The Effect of Heat Application on Microhardness of Glass Ionomer Cement and on Pulp Temperature-What to Use in the Clinic

Abstract

Abstract Objectives: To examine the effect of energy application on microhardness of glass-ionomer cement (GIC), and the effect of the temperature applied on pulp temperature, in vitro and in vivo. Methods: Discs of EQUIA (GC Co. Japan) were examined for microhardness using Vickers indentations after heat application of 50 or 60oC for 30 or 60 seconds using light curing devices or a specific heating device, and compared to self setting GIC. The measurements were performed after 30, 60 minutes and after 5 days. Heat was applied to GIC occlusal restorations in deciduous and permanent teeth both in vitro and in vivo and the effect on pulp temperature was measured using a thermo-coupling device. Results: The best microhardness results were observed using a specific heating device at 50oC for 30 or 60 seconds, and the differences to self setting material after 60 minutes were statistically significant. After 5 days the differences in microhardness were non-significant. Temperature of 60oC caused the pulp temperature to rise with more than the accepted 5.5oC and may cause irreversible damage to the pulp. Similar pulpal temperature changes were observed in vitro and in vivo in deciduous and permanent teeth. Significance: The application of heat energy to GIC using a heating device improved the surface microhardness significantly during the first 60 minutes. The temperature to be used is around 50oC for 30 or 60 seconds in order not to cause irreversible damage to the pulp.