Preparation and Characterization of PMMA/SrBHA Composites for Bone Replacement Applications

Polymethyl methacrylate (PMMA) is a polymer that is a suitable biomaterial for applications such as bone cement and replacement hip joints because it is inert, non-toxic, and has good mechanical properties. Hydroxyapatite (HA) is among the most thoroughly investigated bioceramics because its composition is similar to that of human bone and it has excellent biocompatibility and osteoconductive properties. Moreover, HA can be modified to regulate its physiochemical properties. In this study, boron and strontium were co-substituted into HA (SrBHA) to improve its biological characteristics. Previous studies have shown that strontium can increase bone density, although it negatively affects bone production. Moreover, boron helps to regulate the calcium balance to prevent bone loss. PMMA/SrBHA composites were prepared with different concentrations of SrBHA powder and the effects on the mechanical properties of the composites were investigated. The composites were fabricated using twin-screw extruders and compressed into test specimens using compression molding machinery. When the SrBHA powder concentration was <10 phr, the SrBHA particles were uniformly dispersed throughout the composite via a continuous polymer matrix reaction. Moreover, this concentration produced the greatest increase in compressive strength compared to the sample with no SrBHA (127.4 MPa). The composites were analyzed using energy-dispersive X-ray analysis, Fourier-transform infrared spectroscopy, and X-ray diffraction to determine the dispersion of the reinforced nanoparticles. Scanning electron microscopy (SEM) was used to analyze the dispersion of the SrBHA powder inside the matrix and to determine the causes of the fractures. The SrBHA powder improved the mechanical properties of PMMA, which is critical for applications in biomedical components. The mechanical tests and SEM analysis indicated that PMMA/SrBHA composites could be used for replacement joints and orthopedic implants.