I-C. Kang et al./ Materials Letters 59(2005)69-73 Fig. 4. The inverted microscopic finding of MG-63 cells cultured on 6-well plate(a)and second passed fibrous monolithic Al2O3 porous body for 14 days(b). suitable to explore the attachment and growth of osteoblasts Control of the grain size to nm regime is important for (not shown). the behavior of cell attachment because reducing the grain size induces an increase in hydrophilicity and surface reactivity of the bioceramics material. Webster et al 4. Discussion reported that cell contact angles were decreased as the grain size of Al2O3 increased, in which the angles were, The potential advantage offered by a porous Al2O3 respectively, 18.6, 10.8, and 6. 4 at the grain size of implant is the mechanical stability of the highly convoluted 177, 49, and 23 nm [17]. The decrease in the contact angle interface developed when bone grows into the pores of the corresponds to an increase in surface aqueous wettability ceramics. However, the porous ceramics should be com- Furthermore, the grain size refinement increases the surface plied with the mechanical property enough to sustain the roughness and surface area, resulting in an improvement of pore structures in shape and size as well as the load when cell attachment. Using the fibrous monolithic process, the implanted in the body. It is therefore important to control the size of grain could be reduced to about 150 nm after the grain size of matrix material because the mechanical forth pass and 21 nm after the fifth pass at this experimental property increases as the grain size decreases. The fibrous condition. Those sizes are also controllable by varying the monolithic process is an efficient process suitable for a area reduction ratio fabrication of continuously porous ceramic body with an Considering the average MG-63 cell size of 10 um, the easy control of the grain size as well as the pore size insufficient growth of the cells in the third passed body [14,15] having pores about 40 um makes it confusing to under ●e Fig. 5. The morphology of MG-63 cells proliferating on the top(a and b) and bottom (c and d) surfaces of the second passed Al,, porous body for 5 days(asuitable to explore the attachment and growth of osteoblasts (not shown). 4. Discussion The potential advantage offered by a porous Al2O3 implant is the mechanical stability of the highly convoluted interface developed when bone grows into the pores of the ceramics. However, the porous ceramics should be com￾plied with the mechanical property enough to sustain the pore structures in shape and size as well as the load when implanted in the body. It is therefore important to control the grain size of matrix material because the mechanical property increases as the grain size decreases. The fibrous monolithic process is an efficient process suitable for a fabrication of continuously porous ceramic body with an easy control of the grain size as well as the pore size [14,15]. Control of the grain size to nm regime is important for the behavior of cell attachment because reducing the grain size induces an increase in hyfrophilicity and surface reactivity of the bioceramics material. Webster et al. reported that cell contact angles were decreased as the grain size of Al2O3 increased, in which the angles were, respectively, 18.68, 10.88, and 6.48 at the grain size of 177, 49, and 23 nm [17]. The decrease in the contact angle corresponds to an increase in surface aqueous wettability. Furthermore, the grain size refinement increases the surface roughness and surface area, resulting in an improvement of cell attachment. Using the fibrous monolithic process, the size of grain could be reduced to about 150 nm after the forth pass and 21 nm after the fifth pass at this experimental condition. Those sizes are also controllable by varying the area reduction ratio. Considering the average MG-63 cell size of 10 Am, the insufficient growth of the cells in the third passed body having pores about 40 Am makes it confusing to under￾Fig. 4. The inverted microscopic finding of MG-63 cells cultured on 6-well plate (a) and second passed fibrous monolithic Al2O3 porous body for 14 days (b). Fig. 5. The morphology of MG-63 cells proliferating on the top (a and b) and bottom (c and d) surfaces of the second passed Al2O3 porous body for 5 days (a and c) and 10 days (b and d). 72 I.-C. Kang et al. / Materials Letters 59 (2005) 69–73