Effect of soft drinks on the physical and chemical features of nickel-titanium-based orthodontic wires

Objective. The purpose of this study was to evaluate the effect of three popular soft drinks on the Young's modulus, hardness, surface topography and chemical composition of widely used nickel-titanium-based orthodontic wires. Materials and methods. Thirty-two specimens (20 mm in length) were cut from the straight portion of pre-formed 0.019 0.025 inch Nitinol Heat-Activated archwires and randomly divided into four groups of eight specimens each: Group A1 (Coca Cola regular); Group A2 (Santal orange juice); Group A3 (Gatorade); Group B (distilled, deionized water; dH2O). Each specimen was immersed in 10 ml of one of the soft drinks or dH2O, control, for 60 min, at 37C. At the end of the soaking time,the Young's modulus and hardness were determined using a nanoindenter. Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM-EDS) was used to characterize the effects on the topography and chemical composition of the wires. Results. No statistically significant differences were found between the groups either in the Young's modulus or in hardness after the selected soaking protocol. Besides some surface colour changes, the topography and the chemical composition of the wires were not affected by the immersion in any of the chosen soft drinks. Conclusions. These in-vitro results suggest that the consumption of soft drinks cannot be acknowledged as one possible reason for the degradation of the physical and chemical properties of heat activated nickel titanium orthodontic wires in patients undergoing fixed orthodontic treatment.