This study aimed to evaluate postoperative pain intensity after glide-path preparation with the ProGlider (PG) and WaveOne Gold Glider (WOGG) systems in asymptomatic teeth with necrotic pulp and periapical lesions.Maxillary and mandibular molars with chronic apical periodontitis of 78 patients (age, 18-65 years) were included. The patients were randomly divided into three groups: control (n = 26), PG (n = 26), and WOGG (n = 26). All systems were used according to the manufacturer's instructions, and all root canal treatments were completed by a single operator within two sessions. Postoperative pain was assessed using a numerical rating scale (NRS) at 6, 12, 18, 24, 48, and 72 h. The intake of prescribed analgesics and abscess formation were also recorded.

Pain after root canal treatment is an important complication encountered in endodontic practice, with a reported prevalence of 3%-58%. Severe pain may start even 24 to 48 h after treatment. Postoperative pain has a complex etiology, including treatment factors under the control of the clinician, microbial factors related to the contents of infected root canals, patient demographic factors (patient sex and age, among others), immunological factors, local tissue changes, and psychological factors. Debris extrusion to the periapical tissues during root canal instrumentation can significantly influence the incidence and intensity of postoperative pain. The root canal instrumentation technique may play an important role in the occurrence of postoperative pain as it can induce an acute inflammatory response following periapical extrusion of necrotic tissues, infected debris, and bacteria. Previous clinical trials have evaluated the effect of reciprocation and continuous rotation kinematics on debris extrusion and postoperative pain; however, their results are conflicting.

The glide path is defined as a straight tunnel extending from the canal orifice to the physiological apical foramen. Glide-path preparation may prevent complications of root canal instrumentation; reduce risk of instrument failure, debris extrusion, and postoperative pain; and preserve root canal anatomy, thereby reducing the risk of transportation, perforation, and step and zip formation. Many NiTi glide-path file systems of different sizes and metallurgical properties have been introduced to date. Recently, a new single glide-path file system was introduced with the aim of reducing the number of files used and simplifying glide-path instrumentation.

The effect of glide-path file systems on postoperative pain has been studied previously. However, to the best of investigators' knowledge, there are no data comparing PG and WOGG glide-path files in terms of postoperative pain in asymptomatic teeth with necrotic pulp and periapical lesions. Therefore, the purpose of this in vivo study was to evaluate the incidence and intensity of postoperative pain in asymptomatic maxillary and mandibular molars with necrotic pulp and periapical lesions after glide-path preparation with a stainless-steel K-file and PG and WOGG glide-path file systems. The null hypothesis was that there is no difference in the incidence and intensity of postoperative pain between glide-path preparation techniques.

Inclusion Criteria:

• Asymptomatic maxillary and mandibular first and second molars diagnosed with chronic apical periodontitis in healthy patients
• Patients between 18-65 years old
• Patients who had not taken antidepressants, sedative drugs, analgesics and/or anti-inflammatory drugs
• Patients who could understand the use of numeric rating scale (NRS) for pain.

Exclusion Criteria:

• Patients who were allergic to anesthetics and non-steroidal drugs
• Patients who use immunosuppressants
• Patients who are pregnant or breastfeeding
• Patients with systemic infections.
• Teeth with advanced periodontal disease
• Teeth with acute pain
• Teeth with calcified or resorbed canals
• Teeth with complex root canal anatomy
• Teeth with vital pulp
• Unrestorable teeth
• Presence of cracks and/or fractures
• Teeth associated with acute and chronic apical abscesses

The patient and statistician were blind to the groups but the operator who performed all treatment procedures could not be blinded to the study group owing to the study design.