Antifungal, optical, and mechanical properties of polymethylmethacrylate material incorporated with silanized zinc oxide nanoparticles

Abstract

Background: Fungal infected denture, which is typically composed of polymethylmethacrylate (PMMA), is a common problem for a denture wearer, especially an elderly patient with limited manual dexterity. Therefore, increasing the antifungal effect of denture by incorporating surface modification nanoparticles into the PMMA, while retaining its mechanical properties, is of interest.

Aim of the study: This study aimed to evaluate antifungal, optical, and mechanical properties of heat-cured PMMA incorporated with different amounts of zinc oxide nanoparticles (ZnOnps) with or without methacryloxypropyltrimethoxysilane modification.

Materials and methods: Specimens made from heat-cured PMMA containing 1.25, 2.5, and 5% (w/w) nonsilanized (Nosi) or silanized (Si) ZnOnps were evaluated. Specimens without filler served as control. The fungal assay was performed placing a Candida albicans suspension on the PMMA surface for 2 h, then Sabouraud Dextrose Broth was added, and growth after 24 h was determined by counting colony forming units on agar plates. A spectrophotometer was used to measure the color in L* (brightness), a* (red-green), b* (yellow-blue) and opacity of the experimental groups. Flexural strength and flexural modulus were determined using a three-point bending test on universal testing machine after 37°C water storage for 48 h and 1 month.

Results: The antifungal, optical, and mechanical properties of the PMMA incorporated with ZnOnps changed depending on the amount. With the same amount of ZnOnps, the silanized groups demonstrated a greater reduction in C. albicans compared with the Nosi groups. The color difference (ΔE) and opacity of the Nosi groups were greater compared with the Si groups. The flexural strength of the Si groups, except for the 1.25% group, was significantly greater compared with the Nosi groups.

Conclusion: PMMA incorporated with Si ZnOnps, particularly with 2.5% Si ZnOnps, had a greater antifungal effect, less color differences, and opacity compared with Nosi ZnOnps, while retaining its mechanical properties.

Keywords: antifungal effect; mechanical properties; optical properties; silanized zinc oxide nanoparticles.

Figure 1

Mean and standard deviation of the growth of Candida albicans in each experi mental group. Note: Groups with the same letter (A–D) were not significantly different (P<0.05). Abbreviations: CFU, colony forming unit; Nosi, nonsilanized; Si, silanized.

Figure 2

Photograph of the experimental groups: (A) control, (B) 1.25Si, (C) 1.25Nosi, (D) 2.5Si, (E) 2.5Nosi, (F) 5Si, and (G) 5Nosi. Abbreviations: Nosi, nonsilanized; Si, silanized.

Figure 3

Representative SEM images of the fractured surface of specimen (35,000×): (A) control, (B) 5Si, and (C) 5Nosi. Note: The white arrows indicated the aggregated ZnOnps on the fractured surface of specimen. Abbreviations: SEM, scanning electron microscope; Si, silanized; Nosi, nonsilanized.

Figure 4

Representative Zn-mapping images of the surface of specimen using EDX on SEM (2,000×): (A) 5Si and (B) 5Nosi. Abbreviations: EDX, energy dispersive X-ray; SEM, scanning electron microscope; Si, silanized; Nosi, nonsilanized.