The enhancement of glass ionomer cement mechanical strength through the incorporation of fluorhydroxyapatite nanocrystals

Abstract

Recent developments of glass ionomer cement (GIC) have made it to become an excellent dental restorative material, nevertheless, its mechanical properties still need to be improved. The mechanical strength of glass ionomer cement could be enhanced through the addition of fluorhydroxyapatite nanocrystal, one of the minerals that compose dental hard tissues and therefore have great biocompatibility. This study aims to evaluate the effect of different amounts of fluorhydroxyapatite nanocrystals with different degrees of fluoridation incorporation to glass ionomer cement mechanical strength. Fluorhydroxyapatite nanocrystals with 0 to ∼95% fluoridation degrees were synthesized through a microwave-assisted precipitation method. The crystal phase, functional groups, surface morphology, and fluoridation degrees of the synthesized powder were determined through X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR) Spectroscopy, Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray (EDX) Spectroscopy. Thereafter, synthesized fluorhydroxyapatite powder was added to commercial glass ionomer cement (Fuji IX, GC Gold Label) with an amount of 5 wt%, 7.5 wt%, and 10 wt%. The glass ionomer cement which did not undergo fluorhydroxyapatite addition was used as the control group. The microhardness of the cement which has been conditioned for 24 hours in distilled water were evaluated with Vickers Microhardness Tester. Characterization methods revealed that the synthesized powder was nano-sized fluorhydroxyapatite with different degrees of fluoridation. The microhardness of the modified cement after being conditioned for 24 hours exhibited higher values (55-115 HV) compared to the control group (48.94 HV). The results showed that the microhardness of the modified cement would increase to a certain amount of fluorhydroxyapatite addition, and then decreases with further addition. On the other hand, the difference in fluoridation degrees of fluorhydroxyapatite at the addition of the same mass percentage would not produce a significant difference in the microhardness among the modified cement.