Amorphous bioactive glasses such as 45S5 have been successfully used in bone‐filling therapy in non‐load bearing biomedical applications for decades. In this study, we challenge the predilection to amorphous over crystalline ceramics by investigating the effect of synthesis route on surface texture, in vitro dissolution, and mineral formation on powders produced by sol–gel and glass melt‐casting methods. Many reports have indicated bulk crystalline bioactive glass‐ceramics to be less bioactive than their amorphous counterparts as measured by the onset time for mineral formation. Bioactive glass 45S5 was synthesized using the sol–gel method followed by heat treatment to produce a semi‐crystalline structure and was compared against commercially available amorphous melt‐cast 45S5 powder. Gel‐derived samples were stabilized at 700°C making more than 80% of the structure crystalline. Dissolution of 45S5 glass‐ceramic in powder form(particle diameter 12 μm) was studied by in vitro immersion in simulated body fluid solution for various periods of time. The immersed powders were then analyzed through X‐ray diffraction (XRD), Scanning electron microscopy (SEM), energy dispersive X‐ray analysis (EDS), Differential scanning calorimetry (DSC), and thermogravimetric analysis (DSC/TGA), and Fourier transform infrared spectroscopy (FTIR) to determine the onset time for surface mineralization, and were compared with the melt‐cast powder as a control. The rates of dissolution and onset time for mineral formation were similar for the gel‐derived powder as compared with the melt‐cast control; it is proposed that the higher surface area of the sol–gel powder overcame the penalty usually associated with lower dissolution rates of crystalline materials, implicating surface texture as a much more important determinant of dissolution and mineralization behavior than mere crystallinity.

The outward flux of aluminum during the oxidation of four similar aluminaforming alloys is determined using two types of experiments. One is measurement of the total thickness of the oxide and the ratio of the thickness of the characteristic equiaxed layer to the total oxide thickness. The second is measurement of the new oxide formed along the grain boundaries of the oxide upon re-oxidation. The former provides information about the ratio of outward diffusion of aluminum to inward diffusion of oxygen during oxidation. The latter experiment directly quantifies the outward flux of aluminum as a function of oxide thickness. Both the outward aluminum flux and the ratio of inward to outward diffusional fluxes are found to vary with the minor concentrations of "reactive element" alloying additions. Specifically, Y in solution in the alloy is found to limit outward aluminum diffusion more than Zr in solution, with Y 2 O 3 limiting aluminum diffusion more than Zr, Y, and ZrO 2 .

Thermodynamic solution theories allow the prediction of chemical potentials in solutions of known composition. In cryobiology, such models are a critical component of many mathematical models that are used to simulate the biophysical processes occurring in cells and tissues during cryopreservation. A number of solution theories, both thermodynamically ideal and non-ideal, have been proposed for use with cryobiological solutions. In this work, we have evaluated two non-ideal solution theories for predicting water chemical potential (i.e. osmolality) in multi-solute solutions relevant to cryobiology: the Elliott et al. form of the multi-solute osmotic virial equation, and the Kleinhans and Mazur freezing point summation model. These two solution theories require fitting to only single-solute data, although they can make predictions in multi-solute solutions. The predictions of these non-ideal solution theories were compared to predictions made using ideal dilute assumptions and to available literature multi-solute experimental osmometric data. A single, consistent set of literature single-solute solution data was used to fit for the required solute-specific coefficients for each of the non-ideal models. Our results indicate that the two non-ideal solution theories have similar overall performance, and both give more accurate predictions than ideal models. These results can be used to select between the non-ideal models for a specific multi-solute solution, and the updated coefficients provided in this work can be used to make the desired predictions.

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Polishing the surface is recommended for a full-contour zirconia restoration because polished zirconia presents favorable wear behavior opposing natural teeth.