Advanced Dentistry Biomaterials Containing Graphene Oxide

Abstract

The aim of this study was to obtain three experimental resin-based cements containing GO and HA-Ag for posterior restorations. The samples (S0, S1, and S2) shared the same polymer matrix (BisGMA, TEGDMA) and powder mixture (bioglass (La₂O₃ and Sr-Zr), quartz, GO, and HA-Ag), with different percentages of graphene oxide (0%, 0.1%, 0.2% GO) and silver-doped hydroxyapatite (10%, 9.9%, 9.8% HA-Ag). The physical-chemical properties (water absorption, degree of conversion), mechanical properties (DTS, CS, FS), structural properties (SEM, AFM), and antibacterial properties (Staphylococcus aureus, Enterococcus faecalis, Streptococcus mutans, Porphyromonas gingivalis, and Escherichia coli) were investigated. The results showed that the mechanical properties, except for the diametral tensile test, increased with the rise in the %GO. After 28 days, water absorption increased with the rise in the %GO. The surface structure of the samples did not show major changes after water absorption for 28 days. The antibacterial effects varied depending on the samples and bacterial strains tested. After increasing the %GO and decreasing the %HA-Ag, we observed a more pronounced antibacterial effect. The presence of GO, even in very small percentages, improved the properties of the tested experimental cements.

Keywords: antibacterial properties; cement; graphene oxide; hydroxyapatite; posterior restoration.

Figure 1

The bacterial strains studied and the samples (S0, S1, and S2) tested (Sa—Staphylococcus aureus, Ec—Escherichia coli, Ef—Enterococcus faecalis, Pg—Porphyromonas gingivalis, Sm—Streptococcus mutans).

Figure 2

The degree of conversion of the liquid sample and of the cement samples immediately cured and 24 h after polymerization.

Figure 3

Stress–strain curves for the mechanical tests.

Figure 4

Water absorption of sample S0 (without GO) and samples S1 and S2 (with 0.1% and 2% GO, respectively) after 1, 2, 3, 7, 10, 14, 21, and 28 days.

Figure 5

SEM images on the surface of samples S0 (a,d), S1 (b,e), and S2 (c,f) before the water absorption test (a–c) and after 28 days of storage in water (d–f).

Figure 6

AFM images of the samples’ fine microstructures before liquid immersion: (a) S0, (b) S1, (c) S2 and after liquid immersion for 28 days: (d) S0, (e) S1, and (f) S2.

Figure 7

AFM images of the sample’s nanostructure before liquid immersion: (a) S0, (b) S1, (c) S2 and after liquid immersion for 28 days: (d) S0, (e) S1, (f) S2.

Figure 8

Surface roughness variation for the (a) fine microstructure and (b) nanostructure.

Figure 9

Antibacterial activity of the cement samples (S0, S1, S2), after 48 h of incubation against Sa—Staphylococcus aureus, Ec—Escherichia coli, Ef—Enterococcus faecalis, Pg—Porphyromonas gingivalis, Sm—Streptococcus mutans.