In Vitro Assessment of the Cell Metabolic Activity, Cytotoxicity, Cell Attachment, and Inflammatory Reaction of Human Oral Fibroblasts on Polyetheretherketone (PEEK) Implant–Abutment

The purpose of this research is to compare the cytotoxicity of polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) with conventional dental implant–abutment materials, namely titanium alloy (Ti-6Al-4V) and yttria-stabilized tetragonal zirconia polycrystal (Y-TZP), to evaluate the cell metabolic activity, cytotoxicity, and inflammation potential of human oral fibroblasts (HOF) on these materials. Disk-shaped specimens were designed and prepared via a dental computer-aided manufacturing technology system. Surface topography, roughness, and free energy were investigated by atomic force microscope and contact angle analyzer; cell metabolic activity and cytotoxicity by MTT assay; and morphological changes by scanning electron microscopy (SEM). The effect of pro-inflammatory gene expression was evaluated by RT-qPCR. The obtained data were analyzed with one-way analysis of variance and post-hoc Tukey’s honest significant difference tests. PEEK and PEKK exhibited higher submicron surface roughness (0.04 μm) and hydrophobicity (>80°) than the control. Although the cell activity of PEEK was lower than that of Ti-6Al-4V and Y-TZP for the first 24 h (p < 0.05), after 48 h there was no difference (p > 0.05). According to the cell cytotoxicity and the pro-inflammatory cytokine gene expression assays, there was no difference between the materials (p > 0.05). SEM observations indicated that HOF adhered poorly to PEKK but properly to Ti-6Al-4V, Y-TZP, and PEEK. PEEK and PEKK show comparable epithelial biological responses to Ti-6Al-4V and Y-TZP as implant–abutment materials. Between the two polymeric materials, the PEEK surface, where the HOF showed better cell metabolic activity and cytotoxicity, was a more promising implant–abutment material.