A long-term study on the setting reaction of glass ionomer cements by 27Al MAS-NMR spectroscopy

ObjectivesThe main objective is the characterization of the setting reaction in glass ionomer cements (GICs) based on experimental glasses using the 27Al magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy in order to understand the crosslinking process during the setting reaction.MethodsThree types of GICs which are based on fluoro-alumino-silicate glasses (LG125, ART10, and LG26Sr) were studied using 27Al MAS-NMR to monitor the setting reaction of the cements.ResultsThe result showed clearly the formation of six coordinate, aluminium Al(VI), that crosslink the carboxyl groups in the PAA. The deconvolution study was performed to quantify the amount of each Al species in the cements. The finding showed that composition of original glass has a substantial effect on the setting behavior of the cements.SignificanceOur data demonstrate that the setting reaction of GICs can be followed by 27Al MAS-NMR spectroscopy discovering the conversion of Al(IV) to Al(VI). Considerable amount of the five coordinate aluminium, Al(V), species was found in the cements aged up to one year. The presence of phosphorus has a strong influence on the setting reaction. The formation of Al–O–P species was postulated to be present in the cement.