The process of non-surgical retreatment includes removing the previous root canal filling materials, disinfecting and sealing the root canal system to prevent re-infection. Gutta-percha is the most common root canal filling material used with various types of sealers. To remove gutta-percha, solvent has been suggested because of its ability to dissolve gutta-percha. The new formula, under the brand name, GuttaClear, has been investigated for its comparable dissolving ability and lower cytotoxicity when compared with others that are currently used. However, no information is currently available of GuttaClear solvent concerning postoperative pain. Therefore, the present study will evaluate postoperative pain after non-surgical retreatment cases using GuttaClear as a solvent compared with no solvent used. Sixty participants are chosen and distributed into 2 groups, randomly. After the procedures, participants will receive the questionnaires about postoperative pain and the amount of medication intake. Both will be recorded at six time periods: (1) immediately after procedure; (2) 6 hours after procedure; (3) 12 hours after procedure; (4) 24 hours after procedure; (5) 48 hours after procedure and (6) 72 hours after procedure.

Inclusion Criteria:

• not be contra-indicated with medication used in this study (ibuprofen)
• have a previously treated endodontic single-root tooth with the need of retreatment
• all those teeth must be restorable
• old root canal filling materials must be located at 1 to 3 mm from the radiographic apex in the periapical radiograph

Exclusion Criteria:

• open apex, root resorption or root perforation
• participants presenting pre-operative pain and/or swelling at the appointment visit
• taking analgesics or antibiotics less than one week before appointment visit
• experiencing problems in completing the pain questionnaires
• tooth which does not contain gutta-percha
• cannot be patent through the apex at the appointment visit