Biomedical Engineering Reference
In-Depth Information
solubility data in ref. [220]. Furthermore, an ability of β-TCP to store
an electrical charge by electrical polarization was studied and this
material was found to have a suitable composition and structure for
both ion conduction and charge storage [221].
Pure β-TCP never occurs in biological calcifications. Only the mg-
substituted form called whitlockite [222] (β-TCmP—β-tricalcium
magnesium phosphate, β-(Ca,mg)
) is found in dental calculi
and urinary stones, dentineal caries, salivary stones, arthritic
cartilage, as well as in some soft-tissue deposits [27, 83-85, 229-232].
However, it has not been observed in enamel, dentine, or bone. In
biomedicine, β-TCP is used in calcium orthophosphate bone cements
[233-238] and other types of bone substitution bioceramics [206,
239-246]. Dental applications of β-TCP are also known [247]. Pure
β-TCP is added to some brands of toothpaste as a gentle polishing
agent. Multivitamin complexes with calcium orthophosphate are
widely available in the market and β-TCP is used as the calcium
phosphate there. In addition, β-TCP serves as a texturizer, bakery
improver and anti-clumping agent for dry powdered food (flour,
milk powder, dried cream, cocoa powder). Besides, β-TCP is added as
a dietary or mineral supplement to food and feed, where it is marked
as E341 according to the European classification of food additives.
A prenatal development of rats during gestation was found to be
sensitive to E341 (TCP) exposure [248]. There is a good review
on the toxicological properties of inorganic phosphates, where the
interested readers are referred to [249]. Occasionally, β-TCP might
be used as inert filler in pelleted drugs. Other applications comprise
porcelains, pottery, enamel, using as a component for mordants and
ackey, as well as a polymer stabilizer [134]. β-TCP of a technical
grade (as either calcined natural phosphorites or bone dust) is used
as a slow release fertilizer for acidic soils [36].
(PO
)
3
4
2
1.3.7 α-TCP
α-tricalcium phosphate (α-Ca
; the chemically correct
names are calcium orthophosphate tribasic alpha or tricalcium
bis(orthophosphate) alpha) is usually prepared from β-TCP at
heating above ~1125°C [250] and it might be considered as a high
temperature phase of β-TCP. However, at the turn of the millennium,
the previously forgotten data that the presence of silicates stabilized
α-TCP at lower temperatures of 800-1000°C [251] have been
(PO
)
3
4
2
Search WWH ::
Custom Search