Biomedical Engineering Reference
In-Depth Information
carbon are inert bioceramics. Certain glass ceramics are dense
hydroxyapatites (9CaO
·
Ca(OH)
2
·
3P
2
O
5
) semi-inert (bioactive), and
calcium phosphates, aluminum-calcium phosphates, coralline, tri-
calciumphosphates(3CaO
·
P
2
O
5
),zinc-calcium-phosphorousoxides,
zinc-sulfate-calcium phosphates, ferric-calcium-phosphorous
oxides, and calcium aluminates are resorbable ceramics.
8
Among
these bioceramics, synthetic apatite and calcium phosphate miner-
als, coral-derived apatite, bioactive glass, and demineralized bone
particle (DBP) will be introduced in this section since they are
widely used in thehard-tissue engineeringarea.
1.2.2.1 Calcium phosphate
Synthetic, crystalline calcium phosphate can be crystallized into
salts such as hydroxyapatite and
β
-whitlockite, depending on the
Ca:P ratio, which are very tissue compatible and are used as
bone substitutes in a granular, sponge form or a solid block. The
apatiteformedwithcalciumphosphateisconsideredcloselyrelated
to the mineral phase of bone and teeth. Chemical composition
of crystalline calcium phosphate is a mixture of 3CaO
·
P
2
O
5
,
9CaO
·
Ca(OH)
2
·
3P
2
O
5
and calcium pyrophosphate (4CaO
·
P
2
O
5
). The
active exchange of ions that occurs on the surface leads to the
exchanging composition of mineral.
9
Also, the delivery of some
elements to the new bone will form at the interface between the
materials and the osteogenic cells when the porous ceramic scaf-
folds are implanted in the body with or without cells for the tissue-
engineered bone.
1.2.2.2 Tricalcium phosphate
Tricalcium phosphate is the rapidly resorbable calcium phos-
phate ceramic resulting in 10 to 20 times resorption, faster than
hydroxyapatite.
10
Porous tricalcium phosphate may stimulate local
osteoblasts for new bone formation. Injectable calcium phosphate
cement containing
β
-tricalcium phosphate, dibasic dicalcium phos-
phate, and tricalcium phosphate monoxide was investigated for the
treatment of distal radius fractures. Calcium sulfate hemihydrate
(plasterofParis)asasyntheticgraftmaterialwasalsotestedforthe
tissue-engineered bone.
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