1. Oral Sciences, Faculty of Dentistry, National University of Singapore, Singapore 119083
2. Discipline of Oral and Maxillofacial Surgery, Faculty of Dentistry, National University of Singapore, Singapore 119083
3. Department of Conservative Dentistry, School of Dentistry, Chonbuk National University, Jeonju 54596, Republic of Korea
4. Department of Cariology, Restorative Sciences and Endodontics, School of Dentistry, University of Michigan, Ann Arbor, MI 48109, USA