Effect of ultrasonic activation on the reduction of bacteria and endotoxins in root canals: a randomized clinical trial - Nakamura, V. C; Pinheiro, Ericka Tavares; Prado, Lais Cunha; Silveira, A C; Carvalho, A. P. L; Mayer, Marcia Pinto Alves; Gavini, Giulio (International Endodontic Journal, 2017)