The main purpose of this study was to investigate the mechanical properties of Ni-Ti coated orthodontic archwires after surface modification. Universal test machine was used to measure the tensile strength of four groups of coated Ni-Ti wires and uncoated control group. Immersion test was applied for 21 days to discover whether the coating would peel off under friction and brushing after immersion. Student's t-test was used to explore any difference between three groups of coated wires and uncoated conventional wires in mechanical properties. The results showed no statistical difference exists between coated Ni-Ti wires and conventional uncoated wires regarding to tensile strength. The load-displacement curve of both wires looked similar. The coating has no effect on the mechanical strength of the base wire. However, after the 21-day immersion test, the epoxy resin coatings were more likely to peel off than Teflon coatings under friction and brushing (P＜0.05). There was no statistical difference between coated wires and conventional uncoated wires with regard to mechanical tensile strength. While orthodontists can achieve the same expected treatment result with esthetic wires, the issue of preventing coatings from peeling off needs further studies.
