Moheet, Imran Alam
(2020)
Characterization physico-mechanical and chemical properties of nano-hydroxyapatite-silica added glass ionomer cement.
Masters thesis, Universiti Sains Malaysia.
Abstract
The aim of this study was to synthesize and characterize different nanohydroxyapatite-
silica (nano-HA-SiO2) particles with various silica concentrations and to
investigate the effects of adding nano-HA-SiO2 to the conventional glass ionomer cement
(Fuji IX GC). Nano-HA-SiO2 was synthesized using one-pot sol-gel technique, which was
then characterized using fourier transform infrared spectroscopy (FTIR), x-ray diffraction
(XRD), scanning electron microscope (SEM) and transmission electron microscope
(TEM). Further investigations were carried out on nano-HA-SiO2 added glass ionomer
cement (nano-HA-SiO2-GIC) to compare their mechanical (surface hardness, compressive
strength, flexural strength, and shear bond strength), chemical (fluoride ion release,
solubility and ion-exchange) and physical properties (colour stability, surface roughness,
sorption and micro-leakage) in relation to conventional glass ionomer cement (cGIC). It
was found that nano-powder consisted of a mixture of spherical silica particles (~50 nm)
and elongated hydroxyapatite particles in the range between 100-200 nm. Hardness,
compressive strength, and flexural strength of nano-HA-35SiO2-GIC was statistically
higher than that of nano-HA–21SiO2–GIC, nano-HA-11SiO2-GIC. The highest value for
Vickers hardness (64.77 6.18), compressive strength (143.42 13.94 MPa) and flexural
strength (17.68 1.81 MPa) were recorded by addition of 10% nano-HA-35SiO2 to GIC,
leading to an increase of ∼36 %, ∼19.7 % and ∼53.34 % in surface hardness, compressive
strength and flexural strength respectively as compared to conventional glass ionomer
cement (cGIC). 10% nano-HA–35SiO2-GIC also demonstrated higher shear bond strength
(∼17.54 % increase) as compared to cGIC. Nano-HA-35SiO2-GIC was more colour stable
material as it showed “slight - noticeable” change in colour as compared to cGIC that
displayed “noticeable to appreciable” change after 28 days of immersion in distilled water.
Nano-HA-35SiO2-GIC showed significantly lower surface roughness (0.13 ± 0.01 μm) as
compared to cGIC (0.16 ± 0.03 μm) on day 1. Additionally, nano-HA-35SiO2-GIC
showed highly significant difference (p=0.002) in amount of mean F+ release for all the
time intervals as compared to cGIC (p ≤ 0.05). In addition, Nano-HA-35SiO2-GIC
recorded higher values for both solubility and sorption (83.7 ± 19.04 μgmm-3 and 50.92 ±
12 μgmm-3) as compared to cGIC (56.65 ± 10.15 μgmm-3 and 42.64 ± 6.74 μgmm-3). It
also exhibited lower micro-leakage both at occlusal and gingival margins (0.2 ± 0.42 and
2.7 ± 0.67) as compared to cGIC (0.5 ± 0.71 and 3 ± 0.00). A greater ion-exchange was
displayed by nano-HA-35SiO2-GIC at ion-exchange layer (IEL) as well as the tooth
structure (enamel and dentin) as compared to cGIC. The addition of nano-HA-silica to
conventional GIC significantly enhanced the mechanical, physical and chemical
properties except sol-sorption properties of the material. Based on the findings of the
current study, nano-HA-SiO2-GIC can be suggested as a potential dental restorative
material.
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