Thermal analysis of contemporary glass-ionomer restorative materials

The thermal characteristics of four conventional glass-ionomer cement (GIC) dental restorative products as well as five resin-modified glass-ionomer (RMGI) materials over 1-year of storage were investigated. All materials were prepared following manufacturer's recommendations and placed into 40 μL aluminum differential scanning calorimeter (DSC) crucibles. Samples (n = 5) were stored at 37 C and 98 ± 2 % humidity until their appointed time of evaluation at which they were first subjected to specific heat analysis using DSC over 20-60 C that was immediately followed by a 37-600 C thermal scan at 10 C min ^-1. Samples were evaluated immediately after preparation, at 24 h, 1 week, 1 month, as well as at 3, 6, 9, and 12 months. Mean thermal results were compared with analysis of variance and Scheffe post-hoc testing (p = 0.05). All materials absorbed water during storage. Conventional GIC materials demonstrated increased polyalkenoate polymer maturity over the 12-month storage. The paste-paste RMGI materials, absorbed more water during storage and had increased specific heat values compared to powder-liquid RMGI materials. Of the RMGI materials investigated, only two materials demonstrated evidence of a continuing polyalkenoate matrix maturity that was within the limitations of the technology used, indicating the resin component in some newer formulations of RMGI restorative materials may severely limit the polyalkenoate reaction.