2 Department of Orthodontics and Pediatric Dentistry, School of Dentistry, and Cell and Developmental Biology, School of Medicine, Center for Human Growth and Development, University of Michigan, and Private practice, Ann Arbor, Mich.
3 Department of Experimental and Clinical Medicine, Section of Dentistry (Orthodontics), University of Florence, Florence, Italy, and Department of Orthodontics and Pediatric Dentistry, School of Dentistry, University of Michigan, Ann Arbor, Mich. Electronic address: lorenzo.franchi@unifi.it.