Fabrication and Antibacterial Performance of Graded Nano–Composite Biomaterials

Solid freeform fabrication (SFF), also termed as layered manufacturing, produces parts directly from a computer model without part-specific tooling and human intervention (Sachlos et al., 2003; Leong et al., 2003; Kim et al., 2009; Dwivedi and Kovacevic, 2004; Cai et al., 2003; Tian et al., 2002; Guo et al., 2002; Cawley, 1999; Calvert et al., 1998; Alimardani and Toyserkani, 2008; Alemohammad et al., 2007; Li, 2005; Bryant et al., 2003). It has great potential to fabricate functionally graded materials (FGMs). Through selective slurry extrusion (SSE) based technique of SFF, Xu et al. successfully fabricated multi-material dental crown (Xu et al., 2005) and further proposed a novel approach (as shown in Figure 1), termed as equal distance offset (EDO), to representing and process planning for SFF of functionally graded materials so as to meet the requirement of modelling and fabricating 3D complex shaped FGM objects (Xu and Shaw, 2005). In EDO (Xu and Shaw, 2005), a neutral arbitrary 3D CAD model is adaptively sliced into a series of 2D layers. Within each layer, 2D material gradients are designed and represented via dividing the 2D shape into several sub-regions enclosed by iso-composition contours. If needed, the material composition gradient within each of the sub-regions can be further specified by applying the equal distance offset algorithm to each sub-region. Using this approach, an arbitrary-shaped 3D FGM object with linear or non-linear composition gradients can be represented and fabricated via suitable SFF machines. The process planning for SFF of FGM objects is shown in Figure 2. In recent years, the inkjet colour printing based SFF technology has been of great interests in tissue engineering (Calvert et al., 2007; Xu et al., 2006; Saunders et al., 2008; Sanchez et al., 2008; Roth, 2004; Hasenbank et al., 2008; Cui and Boland, 2009), as it can fabricate 3D complex shaped graded material with smooth gradients (Wang and Shaw, 2006). Human teeth have some very good properties such as high hardness and wearability, good heat insulation, high strength, etc. These properties are related to its graded structure. Figure 3 (Tooth anatomy, (2011). http://www.mydr.com.au/first-aid-self-care/toothanatomy) shows a drawing of a healthy tooth cut in half lengthways, which shows the layers of the tooth and its internal structure, as well as how the tooth relates to the gum and surrounding jaw bone.