Table 5.
Ion activity product (IAP; mean ± SD) and the thermodynamic stability* (ΔG° ; mean ± SD) of the solutions containing Ca and PO4 ions released from BTHM and ETHM ACP composites at different time intervals. Number of repetitive experiments in each group n=3.
| Composite | Immersion Time (mo) | IAP | ΔG° (kJ/mol) |
|---|---|---|---|
| 1 | 121. ±5 0.1 | 1.33 ±0.04 | |
| BTHM30 | 3 | 117.1 ± 0.3 | 0.00 ± 0.03 |
| 6 | 112.3 ± 0.1 | − (1.58 ± 0.03) | |
| 1 | 114.0 ± 0.1 | − (1.05 ± 0.04) | |
| BTHM35 | 3 | 111.5 ± 0.2 | − (1.83 ± 0.07) |
| 6 | 107.9 ± 0.4 | − (2.97 ± 0.12) | |
| 1 | 112.1 ± 0.3 | − (1.64 ± 0.09) | |
| BTHM40 | 3 | 110.7 ± 0.3 | − (2.09 ±0.10) |
| 6 | 106.3 ± 0.4 | − (3.48 ± 0.07) | |
| 1 | 117.4 ± 0.1 | 0.03 ± 0.06 | |
| ETHM30 | 3 | 113.3 ± 0.3 | − (1.27 ± 0.10) |
| 6 | 109.3 ± 0.3 | − (2.53 ± 0.10) | |
| 1 | 112.5 ± 0.4 | − (1.52 ± 0.13) | |
| ETHM35 | 3 | 111.1 ± 0.2 | − (1.96 ± 0.06) |
| 6 | 107.8 ± 0.3 | − (3.00 ± 0.09) | |
| 1 | 112.1 ± 0.4 | − (1.64 ± 0.12) | |
| ETHM40 | 3 | 110.1 ± 0.5 | − (2.28 ± 0.16) |
| 6 | 105.8 ± 0.8 | − (3.64 ± 0.26) | |
*
Negative ΔG° value indicates solution supersaturated with respect to stoichiometric hydroxyapatite, Ca10(OH)2(PO4)6. The thermodynamic solubility product of Ca10(OH)2(PO4)6 used in calculations was Ksp = 117.1.