1. Department of Oral Maxillofacial Surgery, Stomatology Hospital of Xi'an Jiaotong University College of Medicine, Xi'an, Shaanxi, P. R. China
2. Key Laboratory of Environment and Genes Related to Diseases, College of Medicine, Xi'an Jiaotong University, Xi'an, Shaanxi, P. R. China
3. Department of General Surgery, the Second Affiliated Hospital, School of Medicine, Xi'an Jiaotong University, Xi'an, Shaanxi, P. R. China