Surface Properties, Biocompatibility, and Bacterial Adherence of Four Zirconia Variants for Aesthetic Zone Abutments

To evaluate the viability of human gingival fibroblasts (HGFs) and the oral biofilm formation on high-translucent (HT) and ultra-translucent (UT) zirconia, compared to traditional Y-TZP (Tra) zirconia and glazed (GL) zirconia.

Discs of Tra-zirconia, HT-zirconia, UT-zirconia, and GL-zirconia were prepared for analysis. Surface characteristics were investigated by scanning electron microscopy, atomic force microscopy, surface roughness tester, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Raman spectroscopy. HGF's viability was assessed at 1, 3, and 5 days, and cellular morphology was observed at 4 and 24 h. Additionally, Streptococcus mutans proliferation and viability assays (3, 6, and 12 h) along with bacterial morphology and biofilm formation, were evaluated.

GL-zirconia exhibited significantly higher surface roughness than Tra-, HT-, and UT-zirconia (p < 0.0001). UT-zirconia, with approximately 52.3% cubic phase, showed the highest HGFs viability (p < 0.05). The GL-zirconia group demonstrated lower HGFs viability and higher S. mutans adhesion compared to the other three groups. No significant differences in bacterial adhesion were observed among the Tra-zirconia, HT-zirconia, and UT-zirconia groups.

Within the limitations of this in vitro study, ultra-translucent zirconia appears to be a suitable alternative to conventional zirconia for aesthetic zone implant abutments.