The world of biomaterials has been continuously evolving. Where in the past only mono-material implants were used, the growth in technology and collaboration between researchers from different sectors has led to a tremendous improvement in implant industry. Nowadays, composite materials are one of the leading research areas for biomedical applications. When we look toward hard tissue applications, metal-based composites seem to be desirable candidates. Metals provide the mechanical and physical properties needed for load-bearing applications, which when merged with beneficial properties of bioceramics/polymers can help in the creation of remarkable bioactive as well biodegradable implants. Keeping this in mind, this review will focus on various production routes of metal-based composite materials for hard tissue applications. Where possible, the pros and cons of the techniques have been provided.

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The “stress-shielding” problem, common with metallic implants, may be solved by using biocompatible sandwiches with a polymeric core between two metallic skin sheets. To achieve such sandwiches, a process route has been developed, beginning with the grafting of poly-(methyl-methacrylate) (PMMA) on titanium (Ti) sheets via the “grafting from” technique. Grafting resulted in variable thicknesses of PMMA on the Ti sheets. Hot-pressing was used to prepare semi-finished Ti–PMMA–Ti sandwiches. The adhesion was achieved by the interpenetration between PMMA sheet and the grafted PMMA chains. Investigation was carried out to understand the influence of the grafted PMMA thickness on the adhesion strength. Similar adhesion strengths were found for the sandwiches despite variable grafted PMMA thicknesses, indicating a successful grafting of PMMA on large-scale Ti sheets. The adhesion followed the autohesion theory, where a time-dependent increase in adhesion strength was found for the sandwiches.

A cranio-maxillofacial region contains several bones and serves to protect and support the area, from the brain to the masticatory system. In this paper the clinical and research aspects of craniomaxillofacial biomaterials have been highlighted to serve as a guide into the wide world of their reconstructions. After a quick look into the anatomy, the review focuses on the causes of large bone defects in this region, and how they influence the designing process of the implant. Since it is a large area to unfold, only the maxillary, the mandible and the temporomandibular joints are highlighted. Understanding the biomechanics of mandible and temporomandibular joints is quite important, as it strongly influences the choice of the biomaterial. Thus, the latest techniques implemented to understand the biomechanics of the mandible are also highlighted. Via the finite element analysis, a simulation can help to identify the forces and the movements of the mandible and to predict the possible outcome of the implantation influencing the choice of the biomaterial.

Biocompatible polymers such as polymethyl methacrylate (PMMA), despite fulfilling biomedical aspects, lack the mechanical strength needed for hard-tissue implant applications. This gap can be closed by using composites with metallic reinforcements, as their adaptable mechanical properties can overcome this problem. Keeping this in mind, novel Ti-mesh-reinforced PMMA composites were developed. The influence of the orientation and volume fraction of the mesh on the mechanical properties of the composites was investigated. The composites were prepared by adding Ti meshes between PMMA layers, cured by hot-pressing above the glass transition temperature of PMMA, where the interdiffusion of PMMA through the spaces in the Ti mesh provided sufficient mechanical clamping and adhesion between the layers. The increase in the volume fraction of Ti led to a tremendous improvement in the mechanical properties of the composites. A significant anisotropic behaviour was analysed depending on the direction of the mesh. Furthermore, the shaping possibilities of these composites were investigated via four-point bending tests. High shaping possibility was found for these composites when they were shaped at elevated temperature. These promising results show the potential of these materials to be used for patient-specific implant applications.