[The effect of heat application on microhardness of glass ionomer cement and on pulp temperature].

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.

METHODS: Discs of EQUIA (GC Co. Japan) were examined for microhardness using Vickers indentations after heat application of 50 or 60°C for 30 or 60 seconds using light curing devices or a specific heating device, and compared to self setting GIG. The measurements were performed after 30, 60 minutes and after 5 days. Heat was applied to GIC occlusal restorations in deciduous and permanent teeth in vitro and the effect on pulp temperature was measured using a thermo-coupling device. The best microhardness results were observed using a specific heating device at 50°C 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 60°C caused the pulp temperature to rise with more than the accepted 5.5°C and may cause irreversible damage to the pulp. 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 50°C for 30 seconds in order not to cause irreversible damage to the pulp.