Biomedical Engineering Reference
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found when a paste is prepared using spherical powder. Besides, it
should be noted that the paste could become fluid with less amount
of liquid phase since no captured liquid exists in the case of spherical
powder [268].
Figure 5.3
A schematic representation of the experimental setup used to
quantify the injectability of the calcium phosphate cements.
Reprinted from Ref. [267] with permission.
Unfortunately, when a cement paste, which is a biphasic mixture
of a finely divided ceramic (powder, granules) and a liquid, is
submitted to a pressure gradient, the liquid may flow faster than
the solid, resulting in local changes of the paste composition.
Specifically, the paste present in the region of the highest pressure
(e.g., close to the plunger of a syringe) may become so depleted in
liquid that the biphasic mixture in this zone is not longer a paste
but a wet powder [263, 265]. Contrarily, the paste in the zone of the
lowest pressure (e.g., at the cannula tip) is enriched in liquid. Since
these effects are dynamic, the size of the zone depleted in liquid (wet
powder) increases during injection, eventually reaching the tip of
the injection device and plugging it. The phenomenon, in which the
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