Endodontic Treatment of Maxillary Premolar with Three Root Canals Using Optical Microscope and NiTi Rotatory Files System - João Bosco Formiga Relvas; Fredsom Marcio Acris de Carvalho; André Augusto Franco Marques; Emílio Carlos Sponchiado; Lucas da Fonseca Roberti Garcia (Case Reports in Dentistry)