Objective To investigate mechanic properties of fiber-reinforced composite（FRC） and its influence on maintaining periodontal health. Methods Sixty patients completing orthodontic treatment were randomized into two groups with FRC and multistrand stainless steel wire（MSSW） being applied as fixed lingual retainer. Bleeding index （BI） and pocket depth（PD） were recorded right after, 6 months and 12 months after bonding the retainer. Flexural modulus and maximum shear bond strength were tested for FRC and MSSW. Results Statistical significance was found at the increase of BI from right after bonding, 6 months after to 12 months after for both groups（P0.05）. There were no difference between the two groups at each time point regarding BI and PD（P >0.05）. The flexural modulus and maximum shear bond strength of FRC were both below to that of MSSW under the same test situation（P
