Biomedical Engineering Reference
In-Depth Information
1.4
Ba
2
+
1.3
1.2
Pb
2
+
Sr
2
+
1.1
1.0
Ca
2
+
Cd
2
+
0.9
0.8
Fe
2
+
Co
2
+
Zn
2
+
Cu
2
+
Mg
2
+
0.7
Ni
9
+
Mn
2
+
Fe
3
+
Mn
3
+
Co
3
+
Cr
3
+
0.6
Al
3
+
0.5
0
No
inhibition
1
2
3
4
5
Moderate
inhibition
Severe
inhibition
Hydroxyapatite formation
Figure 6.6
Schematic showing the inhibitory effects of metal ions on HCA forma-
tion on borate glasses.
on concentration. One theory behind the HCA inhibition is that the
addition of small ions to the HCA structure acts as road blocks for the
formation of the next unit cell, essentially stopping HCA or other calcium
phosphate formation [9]. The formation of calcite can be explained by
calcium salt solubility. Calcite has a solubility limit just above HCA [18],
but, if calcium phosphate phases cannot form, then any free calcium in
a carbonated solution like body fluids will crystallize to the calcite phase
of calcium carbonate.
6.5 APPLICATIONS OF BIOACTIVE BORATE GLASSES
IN ORTHOPEDICS AND DENTAL REGENERATION
Silicate-based bioactive glasses have been used in treating bone defects for
over 20 years [8]. There are several articles in the literature describing the
need for silica to stimulate gene expression with bone grafting materials
[19]. Some of the work that is shown here will challenge that theory,
