Effect of silver nanoparticles incorporation on microhardness of Heat-cure denture base resins

Background: Poly (Methyl methacrylic acid) based materials are widely used for the fabrication of removable complete and partial denture prosthesis. Regular cleansing of these dentures may abrade the surface due to an inherent lack of adequate surface hardness. This roughness may adhere food to the denture surface, making it dirty and further cause stomatitis. Recently, antimicrobial activity of denture base materials incorporated with silver nanoparticles was studied, that may logically prevent microbial growth on the denture. However, the effect of these nanoparticles on the mechanical properties, which provide longevity to the prosthesis, was not substantiated.  Aim: This study was designed to evaluate the effect of incorporating various concentrations of silver nanoparticles into heat-cure denture base resin materials, on their surface hardness.  Materials and methods: Silver nanoparticles were incorporated at various concentrations (0.5, 1.0, 2.0 and 5.0 wt%) into three different heat-cure denture base materials. A total of 150 rectangular-shaped specimens (62 x 10 x 2.5), which comprises 50 samples from each of the three heat-cure acrylic resins were made using the compression moulding technique. Ten specimens (n=10) were allocated for each concentration such as control, 0.5wt%, 1.0wt%, 2.0wt% and 5.0wt% concentrations of silver nanoparticles. The microhardness was evaluated using the Vickers micro-hardness tester. The data were subjected to One way ANOVA and Tukey HSD tests for statistical analyses. Results: Significant differences (p=0.000) were observed between the unmodified and modified denture base materials.  Conclusion: Silver nanoparticles can be considered as the favourable additives to increase the surface hardness of denture base materials.