Comparative Assessment of the Shear Bond Strength of Green Synthetized Titanium Dioxide, Hydroxyapatite and Chitosan Nanoparticles Integrated in Orthodontic Adhesive and Evaluation of Antibacterial Ability, an In-vitro and Laboratory Study

Recently, nanoparticles have raised interest due to their antibacterial characteristics when added to composite adhesives, as the impact of the addition of nanoparticles on shear bond strength is not widely investigated.

The in Vitro and laboratory Study assessed the antibacterial ability and the shear bond strength (SBS) of greenly synthesized titanium dioxide nanoparticles bonded with orthodontic adhesive against those bonded to chitosan and hydroxyapatite.

The green titanium dioxide nanoparticles were prepared from Salvadora persica. Titanium dioxide nanoparticles were recorded via Fourier transform infrared spectroscopy analysis, the crystal appearance and morphology of titanium dioxide nanoparticles were investigated by UV–Visible reflectance spectrum, and the surface morphology was visualized using electron microscopy, and determination of titanium dioxide nanoparticles homogeneity and elemental distribution was achieved by energy dispersive X-ray spectrometry. An ex vivo study was performed using forty healthy extracted human premolars and randomly partitioned into four groups. The first group included brackets bonded with orthodontic adhesive (what brand, city, country) without nanoparticles; the second, third, and fourth groups contained titanium dioxide nanoparticles, chitosan nanoparticles alone, and chitosan with hydroxyapatite nanoparticles, respectively. SBS and the adhesive remnant index (ARI) scores were recorded. Measurement of SBS (MPa) of the different groups’ samples was performed 24 hours after preparation using a universal testing machine, and the adhesive remnant index was defined using a light stereomicroscope (Nikon SM2-10, Japan) at ×10 magnification. The prepared titanium dioxide nanoparticles were assessed for their antibacterial activity versus pathogenic Gram positive and negative bacterial species through disc diffusion assay. The SBS data were analyzed using debonding force, while the antibacterial assays were analyzed using SPSS 21 software via one-way ANOVA.

The characteristic analysis provided the elemental structure of the prepared titanium dioxide nanoparticles in addition to metal crystallization, textural features, and functional bonds. Based on the extracted data, the control group revealed higher mean SBS (8.54 ± 0.76) in parallel to the three groups containing nanoparticles incorporated composites. The group comprising titanium dioxide nanoparticles exhibited the nearest value to the control group (8.38 ± 0.78) and higher to that of the other two groups, chitosan and chitosan and hydroxyapatite, (7.92±0.86) and (7.48 ± 0.46) respectively. However, according to the One Way ANOVA test, the SBS values were not significantly different across all four studied groups (p= 0.379). The ARI score of 1 was the most prevalent among the four groups as determined in 18 teeth at 45%, with no significant difference between bracket groups (p=0.171). The minimum bactericidal concentrations of 5 g/mL were 1x10³ and 1x10⁵ against Escherichia coli O25: K11 and Staphylococcus intermedius.

The results of our study, as well as the ex-vivo and in-vitro findings, verified that incorporating titanium dioxide nanoparticles into an orthodontic adhesive enhanced its antibacterial impacts without adversely affecting its SBS for clinical usage.