1. Department of Prosthodontics, School and Hospital of Stomatology, China Medical University, Liaoning Provincial Key Laboratory of Oral Diseases, Shenyang 110002, China
2. Department of Pediatric Dentistry, Dalian Stomatological Hospital, Dalian, China
3. Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China