Turning Waste into Strength: Mechanical Evaluation of Glass Ionomer Cement Reinforced with Eggshell Powder

Background: Glass Ionomer Cement (GIC) is a widely used restorative material owing to its chemical adhesion to tooth structure, fluoride release, and biocompatibility. However, its limited mechanical strength restricts its application in stress-bearing areas. Chicken eggshell powder (CESP), a natural biowaste rich in calcium carbonate, has shown potential to enhance mechanical properties of dental materials. This study aims to evaluate the effect of incorporating 5% and 7% CESP by weight into GIC on its compressive strength and surface hardness.  Methods: An in-vitro study was conducted with 45 samples divided into three groups: Group 1 (control – GIC without CESP), Group 2 (GIC with 5% CESP), and Group 3 (GIC with 7% CESP). Eggshells were cleaned, powdered, and calcined at 500°C to obtain CESP. The specimens were prepared in standardized acrylic blocks and tested after 24 hours of incubation at 37°C. Compressive strength was measured using a universal testing machine, and surface hardness was evaluated using a Vickers microhardness tester.  Results: Group 2 showed significantly higher compressive strength than Groups 1 and 3, while Group 3 exhibited the highest surface hardness. Statistical analysis revealed highly significant differences (p < 0.001).  Conclusion: Incorporation of 5% CESP improves compressive strength, while 7% enhances surface hardness, making CESP a promising biofiller for reinforcing GIC.