1. Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Pokfulam, Hong Kong
2. Department of Endodontics and Operative Dentistry, College of Stomatology, Southern Medical University, No. 1838 North Guangzhou Avenue, Guangzhou 510515, China
3. Faculty of Dentistry, The University of Hong Kong, 34 Hospital Road, Sai Ying Pun, Hong Kong