1. Department of Oral Radiology, Hospital of Stomatology, Jilin University, Changchun 130021, P. R. China
2. Jilin Provincial Key Laboratory of Tooth Development and Bone Remodeling, School and Hospital of Stomatology, Jilin University, Changchun 130021, P. R. China
3. Department of Oral Radiology, School of Stomatology, China Medical University, Shenyang 110002, P. R. China
4. Department of Orthodontics, School of Stomatology, China Medical University, Shenyang 110002, P. R. China