Boron Nitride Nanotubes as Filler for Resin-Based Dental Sealants

Abstract

The aim of this study was to evaluate the influence of boron-nitride nanotubes (BNNTs) on the properties of resin-based light-curing dental sealants (RBSs) when incorporated at different concentration. RBSs were formulated using methacrylate monomers (90 wt.% TEGDMA, 10 wt.% Bis-GMA). BNNTs were added to the resin blend at 0.1 wt.% and 0.2 wt.%. A Control group without filler was also designed. Degree of conversion, ultimate tensile strength, contact angle, surface free energy, surface roughness and color of the RBSs were evaluated for the tested materials. Their cytotoxicity and mineral deposition ability (Bioactivity) were also assessed. A suitable degree of conversion, no effect in mechanical properties and no cytotoxic effect was observed for the experimental materials. Moreover, the surface free energy and the surface roughness decreased with the addition of BNNTs. While the color analysis showed no difference between specimens containing BNNTs and the control group. Mineral deposition occurred in all specimens containing BNNTs after 7d. In conclusion, the incorporation of BNNTs may provide bioactivity to resin-based dental sealants and reduce their surface free energy.

Figure 1

Cell viability (%) of experimental resin-based sealants against keratinocytes (Fig. 2A) and pulp fibroblasts (Fig. 2B) cell lines. The uppercase letters indicate significant statistical difference within each cell type.

Figure 2

Raman analysis of mineral deposition after 7, 14 and 21 days after immersion of samples in artificial saliva. (A) Representative image of the analyzed area (500 µm × 500 µm). (B) Representative Raman spectrum showing the PO₄³⁻ peak (960 cm⁻¹). (C) Images obtained after the integration of the absorbance peak of 960 cm⁻¹ on micro Raman spectrometer. The increase in phosphate peak (960 cm⁻¹) is represented by the different colors in the images increasing from blue to orange as shown in the legend. Mineral deposits were found after 7 days of immersion in artificial saliva for the groups containing BNNTs. Increase of mineral deposition was found on the surface of experimental sealants containing higher amount of BNNTs concentration.

Figure 3

SEM images of the surface of specimens after immersion in artificial saliva for 28 days. Mineral deposition was found over the surface of specimens containing BNNTs.

Figure 4

Representative FTIR spectrum with the peaks used to measure the degree of conversion. The C=O and C=C peaks were used to the calculation according to the formula.