The Impact of Intraoral Exposure on Elemental Composition and Cytotoxicity of Commonly Used Orthodontic Archwires: A...

To evaluate and compare the surface elemental composition and cytotoxicity of round and rectangular nickel-titanium (NiTi) and stainless steel (SS) archwires before and after 4 and 8 weeks of intraoral exposure.

Four groups of archwires (0.018 NiTi, 0.018 SS, 0.019 × 0.025 NiTi, and 0.019 × 0.025 SS), with five samples in each group, were used as as-received controls from the manufacturer. Each of the eight study groups included five samples, and the wires were retrieved after intraoral exposure of 4 weeks in four groups and 8 weeks in four other groups. The surface elemental composition and cytotoxicity of all samples were assessed using energy-dispersive X-ray analysis and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cytotoxicity test using human gingival fibroblasts. Two-way analysis of variance (ANOVA) was employed to evaluate the effects of wire shape (round vs. rectangular) and time (0, 4, and 8 weeks), as well as their interaction, separately for NiTi and SS wire types. Cell viability was analyzed using two-way ANOVA followed by post hoc tests.

All the rectangular wires showed greater alterations than the round wires. Wires exposed intraorally for 8 weeks exhibited greater changes than those exposed for 4 weeks. NiTi wires showed significant reductions in nickel and titanium, whereas SS wires showed significant reductions in nickel, chromium, and iron, particularly in rectangular wires at 8 weeks. Rectangular NiTi wires exhibited the highest cytotoxicity, followed by round NiTi, rectangular SS, and round SS wires.

Prolonged intraoral exposure of various orthodontic archwires alters surface elements but has minimal impact on cytotoxicity.