Effects of Temperature on Fluoride Release and Recharging of Glass-ionomers

Objective: To evaluate the effects of the ambient temperature on the fluoride release and recharging of glass-ionomers (GICs). Methods: The materials used were a conventional GIC, Ketac-Cem Maxicap [KC] (3M); two high viscosity GICs, Ketac-Molar Aplicap [KM] (3M), and Fuji¢ù [F] (GC) and one resin-modified GIC, Fuji¢òLC [FLC] (GC). Five discs (15mm diameter, 1mm thickness) of each material were prepared and stored in 100% humidity for 24h before being lapped. Specimens were then stored in deionised water at 4°æ, 37°æ and 55°æ, fluoride release was measured at 1, 2, 3, 5, 7, 14, 28 days respectively using ion chromatography and the ion selective electrode. Three groups of specimens of each material was prepared as above and stored at 37°æ for 30 days. Then each group was either recharged at 4°æ, 37°æ or 55°æ in 250ppm sodium fluoride solution for 5mins. Fluoride release was recorded 2 days before and 2 days after the recharge. The mean fluoride recharge values (µg/cm2) at 4°æ, 37°æ and 55°æ were 3.82, 3.91 and 5.31 [KC]; 1.42, 1.91 and 2.51 [KM]; 1.79, 2.53 and 3.04 [F]; 2.63, 3.39 and 3.90 [FLC]. The results were analysed using ANOVA. Results: Over the whole test, fluoride release measured with the electrode was greater than with the chromatography. Fluoride release and recharge varied significantly (p<0.05) with temperature for all materials (p<0.05). Fluoride release and recharge at 55°æ for all materials, was greater than at 37°æ, and at 4°æ. Conclusion: The fluoride release and recharge of GICs are affected by the ambient temperature. This may indicative of a 'smart' behaviour. Fluoride treatment of GICs at a high temperature is clinically recommended to improve their recharging ability.