Are RMGICs Capable to Form Apatite and Remineralise Like GICs?

Objectives: The objective was to study the ability of experimental RMGICs to re-mineralise and form apatite in artificial saliva (AS).
Methods: Three synthetic RMGICs with varying phosphorus content in glass (0.5P₂O₅, 0.75P₂O₅, 1P₂O₅) and commercial cement (Fuji II LC) were examined. Set cement disks (n=3) were immersed in AS for 2-weeks, 1-month, 3-months and 6-months. ³¹P Magic-Angle-Spinning-Nuclear-Magnetic-Resonance (³¹P MAS-NMR), Fourier-transform-infrared (FTIR), X-ray-diffraction (XRD) and Scanning-Electron-Microscopy with energy dispersive X-ray-spectroscopy (SEM/EDX) were used to determine the ability of these cements to form apatite.
Results: ³¹P MAS-NMR, FTIR, XRD of the home-made-compositions with low phosphorus displayed evidence of increasing apatite formation over time. On the contrary, the commercial composition showed no signs of apatite formation even up to 6-month immersion period. SEM images demonstrated a drastic change on the surface of the cement disks after immersion. Deposition of a calcium phosphate layer was observed, which was confirmed by the relative increase in phosphate (P) and calcium (Ca) concentration over the nominal concentration of aluminium (Al) and silicon (Si) with ageing of cements, as seen by EDX.
Conclusions: The results demonstrate that similar to GIC, using the same ionomer glass composition, RMGICs are capable of forming apatite on immersion in AS, with time.