Biomedical Engineering Reference
In-Depth Information
5.10
Conclusions
Thus, among the diverse range of bone replacing biomaterials,
self-setting calcium orthophosphate formulations undoubtedly
represent a distinct group because they are relatively simple
materials formed by combining a calcium orthophosphate mixture
with an aqueous solution. However, they symbolize an important
breakthrough in the field of bone-repair biomaterials, since they
offer the possibility of obtaining thermally unstable calcium
orthophosphates in a monolithic form at room or body temperature
by means of a cementation reaction. This particular fabrication
technique implies that the self-setting formulations are moldable
and therefore can adapt easily to the bone cavity providing a good
fixation and the optimum tissue-biomaterial contact, necessary
for stimulating bone ingrowth into them and their subsequent
osteotransduction [29].
Unfortunately, the perfect grafting material does not exist.
The self-setting calcium orthophosphate formulations are not an
exception to this statement. While possessing excellent biological
properties (osteoconduction and, occasionally, osteoinduction),
adequate setting time, excellent moldability and the capability to
deliver different bone-enhancing proteins/antibiotics at a local level,
unfortunately, the material lacks adequate mechanical properties
for applications other than non-loaded surgical sites (see Table 5.4
for other details). Nevertheless, even in its present state, the self-
setting calcium orthophosphate formulations appear to be suitable
for a number of applications. They can be injected into osteoporotic
bone to reinforce it or can be used to make granules and blocks
out of low-temperature calcium orthophosphates. Several types
of the self-setting formulations are now on the market (Tables
5.1 and 5.2), while scaffolds made of low-temperature calcium
orthophosphates are being tested. The use of slightly different
chemical compositions and various dopants affects both the setting
time and tensile strength that enables further improvements. In
addition, new trials are conducted with the reinforced formulations
and concretes, which represent additional attempts to improve the
existing products.
Search WWH ::
Custom Search