Synthesis of Light Curable Degradable Materials for on Demand Manufacturing of Maxillofacial Implants

Reconstruction of the head and neck region is usually the result of trauma such as road traffic accidents or disease, in particular head and neck cancer (a highly aggressive cancer and also the 4th most prevalent in males. It also is one of the few cancer types that is increasing in prevalence with a 25% increase in the last decade) and this can result in significant loss of physiological function as well as disfigurement, which can lead to a wide range of chronic, long-term psychological problems. Methods for reconstruction can include bone grafts including significant volume allografts and synthetics as well as utilisation of complex metal based plate and screw systems. Bone grafting, depending on the extent of tissue needed for reconstruction can involve major harvesting and subsequent reimplantation of for example whole ribs. It is clear there is huge scope to improve on current technologies and methodologies.

Additive manufacturing or 3D printing has come of age and offers many advantages over more traditional manufacturing methods. One of the major benefits is that it allows the production of one-off components to be produced and thus lends itself readily to the production of custom fit implants. Most of the print methods use powder based methods and fusion techniques such as laser sintering to produce the final device. These fusion methods are useful as they allow a wider range of materials to be processed compared to extrusion-based methods. Utilisation of chemical cure systems might be an option but this would require premixing prior to extrusion which introduces its own complexity, as well as toxicity issues with initiators. However, 3D printing is still in the early stages of being fully adopted for implant device use as it still has some technical hurdles to overcome: (1) there is a very limited range of materials available that can be printed at a reasonable spatial resolution, are degradable and can be command set/cured and (2) many of the materials currently being investigated for fused deposition modelling, can suffer from particle debris that can be loosely adherent to the printed implant device post printing.

There are very few groups in the UK focusing on the development of radically new materials for additive manufacturing. One option we are pursuing is to develop a number of different polymer systems that are light curable and designing from first principals, i.e. defining the needs and then designing the monomer. Work within our department has produced a range of highly innovative, reactive and bioactive degradable composite materials that can be polymerised via a light cure route. This offers significant advantages over current systems in that it can be supplied sterile and ready to print in a cartridge format allowing on demand printing of the device, sterile and ready to implant. One of the other factors to be borne in mind in this area is that whilst there is a significant push in the field of additive manufacturing for highly accurate (near nett shape) devices, for maxillofacial use this is not a driver, as the device to be implanted will be defined via CT and/or MRI datasets which have an inherent resolution limit of around 0.5-1mm, well within the capabilities of the manufacturing system we propose.