Biomedical Engineering Reference
In-Depth Information
Brown and Chow [13-16] in the early 1980s. However, there is an
opinion [17] that self-setting calcium orthophosphate formulations
for orthopedic and dental restorative applications have first been
described in the early 1970s by Driskell et al. [18]. More to the point,
there are researchers, who worked with similar reactions even
earlier. Namely, in 1950, Kingery investigated chemical interactions
among oxides and/or hydroxides of various metals (including CaO)
with H
and discovered several self-hardening formulations
[19]; thus, he appears to be the first (see Chapter 8). Leaving aside
the priority topic, we further discuss the material subject, which
currently is known as
PO
3
4
(commonly referred
to as CPC), and, due to their suitability for repair, augmentation and
regeneration of bones, these biomaterials are also named as calcium
phosphate
calcium phosphate cements
cements (occasionally referred to as CPBC) [20]. In
order to stress the fact that these cements consist either entirely or
essentially from calcium
bone
phosphates, this review is limited to
consideration of calcium orthophosphate-based formulations only.
The readers interested in formulations based on other types of
calcium phosphates are requested to read the original publications
[21].
Due to a good bioresorbability, all self-setting calcium
orthophosphate formulations belong to the second generation of
bone-substituting biomaterials [22]. These formulations are blends
of amorphous and/or crystalline calcium orthophosphate powder(s)
with an aqueous solution, which might be distilled water, phosphate-
buffered saline (PBS), aqueous solutions of sodium orthophosphate
(~ 0.25 M), orthophosphoric acid, citric acid (~ 0.5 M) [23], sodium
silicate [24, 25], magnesium hydroorthophosphate [26], or even
the revised simulated body fluid (rSBF) [27]. After the calcium
orthophosphate powder(s) and the solution are mixed together, a
viscous and moldable paste is formed that sets to a firm mass within
a few minutes. When the paste becomes sufficiently stiff, it can be
placed into a defect as a substitute for the damaged part of bone,
where it hardens
ortho
within the operating theatre. The proportion
of solid to liquid or the powder-to-liquid (P/L) ratio is a very
important characteristic because it determines both bioresorbability
and rheological properties. As the paste is set and hardened at room
or body temperature, direct application in healing of bone defects
became a new and innovative treatment modality by the end of the
in situ
Search WWH ::
Custom Search