The increasing use of biodegradable devices in tissue engineering and regenerative medicine means it is essential to study and understand their degradation behaviour. Accelerated degradation systems aim to achieve similar degradation profiles within a shorter period of time, compared with standard conditions. However, these conditions only partially mimic the actual situation, and subsequent analyses and derived mechanisms must be treated with caution and should always be supported by actual long-term degradation data obtained under physiological conditions. Our studies revealed that polycaprolactone (PCL) and PCL-composite scaffolds degrade very differently under these different degradation conditions, whilst still undergoing hydrolysis. Molecular weight and mass loss results differ due to the different degradation pathways followed (surface degradation pathway for accelerated conditions and bulk degradation pathway for simulated physiological conditions). Crystallinity studies revealed similar patterns of recrystallization dynamics, and mechanical data indicated that the scaffolds retained their functional stability, in both instances, over the course of degradation. Ultimately, polymer degradation was shown to be chiefly governed by molecular weight, crystallinity susceptibility to hydrolysis and device architecture considerations whilst maintaining its thermodynamic equilibrium.

Making models based on patient data is an obvious application for rapid prototyping technology. Whilst many doctors and surgeons have used this technology successfully, it is by no means a standard for diagnosis or integration with medical procedures. There are numerous reasons for this related to complexity, cost, speed and other performance criteria. This paper will illustrate a number of instances where RP and associated technology has been successfully used for medical applications. These examples will serve to illustrate the diversity of tasks in which RP can benefit the medical community and form the basis for discussion on how medical RP technology should develop.

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Selective laser sintering (SLS) has been investigated for the production of bioactive implants and tissue scaffolds using hydroxyapatite (HA) reinforced polyethylene (HDPE) composites with the aim of achieving the rapid manufacturing of customised implants. Single layer and multilayer block specimens made of HA-HDPE composites with 30 vol% and 40 vol% HA were sintered successfully using a CO 2 laser sintering system. Laser power and scanning speed had a significant effect on the sintering behaviour. The degree of particle fusion and porosity were influenced by the laser processing parameters, hence control can be attained by varying these parameters. Moreover, the SLS processing allowed exposure of HA particles on the surface of the composites and thereby should provide bioactive products. Pores existed in the SLS fabricated composite parts and at certain processing parameters a significant fraction of the pores were within the optimal sizes for tissue regeneration. The results indicate that the SLS technique has the potential not only to fabricate HA-HDPE composite products, but also produce appropriate features for their application as bioactive implants and tissue scaffolds.