Orthodontic treatment time in 2- and 4-premolar-extraction protocols - Janson, Guilherme dos Reis Pereira; Maria, Fábio Rogério Torres; Barros, Sérgio Estelita Cavalcante; Freitas, Marcos Roberto de; Henriques, José Fernando Castanha (American Journal of Orthodontics and Dentofacial Orthopedics, 2006)