1. Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Pl. Ann Arbor Michigan 48108
2. Department of Pediatric Dentistry School and Hospital of Stomatology Peking University 22 South Avenue Zhongguancun, Haidian District Beijing 100081 China
3. Facility for Electron Microscopy Research Department of Anatomy and Cell Biology and Faculty of Dentistry McGill University 3640 University Street Montreal Quebec Canada H3A 2B2