UV Treatment Restores Degraded Bioactivity of Titanium After Polishing

Objectives: Titanium-based implant abutments and tissue bars are polished during the finalization. We hypothesized that polishing degrades the bioactivity of titanium and, if so, photofunctionalization-grade UV treatment can alleviate the adverse effect.
Methods: Three groups of titanium disks were prepared; machine surface (CONT), polished surface (PO), polished surface followed by UV treatment (PO-UV). Polishing was performed by sequential use of green stone and silicon rubber burs. UV treatment was performed using a UV device for 12 minutes. Hydrophobicity/hydrophilicity was examined by the contact angle of ddH2O. Surface morphology and chemistry of titanium were examined by SEM and XPS, respectively. Human epithelium cells were seeded on titanium disks. The number of cells attached, spreading behavior of cells, and retention on titanium surfaces were examined.
Results: PO group showed structures in undefined form and stain-like discoloration caused by uneven release of electron signal, whereas CONT group was free of such foreign deposits. PO group showed a significantly increased percentage of surface carbon compared to CONT group. The carbon percentage on PO-UV group was even lower than that on CONT group. Silicon element, which was exclusively detected on PO group, was not seen on PO-UV group. Both CONT and PO groups were hydrophobic, whereas PO-UV group was hydrophilic. The number of attached cells after 24 hours was 60% lower on PO group than CONT group. The number of attached cells on PO-UV group was even higher than that on CONT group. The size and perimeter of cells, which was significantly reduced on PO group, were fully restored on PO-UV group. The number cells remained adherent after mechanical detachment was reduced to half on PO group compared to CONT group. Adherent cells on PO-UV group was 2-time more than on CONT group.
Conclusions: Polishing titanium causes structural and chemical contamination, which significantly compromised the attachment and retention of epithelial cells. UV treatment of polished titanium restored the adverse effects and even outperformed the inherent bioactivity of original titanium.