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

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: Prolonged intraoral exposure of various orthodontic archwires alters surface elements but has minimal impact on cytotoxicity.