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

Abstract

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.

Prosthetic Materials Used for Implant-Supported Restorations and Their Biochemical Oral Interactions: A Narrative Review

“…Besides its unique combination of chemical and physical properties, one of the most important advantages of PEEK (polyether ether ketone) is represented by its potential to show good biocompatibility towards oral tissues [ 80 , 87 , 91 ]. Recently, the study presented by Peng et al confirmed that, under the same culture conditions, PEEK (polyether ether ketone) incubated human oral fibroblasts showed cell adhesion effectiveness, metabolic activity, and pro-inflammatory responses similar to titanium alloy incubated fibroblasts [ 92 ]. Cell adhesion represents a vital molecular process for fibroblasts in order to survive on a material surface; only after the completion of this molecular event can other important cellular phenomena—such as cell proliferation, differentiation, diffusion and migration—take place [ 92 , 93 , 94 , 95 ].…”

“…Recently, the study presented by Peng et al confirmed that, under the same culture conditions, PEEK (polyether ether ketone) incubated human oral fibroblasts showed cell adhesion effectiveness, metabolic activity, and pro-inflammatory responses similar to titanium alloy incubated fibroblasts [ 92 ]. Cell adhesion represents a vital molecular process for fibroblasts in order to survive on a material surface; only after the completion of this molecular event can other important cellular phenomena—such as cell proliferation, differentiation, diffusion and migration—take place [ 92 , 93 , 94 , 95 ]. All these cellular phenomena are strongly correlated with collagen secretion, tissue regeneration, and wound healing.…”

“…All these cellular phenomena are strongly correlated with collagen secretion, tissue regeneration, and wound healing. The substrate roughness, mechanical properties, surface energy, and wettability play key roles in the way cell adhesion occurs [ 92 , 93 , 94 , 95 ]. Both PAEK and PEEK (polyether ether ketone) macromolecules have higher hydrophobicity and lower surface energy compared to ceramic or metallic materials, due to the reduced number of polar functional groups on their surface [ 92 , 93 , 94 , 95 ].…”

“…The substrate roughness, mechanical properties, surface energy, and wettability play key roles in the way cell adhesion occurs [ 92 , 93 , 94 , 95 ]. Both PAEK and PEEK (polyether ether ketone) macromolecules have higher hydrophobicity and lower surface energy compared to ceramic or metallic materials, due to the reduced number of polar functional groups on their surface [ 92 , 93 , 94 , 95 ]. Peng et al reported that in contrast to PEKK, PEEK (polyether ether ketone) (which has more ether groups) had a higher surface energy and lower contact angle.…”

“…Hydrogen bonds cannot form between ether molecules. However, in the ether groups, there are a lot of non-bonding electron pairs on the oxygen atom, able to form hydrogen bonds with -OH or N-H [ 92 , 93 , 94 , 95 ]. Consequently, PEEK (polyether ether ketone) has a relatively high polarity.…”