1. Department of Orthodontics; The Affiliated Qingdao Municipal Hospital, Qingdao University; Qingdao Shandong Province 266011 People's Republic of China
2. Department of Orthodontics; Jinan Stomatological Hospital; Jinan Shandong Province 250001 People's Republic of China
3. Department of Orthodontics; Weihai Stomatological Hospital; Weihai Shandong Province 264200 People's Republic of China