1. Department of Stomatology, The Second Hospital of Tangshan City, Tangshan, Hebei 063000, P.R. China
2. Department of Stomatology, North China University of Science And Technology Affiliated Hospital, Tangshan, Hebei 063000, P.R. China
3. Department of Stomatology, The Third Hospital of Shijiazhuang City, Shijiazhuang, Hebei 050011, P.R. China
4. Department of Stomatology, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei 050011, P.R. China