Alcota-Rojas, M.; Compán-Catenacci, G.; Salinas-Castro, J. C.; Palma-Eyzaguirre, A. M. Comparative in Vitro Study of Root Canal Transportation, Using Three Nickel-Titanium Rotary Systems: Hero Shaper, Protaper Universal. Rev Fac Odontol Univ Antioq 2011, 23, 9-21.