Comparison of three retreatment techniques with ultrasonic activation in flattened canals using micro-computed tomography and scanning electron microscopy - Bernardes, R. A.; Duarte, Marco Antonio Hungaro; Vivan, Rodrigo Ricci; Alcalde, Murilo Priori; Vasconcelos, B. C.; Bramante, Clovis Monteiro (International Endodontic Journal, 2016)