1. Department of Operative Dentistry and Endodontics, Guanghua School of Stomatology, Institute of Stomatological Research, Sun Yat-sen University, Guangzhou, China;
2. Department of Conservative Dentistry, School of Dentistry, Kyungpook National University, Daegu, Korea;
3. Department of Conservative Dentistry, School of Dentistry, KyungHee University, Seoul, Korea;
4. Paediatric Dentistry and Orthodontics, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, China;
5. Department of Oral Biology, School of Dentistry, Medical College of Georgia, Augusta, GA, USA; and