompatibility and a bone-implant contact that is well comparable to the reference material titanium SLA (sandblasted, large grit, acid etched).

The aim of this work was to evaluate the influence of specimen preparation and test method on the flexural strength results of monolithic zirconia. Different monolithic zirconia materials (Ceramill Zolid (Amann Girrbach, Koblach, Austria), Zenostar ZrTranslucent (Wieland Dental, Pforzheim, Germany), and DD Bio zx2 (Dental Direkt, Spenge, Germany)) were tested with three different methods: 3-point, 4-point, and biaxial flexural strength. Additionally, different specimen preparation methods were applied: either dry polishing before sintering or wet polishing after sintering. Each subgroup included 40 specimens. The surface roughness was assessed using scanning electron microscopy (SEM) and a profilometer whereas monoclinic phase transformation was investigated with X-ray diffraction. The data were analyzed using a three-way Analysis of Variance (ANOVA) with respect to the three factors: zirconia, specimen preparation, and test method. One-way ANOVA was conducted for the test method and zirconia factors within the combination of two other factors. A 2-parameter Weibull distribution assumption was applied to analyze the reliability under different testing conditions. In general, values measured using the 4-point test method presented the lowest flexural strength values. The flexural strength findings can be grouped in the following order: 4-point < 3-point < biaxial. Specimens prepared after sintering showed significantly higher flexural strength values than prepared before sintering. The Weibull moduli ranged from 5.1 to 16.5. Specimens polished before sintering showed higher surface roughness values than specimens polished after sintering. In contrast, no strong impact of the polishing procedures on the monoclinic surface layer was observed. No impact of zirconia material on flexural strength was found. The test method and the preparation method significantly influenced the flexural strength values.

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