Study aim: Comparison of the effect of Carvacrol gel, and Chlorhexidine in reducing postoperative pain, and dry socket after surgical removal of impacted mandibular third molars Design: Randomized non-blinded clinical trial with 4 parallel group design of 80 patients. Patients will be assigned to the study groups using simple randomization method. Settings and conduct: This clinical trial will be performed on 80 patients referred to the Oral and Maxillofacial Surgery Department of Tabriz Dental School who are candidates for mandibular third molar surgery. After obtaining the inclusion criteria and obtaining informed and written consent, using simple randomization method, patients will be assigned to the study groups: Group 1: which is the control group Group 2: Wash only before the surgery with chlorhexidine mouthwash Group 3: For this group, after surgery carvacrol gel is placed on the wound site (inside the tooth socket) Group 4: The group receiving carvacrol-free gel (To remove the base effect) Participants/Inclusion and exclusion criteria: Inclusion criteria: All adult patients (over 18 years old) without any systemic disease Absent history of dry socket Having one or two impacted wisdom teeth (surgery on one side only) The presence of adjacent second molars No antibiotics and anti-inflammatory intake at least 7 days before surgery) Exclusion criteria: Hypersensitivity to local anesthetics History of smoking Intervention groups: Group I: which is the control group, Group II: Rinse once with chlorhexidine mouthwash pre-operatively, Group III: in which 0.5 % w/w Carvacrol-based gel is placed in the socket after surgical extraction of third molar, Group IV: vehicle gel treated group Main outcome variables: severity of pain; Occurrence or non-occurrence of dry socket; the number of pain relief tablets taken