The effect of phosphate, fluorine, and soda content of the glass on the mechanical properties of the glass ionomer (polyalkenoate) cements

Abstract

The main objective was to study the effect of reducing the phosphate content of the glass structures and the mechanical properties of the resultant cements. The effect of fluorine and soda content on the fluoride release was also investigated.A fluoro-aluminosilicate glass and its modified glass compositions were studied. The structures of the glasses were determined using X-ray diffraction (XRD), 27Al, 19F, and 31P Magic Angle Spinning (MAS) NMR, and DSC. The mechanical properties and the fluoride release of the cements were also measured.Phosphorous forms Al-O-P linkages in the glass. The formation of Al-O-P groups inhibits the degradation of the Si-O-Al bond in the Si-O-Al-O-PO33− group. Reducing the phosphate content decreases the proportion of Al-O-P bonds, with a concomitant change in the mechanical properties. The fluoride release kinetics was observed to be different, but there was no significant difference in the total amount of the fluoride released at 56days.The mechanical properties of the glass ionomer cements (GICs) increased by a simple reduction of the phosphate content. The compressive strengths of the cements were twice the ISO standard and were higher than the commercially available cements. Therefore, this study could be a basis to improve the properties of GICs.