Effect of ultrasonic activation on the reduction of bacteria and endotoxins in root canals: a randomized clinical trial - Nakamura, Vitor Cesar; Pinheiro, E. T.; Prado, L. C.; Silveira, A. C.; Carvalho, A. P. L.; Mayer, Marcia Pinto Alves; Gavini, G. (International Endodontic Journal, 2018)