The State-of-the-Art Development of New Dental Implant Based on Bioengineered PEEK Material

Abstract

Dental implants have become the gold standard treatment to replace the missing teeth in dental practice which increased the demands tremendously. Titanium dental implants are routinely used, but they are associated with certain limitations mainly resorption of the alveolar crest due to the mismatch between the elastic modulus of titanium and bone. Titanium dental implants also cause streak artefacts with radiographic imaging. The metallic grey colour of titanium which shows through the thin gingiva is unpleasing aesthetically. Further innovation and consideration of alternative implants are therefore required to deal with these limitations. Polyetheretherketone (PEEK) was considered a potential alternative to titanium implants. Despite the fact that PEEK has excellent biocompatibility, stability and bone-like stiffness, its high hydrophobicity prevents osseointegration. Therefore, this research investigated a novel approach to modify and improve the surface bioactivity and explored, in-vivo, its osseointegration potential in preparation for clinical applications. ions.The main focus of this research was to evaluate the ability of bioengineered PEEK to induce and promote bone formation in in-vitro and to achieve osseointegration in a preclinical model. The surface of PEEK was modified by the application of osteoinductive coating consisting of plasma polymerised poly-ethylacrylate (p-PEA), fibronectin and bone morphogenetic protein 2 (BMP-2). The surface characterisation of the coated PEEK was investigated using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and water contact angle (WCA). Also, the release of growth factor BMP-2 over 14 days was measured. The in-vitro study also explored the cell response and differentiation of human mesenchymal stem cells (MSCs) to the bioengineered PEEK surfaces. Cell adhesion and osteogenic differentiation of the cells were evaluated using Coomassie blue, alkaline phosphatase (ALP) activity and staining. Mineralisation was assessed by Alizarin red and von Kossa staining after 28 days. The in-vitro study showed that PEEK bioactivity was increased significantly and confirmed the osteogenic differentiation of MSCs on its bioengineered surface. III The in-vivo study was carried out at the Small Animals Research Unit-Biological Services, University of Glasgow. This part of the study was carried out on fourteen healthy New Zealand white male rabbits in a randomised, controlled split-mouth design. In each rabbit, two implants were inserted on palatal side of the anterior part of the maxilla; a bioengineered PEEK implant on one side, and a standard titanium implant “control” on the other side. Animals were sacrificed after 8 weeks to investigate the osseointegration. Standard 3D radiographic assessments, micro-computed tomography scanning (μ-CT) and bone mineral content were analysed to investigate the osseointegration of the implants. Bone volume to total volume (BV/TV), bone mineral density (BMD) and bone-to-implant contact (BIC), were measured using μ-CT. The study confirmed the direct bone contact on the bioengineered PEEK implants. BV/TV was significantly higher in the bioengineered PEEK implants (21.7 ± 4.05 %) compared to titanium implants (17.43 ± 6.72 %), (P<0.005). No statistically significant difference was noted in BMD between bioengineered PEEK (0.32 ± 0.03 g.cm-3) and control implants (0.38 ± 0.14 g.cm-3). The novel surface functionalisation improved the bioactivity of PEEK and achieved osseointegration of bioengineered implants in a rabbit model. The innovative animal model and the performed surgical technique of this study proved safe, reproducible, standardisable and easy to conduct. The findings of this study prepare the way for the clinical application of bioengineered PEEK as new dental implants that has the potential to overcome the limitation of titan