Biomedical Engineering Reference
In-Depth Information
orthophosphate precipitates are occasionally called “organoapatites”
[533, 958].
1.7
Conclusions and Outlook
By the end of the twentieth century, it became clear that calcium
orthophosphate biomaterials and bioceramics by themselves could
not give a complete response to the clinical needs for artificial
implants. Biomaterials with more demanding properties were
required. Namely, in 1998, Prof. Larry L. Hench published a forecast
for the future of biomaterials development [959], where he noted that
available that time bioactive materials (calcium orthophosphates,
bioactive glasses and glass ceramics) had already improved
prostheses lifetime but, unfortunately, any type of prosthesis had
mechanical limitations. As the solution, he proposed that biomaterial
researchers would need to focus on tissue regeneration instead of
tissue replacement. A working hypothesis was announced: “long-
term survivability of prosthesis will be increased by the use of
biomaterials that enhance the regeneration of natural tissues”
[959]. One path to follow is the regeneration of bone using calcium
orthophosphate scaffolds that mimic the structure of biological
apatite, bond to bone and in some cases activate the genes within
bone cells to stimulate new bone growth [960-962]. Thus, more than
10 years ago Prof. Hench predicted a rapid development of tissue
engineering field, where calcium orthophosphates play an auxiliary
role. The history has shown that tissue engineering, indeed, is a very
rapidly developed field of science and research [963].
However, what can be said about calcium orthophosphates
themselves? The major questions on chemistry, crystallization,
ion-substitution, crystallography, thermodynamics and phase
relationships for the chemically pure calcium orthophosphates
have been answered in the twentieth century. Some important
topics for DCPD and CDHA have been additionally investigated
in the field of self-setting calcium orthophosphate formulations
(Chapter 5). Conversely, calcium orthophosphates of biological
origin, including the control of their morphology and interaction
of calcium orthophosphate bioceramics with various bioorganic
compounds are not well investigated yet. The same is valid for the
nanocrystalline (Chapter 3) and amorphous (Chapter 2) samples of
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