1. Shandong Provincial Key Laboratory of Oral Tissue Regeneration, School of Stomatology, Shandong University, Jinan, Shandong Province, China.
2. Department of Prosthodontics, School of Stomatology, Shandong University, Jinan, Shandong Province, China.
3. Department of Pediatric Dentistry, School of Stomatology, Shandong University, Jinan, Shandong Province, China.
4. Department of Orthodontics, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA, USA.