Epithelial Cell Adhesion and Protein Expression on TiO₂ Modified Zirconia

Objectives: An adequate mucosal attachment is of a paramount importance when it comes to preventing peri-implant inflammation and improving prognosis of implant treatments. The aim of this study was to compare the effects of bioactive TiO₂-coating to the epithelial cell adhesion and expression of adhesion proteins of epithelial cells cultivated on coated and non-coated zirconia.

Methods: 32 zirconia(Z-CAD, Metoxit) discs (10x10mm) were cut for the research. Half of them were coated with bioactive TiO₂ –coating by using a novel sol-gel derived coating method. To study the epithelial cell attachment, human oral keratinocytes were cultivated on discs (25.000cells/cm2) for 1,3,6 and 24 hours after which the discs were set on TE-buffer(10mmol/L Tris,1 mmol/l EDTA ) and sonicated to release DNA from the cells and the fluorescence of the buffer was detected (BioTek synergy HT). The fluorescence values were compared to standard curve to calculate the total amount of released DNA. In addition, the epithelial cells were cultivated for three days on zirconia discs (25.000cells/ cm²) to define the levels of adhesion proteins. The amounts of expressed integrin α6, paxillin and vinculin were detected by using Western Blot method. What is more, high resolution imaging of actin cytoskeleton and focal adhesion size was accomplished.
Results: There was a clear induction of adhesion proteins on the coated samples (p<0.05). The amount of DNA was greater with coated discs after 1, 3 and 24 hours indicating higher amount of adhered cells on coated vs. non-coated discs. The difference was statistically significant (p<0.05) after 1 and 24 hours.

Conclusions: According to this study, the bioactive TiO₂-coating is able to improve the oral keratinocyte adhesion and increase the formation of adhesion proteins on zirconia surface in vitro. The coating has potential to enhance the mucosal attachment around implant abutments.