Influence of preflaring on the accuracy of length determination with four electronic apex locators - Camargo, Éricson Janolio de; Zapata, Ronald Ordinola; Medeiros, Paulo Leal; Bramante, Clóvis Monteiro; Bernardineli, Norberti; Garcia, Roberto Brandão; Moraes, Ivaldo Gomes de; Duarte, Marco Antônio Húngaro (Journal of Endodontics, 2009)