Assessment of the Microhardness of Three Different Glass Ionomer Cements After Microhydroxyapatite Incorporation: An In Vitro Study

Aim The study aimed to evaluate the impact of incorporating microhydroxyapatite on the microhardness of three different types of glass ionomer cement. Methodology A total of 120 disc-shaped specimens (7 mm in diameter and 3 mm in height) were prepared for the study, divided into three groups, each containing four subgroups of 10 samples. The materials tested included Zirconomer, conventional glass ionomer cement (CGIC), and resin-modified glass ionomer cement (RMGIC), with the addition of microhydroxyapatite in varying concentrations of 0, 5, 15, and 25 wt%. All specimens were stored in deionized water at 37ºC for 24 hours before being subjected to the Vickers microhardness test. Statistical analysis was performed using one-way ANOVA and Tukey's post hoc honest significance test (HSD) test, with a significance level set at p<0.05. Results The addition of 5 and 15 wt% microhydroxyapatite to Zirconomer and RMGIC significantly increased microhardness (p<0.001). The highest Vickers hardness number (VHN) was observed in the RMGIC group with 5 wt% of microhydroxyapatite. However, the RMGIC group with 25 wt% microhydroxyapatite showed a lower VHN compared to the control group (without hydroxyapatite) (p<0.001). Conclusion The incorporation of 5 and 15 wt% microhydroxyapatite enhanced the microhardness of CGIC, RMGIC, and Zirconomer. However, adding 25 wt% of microhydroxyapatite to RMGIC resulted in a reduction in hardness compared to the control group without microhydroxyapatite.