Measurement of ion concentrations for bioactive glass dissolution. (A) Ion concentration and (B) pH measurements [release rate: 6.4 ± 0.9 × 10−7 moles OH– L−1 h−½.]] for calcium, total phosphate, silicon, and magnesium released from 6P53-b particulates in α-MEM. (C) Ion concentration and (D) pH measurements [(8.2 ± 0.4 × 10−7 moles OH– L−1 h2−½.)] for calcium, total phosphate, silicon, and magnesium released from 45S5 particulates in α-MEM. (E) Calculations of the degree of saturation (DS) for 45S5 and 6P53-b ion concentrations and (F) 45S5 and 6P53-b GCM and control GCM during in vitro cell culture studies (concentrations given in A and C). For DS 5 14, the in vitro environment is considered super-saturated and the migration of calcium, phosphate, and hydroxyl ions from the liquid phase to the surface is likely. At DS = 12, the solution is supersaturated, however, heterogeneous nucleation is more likely to occur. For DS < 0, the solution is considered stable and these ions remain soluble.