Autoclave sterilization of uncoated and coated NiTi wires and possible effects on the mechanical properties and surface roughness

Introduction: The frequency of patients’ exposure to infection and cross contaminated dental materials raises concern about sterilization of orthodontic arch wires.
Objective: To explore if autoclave sterilization may modify the mechanical properties and surface roughness of NiTi arch wires or not.
Methods: In the present study a total number of ninety maxillary superelastic NiTi wires with a diameter of 0.016” were used. They were equally divided into three groups. Group 1: uncoated NiTi wires (OrthoOrganizers), group 2: teflon coated NiTi wires (OrthoOrganizers), group 3: aesthetic NiTi wire (Jiscop). The three groups were examined using three point bending tests and profilometry before and after autoclave sterilization at 134°C for 18 minutes.
Results: The three point bending test revealed statistically significant higher loading forces after sterilization at deflections of 1mm and 2 mm in uncoated NiTi wire and at 1mm in aesthetic NiTi wire. Significant lower loading forces were recorded at deflections of 2mm &3mm in Aesthetic wire. On the other hand, statistically significant lower loading forces after sterilization were detected in teflon coated NiTi wire. As regards the unloading forces, they were significantly lower after sterilization when deflected for 0.5mm, 1.5mm and 2.5 mm in Teflon coated Niti wire. A significant decrease in the elastic modulus was detected in all groups after autoclave sterilization and the profilometry revealed a significant decrease in the surface roughness of uncoated Niti group.
Conclusion: Autoclaving causes significant changes in the mechanical properties and surface roughness of NiTi archwires.