Effects of magnesium content on the physical, chemical and degradation properties in a MgO−CaO−Na2O−P2O5 glass system

This paper presents the structural characterisation and degradation behavior of the glass system 20Na2O–(30−X)CaO–XMgO–50P2O5 (X=0, 5, 10, 15, 20, 25 and 30 mol%) whereinmagnesiumoxide is introduced as a partial calciumoxidesubstitute. This system is of interest fromthe viewpoint of investigating the subtle effects on structureand degradation that arise from the substitution of divalent ions (Mg2+ for Ca2+) in these glass systems. Studiessuch as differential thermal analysis (DTA), Fourier transform infrared (FTIR) spectroscopy and 31P nuclearmagneticresonance (NMR) reveal little change in the glass structure. However, degradation and ion release measurementsfor glass discs immersed in deionised water at 37 °C over a 21 day period highlight an inverse exponentialeffect between glass degradation rate and MgO content. Thus, the investigated glass systems provide interestinginsights into the effects of parameters such as ionic radius, atomic weight and bond length on the glass properties.From an applications perspective, these glasses offer a selective range of degradation rates from highly degradableto relatively stable systems and can potentially serve as vehicles for the delivery of magnesiumions in the clinicalrealm.