Mirror-polished ceria-stabilized zirconia/alumina nanocomposite enhances gingival junctional epithelial cell adhesion

The aim of this study was to determine the optimal surface roughness (Ra) of ceria-stabilized zirconia/alumina nanocomposite (Ce-TZP/Al₂O₃) implants for mouse gingival junctional epithelial cell (JE-1) adhesion and soft tissue sealing in vitro.

Titanium and Ce-TZP/Al₂O₃ disks were prepared, mechanically polished (M), and mirror-polished (Mr). The surface morphology of each disk was evaluated, and the Ra was measured using scanning electron microscopy and atomic force microscopy. JE-1 cells were cultured on each disk, and cell proliferation was assessed by measuring the absorbance using the MTS assay. We also analyzed the expression of the adhesion proteins Laminin-5, Integrin β4, and Cadherin-1 using immunostaining and quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The adhesion strength of the JE-1 cells to each disk was measured using a shaking stimulation test.

M disks had rough surfaces, whereas Mr disks had smooth morphologies. JE-1 cell proliferation was proportional to the culture time, and the Mr disks showed higher values than the M disk. Immunofluorescence and qRT-PCR showed that expression of Laminin-5 and Integrin β4 was higher with Mr disks than with M on the Ce-TZP/Al₂O₃ disks. The oscillatory stimulation test also showed that the adhesive strength of JE-1 cells was significantly higher with Mr than with M on the Ce-TZP/Al₂O₃ disks.

Mirror polishing of Ce-TZP/Al₂O₃ disks enhances epithelial cell proliferation and adhesion more than mechanical polishing. These findings have implications for the optimization of implant surface characteristics to improve epithelial sealing.