Biomedical Engineering Reference
In-Depth Information
ceramic has higher mechanical strength than cortical bone. Bioactive
ceramics are most frequently used as bone defect illers. They are
supplied in the forms of block, porous material, and granules [49].
The glass ceramic has good biocompatibility, bioactivity, and no
toxicity, making it useful as a biomaterial in artiicial bone and dental
implants.
The base components in most bioactive glasses and glass
ceramic made by traditional high-temperature melting, casting and
sintering are SiO
2
, Na
2
O, CaO, and P
2
O
5
. The irst and well studied
composition is 45S5 Bioglass, which contains 45% SiO
2
, 24.5% Na
2
O,
24.5% CaO, and 6% P
2
O
5
(in weight percent). The compositions and
some mechanical properties of several typical bioactive glasses are
given in Table 3.26.
Ta b l e 3
.
26
Composition (wt %) and mechanical properties of bioactive
glasses [20]
45S5
Bioglass
45S5
,
4F
Bioglass
45B15S5
Bioglass
52S4
.
6
Bioglass
55S4
.
3
Bioglass
Component
SiO
2
45
45
30
52
55
P
2
O
5
8
6
6
6
6
CaO
24.5
14.7
24.5
21
19.5
Na
2
O
24.5
24.5
24.5
21
19.5
CaF
2
—
9.8
—
—
—
B
2
O
3
—
—
15
—
—
Class
A
A
A
A
B
BS [MPa]
40-60 —
—
—
—
E
[GPa]
30-50 —
—
—
—
BS, Bending strength;
E
, Young's modulus.
A series of glasses in four component system with a constant
6 wt% P
2
O
5
were studied [49]. The compositional dependence of
the bioactive bonding-boundary for this system is shown in Fig. 3.5.
In the region A, the glasses are bioactive and bond to bone. Glasses
in region B behave as nearly inert materials and result in a ibrous
capsule at the implant-tissue interface. Glasses in the region C are
resorbed within 10-30 days in tissue. Compositions in region D are
not technically practical and have not been implanted.
The low strength of a monophase bioactive glass restricts its
clinical applications to non-load bearing situation. A way to attempt
to solve this problem is to prepare a glass-ceramic by a process
