Endodontic treatment will be performed in teeth with necrotic pulp and periapical periodontitis. Local anaesthesia will be provided (2% Novocaine with 1:80,000 epinephrine), isolation with rubber dam and standard access cavity preparation will be done.Using 2.5 % sodium hypochlorite, canal negotiation will be done. Coronal flaring with # 2 and #3 Gates-Glidden drills will be done. The canals will be obturated with gutta-percha and epoxy resin sealer. The treatments will be carried out in single-visit. In this group, intervention will be carried out by the Reciproc motor (VDW, Germany) and Reciproc Blue single-file system (VDW, Germany). The intervention is root canal treatment with the Reciproc Blue single-file system.

In this group, OneShape rotational single-file system (Micro Mega, France) will be used as single-file system according to the manufacturer's instruction.

As a control group, Protaper (Dentsply, Mailleffer, Switzerland) will be used according to the manufacturer's instruction.

The device is moving in CW and CCW direction with different angles. It is a single-file endodontic file. The intervention is Reciproc Blue reciprocating single-file system.

A VAS scale will be used for the postoperative pain level. The patients will noted their postoperative pain level according to the VAS scale during the follow-up period.

The patients will record the consumption of the analgesic during the 7 days of follow-up.