Modification of glass-ionomer cements with synthesized hydroxyapatite and fluorapatite nanoparticles

Objectives: The objective of this study was to evaluate the addition of synthesized hydroxyapatite (HA) and fluorapatite (FA) nanoparticles to a conventional glass-ionomer cement (GIC) on the mechanical properties, while preserving their unique clinical properties.
Methods: HA and FA were synthesized using wet-chemical precipitation method. The obtained nanoparticles were characterized with X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). HA and FA were incorporated into the powder component of cement at 5% and 8 wt%. Compressive strength (CS) and diametral tensile strength (DTA) before and after 1, 7 and 28 days storing in distilled water were evaluated. Surface microhardness after 1 and 7 days storing in distilled water was determined using Vickers microhardness tester. Setting and working time was measured as specified in the ASTM standard. The surface morphology of the modified GICs was examined using SEM imaging.
Results: The morphology of the synthesized HA and FA nanoparticles was hexagonal and the average size of them were about 25 nm and 30 nm, respectively. The mechanical results of the modified GICs showed that addition of HA and FA (5 and 8 wt%) into the glass ionomer cement after 7 days storing in distilled water exhibited statistically higher CS about 107-113.6 MPa and 111-117.8 MPa, respectively, also, higher DTS 13-16 MPa and 14-19 MPa, respectively. The hardness of the glass ionomers containing HA and FA nanoparticles (5 wt%) increased by 2.21 % and 11.77%, respectively. In addition, working time and setting time by adding the 5% nanoparticles were reduced about 8.5% and 13.23 % for HA and 10.63% and 19.11 % for FA, respectively.
Conclusions: It was concluded that glass ionomer cements containing HA and FA are promising restorative dental materials with improved mechanical properties.