1. Division of Oral and Maxillofacial Radiology, Department of Basic Science, Faculty of Dentistry, University of Health Sciences, Vientiane, Laos.
2. Department of Oral and Maxillofacial Radiology and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Korea.
3. Department of Dental Hygiene, Kyungbok University, Pocheon, Korea.
4. Department of Oral and Maxillofacial Radiology, Seoul National University Dental Hospital, Seoul, Korea.