1. Department of Stomatology, Affiliated Hospital of Hebei University, Baoding, Hebei 071000, P.R. China
2. Department of Stomatology, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei 050017, P.R. China
3. Department of Stomatology, People's Hospital of Shijiazhuang, Shijiazhuang, Hebei 050000, P.R. China
4. Department of Cardiology, Zhangjiakou First Hospital, Zhangjiakou, Hebei 075000, P.R. China