John J Warren1, Maria C P Saraiva2. 1. Professor, University of Iowa College of Dentistry, Department of Preventive & Community Dentistry, The University of Iowa, N-337 Dental Science Building, Iowa City, IA 52242-1010, USA, Tel.: +1 319 335 7205; fax: +1 319 335 7187. Electronic address: john-warren@uiowa.edu. 2. Associate Professor, University of São Paulo School of Dentistry of Ribeirão Preto, Department of Pediatric Dentistry, School of Dentistry, Av do Café s/n, Ribeirão Preto CEP-14040-904, Brazil. Electronic address: mdsaraiv@umich.edu.