The purpose of this prospective, randomized, double-blind study was to compare the prospective pain in asymptomatic mandibular molar teeth with necrotic pulp and periapical lesion using three different instrumentation files: Hand, Protaper Universal, and Wave-One files.

ProTaper Universal system is one of the conventional multi-file rotary systems that prepared root canals with six files: three shaping files and three finishing files. A unique design element is varying tapers along the instruments' long axes. The three shaping files have tapers that increase coronally, and the reverse pattern is seen in the five finishing files. Wave-One is reciprocation-based systems that instrumented root canals with only single file. Some studies demonstrated that it has outperformed conventional continuous rotary nickel-titanium (NiTi) preparation in some aspects. The reciprocating motion of Wave-One relieves the stress on the file by special counterclockwise (cutting action) and clockwise (release of the instrument) movements and, therefore, extends the durability of a NiTi instrument and increases its fatigue resistance in comparison with continuous rotation motion.

Inclusion Criteria:

• Healthy patient

Exclusion Criteria:

• Allergy to anesthetics, pregnancy, breastfeeding, vital teeth, unrestorable teeth, and teeth associated with pain or swelling