Comparative evaluation of heat versus microwave irradiation on the microhardness of glass ionomer cements

Abstract

Objective: To compare the effects of conventional oven heat and microwave treatments on the surface microhardness of conventional glass ionomer cement (GIC). Materials and Methods: Thirty disc-shaped specimens (10 mm diameter × 4 mm thickness) were fabricated from self-cured conventional GIC (Cavex) and randomly divided into three groups (n=10). The control group received no heat treatment and was stored at room temperature for 24 hours. The oven group was subjected to 50°C in a convection oven for 15 minutes after a 24-hour setting. The microwave group was exposed to microwave radiation for 10 minutes after the identical setting. Surface microhardness was evaluated using a Vickers hardness tester (25g load, 5 seconds, five indentations per specimen). Statistical analysis included descriptive statistics, pairwise correlation, and post-hoc Tukey HSD testing. Results: Microwave-treated specimens showed the highest mean microhardness, closely approaching or slightly exceeding controls. Oven-treated specimens exhibited the lowest values. Significant differences were found between microwave and control groups (p<0.05), with high correlation. Microwave samples showed the greatest variability; controls showed an optimal balance of high mean values, consistency, and predictability. Conclusion: Microwave treatment can maintain GIC microhardness, but variability limits reliability; the conventional 24-hour setting remains safest and most predictable.