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Mechanical Enhancement for Longevity of Glass Ionomer Cement Using Cellulose Nanocrystals: A Study on Microhardness
Kiran Manjunath1, Vinod Jathanna1, Kishore Ginjupalli2
1Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences Mangalore, Manipal Academy of Higher Education, Manipal, India, manipal.edu.
Background:
Glass ionomer cement (GIC) has found extensive application in the field of restorative dentistry due to its chemical adherence to tooth structure and fluoride releasing characteristics. Nevertheless, its clinical use in load bearing, posterior restorations is constrained by poor surface microhardness and wear resistance. Cellulose nanocrystals (CNCs) are bio-derived nanomaterials which have high bond strength making them potential reinforcing agents in dental cements.
Objective:
To evaluate the surface microhardness and wear resistance of GIC incorporated with CNCs at concentrations of 0.2%, 0.5%, and 1% in comparison to an unmodified control.
Methods:
An in vitro experimental study was carried out on four groups (n = 12 per group): control (unmodified GIC), G1 (GIC + 0.2% CNCs), G2 (GIC + 0.5% CNCs), and G3 (GIC + 1% CNCs). Standardized rectangular specimens were prepared. The surface microhardness was measured by the use of a Vickers hardness tester and the wear resistance was evaluated on a pin-on-disc wear testing apparatus.
Results:
The highest mean surface microhardness was seen in G3 (208.1 ± 0.56), followed by G2 (157.4 ± 0.32), G1 (133.3 ± 0.37), and the lowest measurements were seen in the control group (98.3 ± 0.32 Vickers hardness number [VHN]). Mean wear resistance was highest in the control group (48.3 ± 0.31), followed by G2 (30.2 ± 0.28), G1 (30.1 ± 0.17), and the lowest in G3 (16.9 ± 0.26 VHN). The differences among the groups were statistically significant (p < 0.001).
Conclusion:
Incorporation of CNCs significantly improved the surface microhardness of restorative GIC in a concentration-dependent manner. However, higher CNCs concentrations were associated with reduced wear resistance. Further long-term studies are needed to determine the optimal CNCs concentration for clinical applications.