Selective laser sintering of hydroxyapatite-polyamide composites

Bone loss due to surgery, disease, accidents, or ageing, can result in a functional handicap and cosmetic differences. Bone replacement material may be used to fill the fracture space and bridge the defect, thus regaining continuity between bone tissue. The importance of internal geometry for bone regeneration has been highlighted in previous research. The fabrication and control of such structures by traditional manufacturing techniques is extremely limited. This thesis discusses the manufacture of hydroxyapatite-polyamide composites with complex internal structures using Selective Laser Sintering (SLS) for producing bone implants. This work highlights the importance of optimised fabrication parameters and material properties for the production of such structures. This work began by identifying a suitable polymer for the composite material and by developing a bespoke selective laser sintering system. Later, methods of assessing the complex structures produced by SLS were established. These were then used to study the effects of fabrication parameters and material properties on the complex structures and their suitability for bone implants. An understanding of the mechanisms and causes has allowed greater control over the structures. This work has shown that the capability of successfully sintering HA-Polyamide parts was greatly affected by the amount of HA in the composite material. From this, the highest possible HA content was determined. Sintering results have shown that layer thickness has the greatest in influence on the internal structures of sintered parts, leading to the proposition that the incorporation of layer thickness into the energy density equation is more significant than previously stipulated