Assessment of the Biocompatibility and Biomechanical Characteristics of Experimental Nickel Titanium Wires

Abstract

The aim of this study was to compare the mechanical and biological properties of an experimental NiTi archwire coated with nanocarbon tubes, a mechanically-treated NiTi archwire and an as-received NiTi archwire. To test this, NiTi wires from American Orthodontics (AO) with a cross-section of 0.019” x 0.025” were used for all the tests, except for the friction test where 0.017” x 0.025” wires were used. The three groups were compared for hardness, roughness, friction, yield strength, load deflection and modulus of elasticity, as well as biocompatibility. <br /> The first group was treated mechanically with the addition of carbon nanotubes (CNTs). The second group was only treated mechanically without the addition of any material. The third group was the as-received group. Ten specimens were investigated for each group. <br /> The results for surface hardness using the ANOVA test showed a statistically significant difference between the groups (p-value=0.0097). The nanocarbon coated group was (343 HV), while the mechanically-treated and as-received groups were (328 HV). Also, the yield strength ANOVA test showed a statistically significant difference between the groups (p-value=0.0184). The nanocarbon coated group was (255 MPa), the mechanically-treated (327 MPa), and the as-received (338 MPa). <br /> On the other hand, the results for roughness, friction, corrosion, and modulus of elasticity showed no statistically significant difference between the three groups. The cytotoxicity results for the nanocarbon coated group showed no statistically significant difference when compared to the as-received wires, although it showed variability in the results, this high sample variance and standard deviation relative to the mean, requires further investigation. The mechanically-treated wires showed the highest cytotoxicity. <br /> Clinically, improving the strength and hardness of the NiTi archwires will produce a wire that is more durable and less likely to break, which happens frequently with smaller diameters. If proven to be sufficiently biocompatible, this could be a good improvement on the current available archwires.