In this study, an orthodontic arch wire of Ni-Ti alloy made by Germany in four different mouthwashes contain fluoride was investigated in mechanical behavior. This research focused on the mechanical behavior changes in different mouthwashes. The Mouthwashes were chosen from most popular one in Iran including Oral-B, Gum, and Behsa Mouthwash. The wires after 3 month in touch with mouthwashes were studied and the result was presented. The result show that the lowest power to reshape the wire, is for the wire in Crest case (3). The maximum power assigns to wire in Behsa case (1). Also, the shortest treatment period is for wire in Behsa mouthwash case (1) with 0.087 Nm strain energy and the maximum duration of therapy is related to case (3) Crest mouthwash with 0.039 Nm. Moreover, the wires in Oral-b (0.095 Nm) has the lowest and Gum mouthwash (0.140 Nm) has the highest energy intake. The energy absorbed by the wires in Behsa and Crest is in the middle. Finally, it is proposed that patient could used all mouthwash but based on their condition, one product will be useful.