1. Université de Montréal 1 , departement d'anthorpologie, unité d'anthropologie physique. C.P. 6128, succursale Centre-Ville, Montreal ( Quebec ), H3C3J7Canada
2. Institute of Dentistry 2 Department of Pedodontics and Orthodontics, , P.O. Box 41, FIN-00014 , Finland
3. University of Helsinki 2 Department of Pedodontics and Orthodontics, , P.O. Box 41, FIN-00014 , Finland
4. National Public Health Institute 3 , Mannerheimintie 166, 00300Helsinki, Finland
5. Université de Montréal 4 , departement de stomatologie. C.P. 6128, succursale Centre-Ville, Montreal ( Québec ), H3C317Canada