Effect of heat application on the mechanical behaviour of glass ionomer cements

The aim of this study was to examine the long-term effect of heat on the mechanical behaviour of conventional highly viscous glass ionomer cements. Besides, the effect of storage time was evaluated. Five cements (ChemFil Rock, Riva Self Cure, Fuji IX GP Fast, Equia and Ketac Molar Aplicap) were evaluated using three different preparation methods: no heat application, application of heat by means of a LED curing unit for 20 and 60 s. Four hundred fifty bar-shaped specimens were produced, maintained in distilled water at 37 A degrees C and tested after 1 week, 1 month and 3 months (n = 10). The Vickers hardness, indentation modulus and creep were measured. In addition, the amount and size of the glass fillers and voids were examined using a light and a scanning electron microscope. Fuji IX GP Fast showed the highest Vickers hardness, Ketac Molar Aplicap showed the highest indentation modulus and the best value of creep was measured for Riva Self Cure. Vickers hardness, modulus of elasticity and creep resistance increased most for ChemFil Rock and Equia up to 1-month storage. Heat application showed no effect on the mechanical behaviour of ChemFil Rock, Fuji IX GP Fast and Equia at all ageing time. The impact of storage duration was low. Considering the measured mechanical properties, there is no need of using heat when restoring teeth with glass ionomer cements.