“…These include endodontic hand files combined with heat or chemical solvents, engine-driven rotary files, ultrasonic instruments, heat-carrying instruments, paper points with chemicals, and lasers (7,8). Two nickel-titanium (NiTi) systems have recently introduced rotary instruments specifically designed for removing semisolid filling materials: the Mtwo R (retreatment) rotary files (Sweden & Martina, Padova, Italy) and the ProTaper Universal retreatment files (Dentsply-Maillefer, Ballaigues, Switzerland).…”