PEEK containing titanium dioxide fillers promotes biofilm formation

Polyaryletherketones (PAEKs) are widely used in dentistry due to their high biocompatibility, while their physical and mechanical properties are frequently modified using fillers and additives. Effects of these modifications on biocompatibility and biofilm formation remain unclear. This study investigated the influence of different PAEK compositions on the quantity and composition of biofilms.

Five PAEKs (unfilled PEEK, filled PEEK, pressed PEEK, PEKK, and AKP) and reference materials (titanium, zirconium dioxide, PMMA) were polished to Ra values below 0.2 µm to control for topographical effects. Surface morphology and composition were determined by scanning electron microscopy and wavelength-dispersive X-ray spectroscopy on an electron microprobe (WD-EPMA). Surface free energy (SFE) was analyzed by contact angle measurement. Custom-made intraoral splints with mounted material specimens were worn by 20 participants for 24 h. Biofilm formation was analyzed using microscopy and qPCR. Two PEEK types (filled and unfilled) underwent additional 24-hour exposures by six participants and were analyzed for microbial differences. Additionally, filled and unfilled PEEK were compared to titanium in CCK-8 assays using human fibroblasts.

All materials exhibited homogeneous surface morphology. SFE was significantly higher (p < 0.0005) for all materials compared to titanium, except for zirconium dioxide. Filled PEEK showed increased biofilm formation compared with unfilled PEEK in vitro and in vivo (p < 0.0001), while biofilm composition remained unchanged. Only PEEK containing TiO₂ was associated with increased biofilm formation, without improving fibroblast viability.

TiO₂ in PEEK increased biofilm formation without enhancing fibroblast viability, indicating that material fillers can affect microbial colonization independently of cellular biocompatibility.