Table 2. Comparative composition and structural parameters of inorganic phases of adult human calcified tissues. Due to the considerable variation found in biological samples, typical values are given in these cases26,32.
| Composition, wt% | Enamel | Dentine | Cementum | Bone | HA |
|---|---|---|---|---|---|
| Calcium[a] |
36.5 |
35.1 |
~35 |
34.8 |
39.6 |
| Phosphorus (as P)[a] |
17.7 |
16.9 |
~16 |
15.2 |
18.5 |
| Ca/P (molar ratio)[a] |
1.63 |
1.61 |
~1.65 |
1.71 |
1.67 |
| Sodium[a] |
0.5 |
0.6 |
[c] |
0.9 |
– |
| Magnesium[a] |
0.44 |
1.23 |
0.5–0.9 |
0.72 |
– |
| Potassium[a] |
0.08 |
0.05 |
[c] |
0.03 |
– |
| Carbonate (as CO32-)[b] |
3.5 |
5.6 |
[c] |
7.4 |
– |
| Fluoride[a] |
0.01 |
0.06 |
up to 0.9 |
0.03 |
– |
| Chloride[a] |
0.30 |
0.01 |
[c] |
0.13 |
– |
| Pyrophosphate (as P2O74-)[b] |
0.022 |
0.10 |
[c] |
0.07 |
– |
| Total inorganic[b] |
97 |
70 |
60 |
65 |
100 |
| Total organic[b] |
1.5 |
20 |
25 |
25 |
– |
| Water[b] |
1.5 |
10 |
15 |
10 |
– |
|
Crystallographic properties: Lattice parameters (± 0.003 Å) |
|
|
|
|
|
|
a-axis, Å |
9.441 |
9.421 |
[c] |
9.41 |
9.430 |
|
c-axis, Å |
6.880 |
6.887 |
[c] |
6.89 |
6.891 |
| Crystallinity index (HA = 100) |
70–75 |
33–37 |
~30 |
33–37 |
100 |
| Typical crystal sizes (nm)103–105 |
100 µm × 50 × 50 |
35 × 25 × 4 |
[c] |
50 × 25 × 4 |
200–600 |
| Ignition products (800°C) |
β-TCP + HA |
β-TCP+ HA |
β-TCP+ HA |
HA + CaO |
HA |
| Elastic modulus (GPa) |
80 |
23.8 ± 3.7 |
15.0 ± 3.6 |
0.34–13.8 |
10 |
| Tensile strength (MPa) | 10 | 100 | [c] | 150 | 100 |
[a] Ashed samples. [b] Unashed samples. [c] Numerical values were not found in the literature but they should be similar to those for dentine.