Characterisation of Calcium Aluminate Glass Ionomer Cement

Abstract

Background: Ceramir® Crown & Bridge is a recently developed luting agent based on the hybridisation between calcium aluminate cement (CAC) and glass-ionomer cement (GIC). This relatively new cement is claimed to be bioactive and friendly to the tooth than conventional GIC. However, there are relatively few published studies, and no characterisation of the cement was done independently. Therefore, it is believed that any new dental material should be characterised by different laboratory tests to elucidate the material’s setting reaction, composition and various properties. Objectives: To characterise setting reaction and apatite formation, determine the chemical composition, fluoride release and film thickness of commercial calcium aluminate-glass ionomer cement (CaAl-GIC). Method: Three dental cements were used for this study, Ceramir Crown & Bridge (Doxa Dental, Uppsala, Sweden), KetacCem Maxicap (3M ESPE, MN, USA) and White ProRoot MTA (Dentsply, Tulsa, OK, USA). Each cement type was prepared in triplicate, immersed in 10 ml Tris Buffer (TB) and incubated (37°C) for 1, 7 and 28 days. Cement powder and aged samples were characterised by MAS-NMR, ATR-FTIR and XRD. The chemical composition of CaAl-GIC was determined by using XRF. Solutions collected at each time point were analysed for pH, fluoride release and ICP-OES. The film thickness was measured according to the ISO: 9917-1. Result:This study showed that the hybrid CaAl-GIC is predominantly composed of CaAl. The chemical analysis showed that CaAl-GIC has low amount of silica, phosphorus and fluorine and higher in aluminium oxide and calcium oxide when compared to GIC. CaAl-GIC showed no apatite formation at 24 hours, 7 days and 28 days after immersion in TB. MAS-MAS-NMR and XRD results of CaAl-GIC showed crystalline phases of monocalcium aluminate (CaAl2O4) and demonstrated the presence of strontium fluoride. ATR-FTIR and MAS-NMR spectra of CaAl-GIC are characterised by the presence of AlO4 tetrahedra and AlO6 octahedra and the presence of the metastable phases CAH10 (monocalcium aluminate decahydrate) and C2AH8 (dicalcium aluminate octahydrate). Fluoride release is higher in GIC than CaAl-GIC. The pH values are gradually increased over time and reaching a mean value of 8.28 after 28 days. CaAl-GIC has a film thickness within the range set by the ISO standards to be less than the maximum value (25 μm). Conclusion: This study showed that the setting reaction of CaAl-GIC could be characterised as an overlapping two steps-controlled reactions which involve a combination of an initial acid-base reaction similar to that occurred in GIC and a main hydration reaction similar to that occurred in CAC. CaAl-GIC showed no apatite formation after immersion in TB at different time points. The hybrid CaAl-GIC is mainly composed of CAC which could be responsible for high pH and end-product properties. Further work is required to complete characterisation of CaAl-GIC to reveal potential expectations of the material when clinically applied.