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. •Mirror polishing enhances epithelial cell adhesion on Ce-TZP/Al₂O₃ disks•Increased expression of adhesion proteins observed on mirror-polished Ce-TZP/Al₂O₃•Adhesive strength of epithelial cells significantly improved with mirror polishing•Study provides insights for optimizing dental implant surface characteristics