Effectiveness of Tubular Coaxial Nickel-titanium and Copper Nickel-titanium Orthodontic Aligning Archwires

At the day of bonding, 0.016-inch archwire will be placed for the TuNT group. Eight weeks later it will be replaced by the 0.018-inch archwire for another eight weeks. While, for the CuNT group, 0.014-inch archwire will be placed at the day of bonding and eight weeks later it will be replaced by the 0.018-inch archwire for another eight weeks. Archwires will be tied to the bracket by elastomeric modules which will be changed every 4 weeks. A good-quality alginate impression for the lower arch should be taken pre-treatment and after 4, 8, 12 and 16 weeks and a stone study model is obtained. Periapical X-ray for the mandibular central incisors will be taken pre-treatment and after 16 weeks. The participants will be provided by a visual analog scale (0-10) to record their pain perception during the first week after each wire placement.