M. Omidkhoda - School of Dentistry, Mashhad university of Medical sciences
Z. Sahebnasagh - School of Dentistry, Mashhad university of Medical sciences
M. Poosti - Islamic Azad University,Dental Branch, Tehran, Iran
M. Yaghoobi - School of Dentistry, Mashhad university of Medical sciences
A. Izadpanahi - Ferdowsi University, Mashhad ,Iran

Introduction: Since orthodontic therapy may have detrimental effects to the tooth structures or periodontium, practitioners recommend their patients to use different mouth washes. These chemical agents may be potentially damaging to metal components of orthodontic appliances. The aim of the present study was to evaluate the effect of three common mouthwashes on mechanical properties of NiTi orthodontic wires. Materials and Methods: ۲۷ pieces of ۰.۰۱۶inch Niti wires were randomly assigned into ۹ groups including ۳ control and ۶ experimental groups. After the first month of immersion in artificial saliva, the wires in ۳ groups were immersed in Chlorhexidine, Persica and Hydrogene Peroxide for ۳۰min, ۱.۵h and ۱.۵h respectively. The control groups included as received wires, wires immersed only in artificial saliva and Saliva + tooth brush. Mechanical properties of the wires were evaluated by three point deflection test. Two way ANOVA and Tukey tests were used to compare groups. Results: Persica caused significantly lower force in ۲ and ۳ mm deflection during loading compared to Peroxide, chlorhexidine and “as received”. Chlorhexidine also significantly reduced the loading force during ۳mm deflection in comparison to saliva control. In ۲ mm deflection during unloading Persica significantly reduced unloading force in comparison to all groups including: chlorhexidine, peroxide, saliva control and “as received”. It is also seen that chlorhexidine caused lower force compared to saliva control. Then, NiTi wires in ۳ groups underwent ۳۲۰۰ tooth brushing cycles and were compared with each other and with ۲ control groups (saliva + brushing and "as received" ) by Tukey test. The results showed that only in ۳mm loading deflection there was significant difference between Persica and Peroxide, and also between peroxide and as received wires.Conclusion: Persica was the most effective mouthwash on mechanical properties of NITI wires.