Osseointegration of 3D-Printable Polyetheretherketone–Magnesium Phosphate Bioactive Composites for Craniofacial and Orthopedic Implants

Polyetheretherketone (PEEK) is a high-performance polymer material for developing varying orthopedic, spine, cranial, maxillofacial, and dental implants. Despite their commendable mechanical properties and biocompatibility, the major limitation of PEEK implants is their low affinity to osseointegrate with the neighboring bone. Over the last two decades, several efforts have been made to incorporate bioactive components such as bioceramic particles in PEEK to enhance its osseointegration capacity. However, one major limitation is that the bioceramic particles embedded in the PEEK matrix can degrade over time, compromising the implant's long-term bioactivity and mechanical properties. To address this limitation, in this study, we utilized a unique bioceramic known as amorphous magnesium phosphate (AMP). AMP is a metastable phase of magnesium phosphate that nanocrystallizes in a physiological medium to stable bioactive phases exhibiting low degradation kinetics and high bioactivity. Thus, based on this property of AMP, we hypothesize that AMP-PEEK composites will exhibit sustained biodegradation kinetics, help maintain long-term osseointegration, and inhibit mechanical property degradation. Herein, we reported on a detailed in vitro degradation analysis of the developed AMP-PEEK composite 3D-printable filaments and the osseointegration capacity when implanted in a rat femoral model. The AMP-PEEK composite demonstrates controlled degradation kinetics, with tensile strength progressively decreasing from 120 to 70 MPa over a 28-day period due to hydrolytic degradation, which aligns with its role as a bioresorbable material. Notably, our findings confirm that AMP-PEEK composite osseointegration is on par with clinical gold-standard titanium implants. Thus, this study establishes a unique magnesium phosphate and PEEK-based bioactive composite material with promising potential for developing standalone dental and craniofacial implants.