THREE-DIMENSIONAL SHAPE CONTROL OF IMPLANT DEVICES - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 582

manually carved to fit to deformities during surgery. This process is
often time consuming and laborious, being associated with low pre-
cision and a poor aesthetic outcome. 6 These situations call for the
development of the artificial bones that can replace autografts and
allografts.
Currently, among the three major biomaterials (polymers, met-
als, and ceramics), ceramics is most widely used; calcium phos-
phates are the most popular materials for artificial bones. 7 , 8 The
choice of the calcium phosphates is reasonable because approxi-
mately 70% of bone in our body is made of the calcium phosphates,
amounting to about 1.7 kg for a male weighing 60 kg. 9 Therefore,
their biocompatibility and biosafety were, in a sense, already tested
in the living body. The calcium phosphates are metabolized and
degraded by the endogenous system for bone remodeling, although
thespeedofdegradationvariesdependingontheirparticlesizeand
form. The calcium phosphates are naturally osteoconductive. 9 This
uniquecombinationoftheexcellentmaterialproperties suitablefor
the artificial bones gives the calcium phosphates a big edge over the
other materials.
The artificial bones made of the calcium phosphates are supe-
rior to autografts and allografts in biosafety, unlimited quantity, and
low invasiveness because they are made from limestone and min-
eral phosphates, are thus free from contamination by pathogens,
and do not require bone collection from donor sites. 10 However,
the artificial bones that have been developed and used so far in
clinical settings come in relatively simple, uniform shapes, requir-
ing cumbersome and low-precision shape adjustment by surgical
operators during surgery. In addition, these artificial bones are
usually sintered after fabrication in order to increase mechani-
cal strength and thereby withstand surgical procedures. 11 , 12 The
postfabrication sintering process, however, causes contraction in
size and often decreases biodegradability by increasing the cal-
cium phosphates in glass state. 13 Therefore, novel artificial bones
are in need that have better shape compatibility to deformi-
ties, appropriate mechanical strength without the postfabrication
sintering, and biodegradability. We have conceived that the key to
meeting all demands may lie in the innovation of the 3D fabrication
technology. 14