1. Department of General Surgery, The First Affiliated Hospital, Sun Yat-sen University, No. 58 Zhongshan 2nd Road, 510080 Guangzhou, China P.R.
2. Department of Oral and Maxillofacial Surgery, Shanghai Ninth People–s Hospital affiliated to Shanghai Jiao Tong University School of Medicine, 639 Zhizaoju Road, Huangpu, 200011 Shanghai, China P.R.