Biomedical Engineering Reference
In-Depth Information
or self-setting calcium phosphate cement for injectable/mouldable bone
substitutes. Different types of injectable/mouldable bone substitutes have been
developed:
a) injectable biomaterial without initial hardening, where BCP granules are
associated with a hydrosoluble polymer;
b) the association of MBCP and fi brin sealant,
c) the association of synthetic self hardening polymers and
d) new generation macroporous calcium phosphate cements.
The purpose of this chapter is to review the fundamental properties of
biphasic calcium phosphate bioceramics, their biological properties, the develop-
ment of new technologies for tissue engineering, and examples of clinical
applications.
4.2 INTRODUCTION
In 1920, Albee reported the fi rst successful application of a calcium phosphate
reagent for the repair of a bone defect in humans [1]. More than 50 years later,
clinical use of a “tricalcium phosphate” preparation in surgically-created peri-
odontal defects in animals was reported by Nery et al. [2] and the use of dense
hydroxyapatite HA as an immediate replacement for tooth root was reported by
Dennnissen [3]. Largely through the separate efforts of Jarcho, de Groot and
Aoki in the early 1980s [4-7], synthetic hydroxyapatite (HA) and
β
- tricalcium
phosphate (
-TCP), became commercially available as bone substitute materials
for dental and medical applications. The BCP concept has been widely developed
by Daculsi and Legeros since the 1990s [8-11].
Developing BCP ceramics and other related biomaterials for bone grafts re-
quired controlling the processes of bioceramic resorption and bone formation at
the expense of the biomaterial [12-15]. Synthetic bone graft materials are avail-
able as alternatives to autogeneous bone for repair, substitution or augmentation.
The BCP concept [10] is based on an optimum balance between the more
stable phase (HA) and the more soluble phase (
β
- TCP). BCP bioceramics are
soluble and gradually dissolve
in
vivo
, seeding new bone formation as it releases
calcium and phosphate ions into the biological medium. Commercial BCP
bioceramics consist of a mixture of hydroxyapatite (HA), Ca
10
(PO
4
)
6
(OH)
2
and beta - tricalcium phosphate (
β
β
- TCP), Ca
3
(PO
4
)
2
of varying HA/
β
- TCP ratios
(Table 4.1 ).
At the present time, commercial BCPs are sold in Europe, U.S., Brazil,
Japan, Korea, Taiwan and China as bone-graft or bone substitute materials for
orthopedic and dental applications under various trade marks. Currently, BCP
bioceramics are recommended for use as an alternative or additive to autoge-
neous bone for orthopedic and dental applications.
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