Mechanical properties of a silver nanoparticle modified glass-ionomer

Abstract

Objective

Silver nanoparticles (Ag-NPs) are well known for their antimicrobial effect; however, their use in restorative materials has been restricted in the past due to unacceptable colour properties. A neutral coloured Ag-NP suspension was developed and incorporated into a commercially-available glass ionomer at the University of Otago. This study aims to investigate the flexural strength of these specimens using a three-point bend test. It also aims to investigate the hardness and elastic moduli of these specimens using nano indentation.

Methods

The ISO protocol for determining three-point flexural strength of dental cements 9917-2:2010 was followed. Five groups of glass ionomer samples were prepared. The control group was Fuji IX GP (Group A), and the test groups were also Fuji IX GP samples with the liquid part modified by different concentrations of the Ag-NP suspension: 5µl 100% Ag-NP suspension added to the liquid (Group B), 5µl 100% Ag-NP suspension substituted into the liquid (Group C),10µl 50% Ag-NP suspension added to the liquid (Group D) and 10µl 50% Ag-NP suspension substituted into the liquid (Group E). Three-point flexural strength values were obtained for statistical analyses. A Weibull analyses was also performed. Samples were prepared in the same way for nanoindentation and tested at day-1 and then at day-7 to obtain the hardness and elastic moduli of the groups.

Results

Flexural strength values were compared between control and test groups using the non-parametric Kruskal-Wallis test with Dunn’s post-hoc analysis. No significant differences were noted in the post-hoc analysis. The hardness and elastic moduli at Day-1 and at Day-7 were also compared using one-way and two-way ANOVAs and Tukey’s multiple comparisons tests. Differences between the groups could be correlated to the variation in fluid content of the capsules.

Conclusions

This study highlights the correlation between the powder/liquid ratio in the glass-ionomer and its mechanical properties. The Ag-NP modification in some of the groups tested resulted in comparable mechanical properties to the unmodified commercial product. Incorporating the Ag-NPs directly into the glass-ionomer liquid is suggested for future investigations.