TiO₂-Modified Zirconia Surface Improves Epithelial Cell Attachment

Purpose: Good cell adhesion is an important prerequisite for soft tissue attachment on implant abutment or crown surfaces. The aim of this study was to evaluate the adhesion and proliferation of human epithelial cells on sol-gel-derived TiO₂-coated and noncoated zirconia. Materials and Methods: Altogether, 56 zirconia disks (Z-CAD, Metoxit) were fabricated for this study. Half of the disks were coated with a sol-gel-derived TiO₂ coating (MetAlive, ID Creations). The rest of the disks were noncoated and formed the control group. Surface properties of the disks were characterized by contact angle measurements and surface free energy (SFE) calculation. The cell adhesion was tested by cultivating epithelial cells (20,000 cells/cm²) on the experimental disks for 1, 3, 6, and 24 hours, after which the fluorescence of the samples was measured (BioTek synergy HT). The amount of cells was detected by comparing the fluorescence value to the standard curve. In addition, the proliferation was studied by growing epithelial cells (25,000 cells/cm²) for 1, 3, and 7 days. The number of cells was calculated by defining the absorbance of the samples (Multiskan EX, Thermo Labsystems), followed by a comparison with the standard curve. Finally, the samples were processed for light microscopy. Results: TiO₂-coated disks were significantly more hydrophilic with higher total SFE than noncoated disks (P .05). The amount of epithelial cells was greater on TiO₂-coated disks than on controls after 24 hours (P .05). Regarding cell proliferation, the difference was statistically significant (P .05) on days 3 and 7. Light microscope evaluation confirmed viable cells, which were in immediate close contact with both substrate surfaces. The cell layers on the coated disks appeared to be more uniform and cell rich than the layers on noncoated disks. Conclusion: This study indicated that TiO₂ coating improves epithelial cell attachment and proliferation on zirconia surfaces. This has good potential to enhance formation of the epithelial junction to the coated zirconia surfaces. Keywords: abutment, epithelial cell, hydrophilicity, implant, sol-gel coating, TiO2