Fabrication of an Al₂O₃– Free Glass Ionomer Cement

Introduction: Glass ionomer cements are commonly used in dentistry, however they can also be used as bone cements. Commercial glass ionomer bone cements are all based on an alumino-silicate glass. The release of Al³⁺ from the cement has been associated with poor bone mineralisation and neurotoxicity. Hurrell-Gillingham et al [1-3] have recently reported the formation of a GIC fabricated using an Fe₂O₃ based glass. These glasses however contained significant amounts of Al₂O₃ contamination. Objective: The aim of this research was to fabricate a truly Al₂O₃ -free glass and use it to fabricate GIC's. Method: Glasses with the molar composition of 4.5SiO₂.3Fe₂O₃.XP₂O₅.3CaO.2CaF₂ (X = 0 to 1.5) were fabricated using a conventional glass-processing route. Cements were prepared using standard ratio; 1 g of glass powder: 0.2 g of dried polyacrylic acid: 0.3 g of 10% tartaric acid solution. X-ray fluorescence (XRF) was used to determine the composition of the glasses. Setting and working times of the cements were determined using Gilmore needle indentation testing. Results: XRF revealed that in all glasses the Al₂O₃ content was <0.5 mol%. The presence of this small amount of contamination is believed to come from the raw materials used to batch the glass. It was possible to fabricate GIC's from all of the glasses in the series, however only one glass (X = 0.77) had working and setting times comparable to the commercial GI bone cement. Conclusion: Ionomer glasses may be prepared by entirely replacing Al₂O₃ with Fe₂O₃. Further work is required to characterise these true Al₂O₃-free glasses. References: [1] Hurrell-Gillingham et al, Key Eng. Mat. 2005, 284-286, pp 799-802, [2] Hurrell-Gillingham et al, J. Dent, in press, [3] Hurrell-Gillingham et al, BSDR 2004 #0129. This work was supported by the UK Medical Devices Faraday Partnership (EPSRC grant GR/S78254/01) and Corinthian Surgical.