Dental Composites with Magnesium Doped Zinc Oxide Nanoparticles Prevent Secondary Caries in the Alloxan-Induced Diabetic Model

Abstract

Antibacterial restorative materials against caries-causing bacteria are highly preferred among high-risk patients, such as the elderly, and patients with metabolic diseases such as diabetes. This study aimed to enhance the antibacterial potential of resin composite with Magnesium-doped Zinc oxide (Mg-doped ZnO) nanoparticles (NPs) and to look for their effectiveness in the alloxan-induced diabetic model. Hexagonal Mg-doped ZnO NPs (22.3 nm diameter) were synthesized by co-precipitation method and characterized through ultraviolet-visible (UV-Vis), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) analysis. The Mg-doped ZnO NPs (1, 2.5 and 5% w/w) were then evaluated for antibacterial activity using a closed system in vitro biofilm model. Significant enhancement in the antibacterial properties was observed in composites with 1% Mg-doped ZnO compared to composites with bare ZnO reinforced NPs (Streptococcus mutans, p = 0.0005; Enterococcus faecalis, p = 0.0074, Saliva microcosm, p < 0.0001; Diabetic Saliva microcosm, p < 0.0001). At 1−2.5% Mg-doped ZnO NPs concentration, compressive strength and biocompatibility of composites were not affected. The pH buffering effect was also achieved at these concentrations, hence not allowing optimal conditions for the anaerobic bacteria to grow. Furthermore, composites with Mg-doped ZnO prevented secondary caries formation in the secondary caries model of alloxan-induced diabetes. Therefore, Mg-doped ZnO NPs are highly recommended as an antibacterial agent for resin composites to avoid biofilm and subsequent secondary caries formation in high-risk patients.

Keywords: antibacterial; dental materials; nanomaterials; oral biofilm; secondary caries.

Figure 1

(a) UV-vis analysis, (b) FTIR analysis, and (c) XRD analysis of bare and Mg-doped ZnO NPs.

Figure 2

(a) SEM of Bare ZnO NPs, (b) SEM of Mg-doped ZnO, (c) EDX of Bare ZnO NPs, and (d) EDX of Mg-doped ZnO NPs.

Figure 3

Elemental mapping to confirm the uniform distribution of Mg-doped ZnO NPs in composite (2.5%) at 200 μm (a), surface morphology of reinforced composite, (b) distribution of Oxygen in reinforced composite, (c,d) distribution of Zinc in reinforced composite, (e) distribution of Magnesium in reinforced composite, and (f) overlapped distribution of O, Zn, and Mg.

Figure 4

Antibacterial effect of composites with bare and Mg-doped ZnO NPs against (a) S. mutans, (b) E. faecalis, (c) saliva-derived microcosm, and (d) diabetic microcosm. p-value < 0.05 is flagged with one star (*), while (**) means p-value < 0.01, (***) represents a p-value < 0.001 and (****) shows p value < 0.0001. ns (not significant) represents statistically insignificance.

Figure 5

Compressive strength of composites with bare and Mg-doped ZnO NPs at varying concentrations. p-value < 0.001 is flagged with three stars (***), while ns (not significant) represents statistically insignificance.

Figure 6

pH buffering effect of composites with bare and Mg-doped ZnO NPs at varying concentrations.

Figure 7

% Hemolysis of composites with bare and Mg-doped ZnO NPs at varying concentrations. p-value < 0.0001 is flagged with four stars (****), while ns (not significant) represents statistically insignificance.

Figure 8

(a) Mouth oral cavity, secondary caries assessment, red arrows showing (b) marginal caries adjacent to simple composite, (c) visual changes in the enamel around the composite with ZnO, and (d) sound tooth surface around the restoration composite with Mg-doped ZnO.

Figure 9

Secondary caries assessment in the diabetic rodent model.