1. State Key Laboratory of Oral Diseases, West China Hospital of Stomatology; Sichuan University; Chengdu 610041 P. R. China
2. Department of Oral and Maxillofacial Surgery, The Second Xiangya Hospital; Central South University; Changsha 410011 P. R. China
3. Air Force Dujiangyan Aviation Medicine Evaluation and Train Center; No. 18, Juqing Road, Dujiangyan; Chengdu 611830 Sichuan P. R. China
4. Department of Oral & Maxillofacial surgery; The First Affiliated Hospital, College of Medicine, Zhejiang University; Hangzhou 310006 P. R. China