In dentistry, one of the most common surgical procedures is the removal of included third molars. This surgery generates great morbidity to patients for causing pain, edema and trismus due to surgical trauma. The use of photobiomodulation (PBM) (low-power laser or light emitting diode - LED) in the postoperative of these procedures has shown excellent results in the control of postoperative sequelae. The objective of the present study is to evaluate the effectiveness of PBM with LED in the control of pain, facial edema, trismus and quality of life resulting from the extraction of retained lower third molars. A randomized, double-blind, placebo-controlled clinical trial involving 34 adult patients, who search the Discipline of Buccomaxillofacial Surgery and Traumatology (CTBMF) II of FO-UFRGS for the removal of included lower third molars will be conducted. Before and after the surgeries, the facial and mouth opening measurements of all patients will be done. Immediately after the surgeries, the patients will be randomized by means of envelopes in two groups. In the LED group the patients will receive daily LED applications (intra oral with 660nm and extra oral with 850nm) from the immediate postoperative to 7 days after the surgical procedure. In the control group the patients will be treated in the same way as in the LED group, however, the person in charge of the application will simulate intraoral and extraoral irradiation with the LED kept off. Pain (EVA and NRS-101), postoperative edema, trismus, temperature, dysphagia and hematomas, as well as the impact of the surgical procedure on patients' quality of life will be evaluated after 1, 2, 5 and 7 days. For the analysis of the oral health impact profile (OHIP-14 Questionnaire) and anxiety analysis (Beck anxiety inventory -BAI) the questionnaires will be applied preoperatively and 7 days after treatment. Initial descriptive analyzes will be performed considering all variables measured in the study, both quantitative (mean and standard deviation) and qualitative (frequencies and percentages). Later, the appropriate statistical tests will be applied for each specific analysis. In all tests, the significance level of 5% probability or the corresponding p-value will be adopted. All analyzes will be performed using the statistical software SAS for Windows, version 9.1.3.

Inclusion Criteria:

• Patients who need surgical removal of retained lower third molars;
• Patients who agree to participate in the study after reading and signing the Term of Consent for Participation in Clinical Research.
• Patients with indication for extraction of lower third molars (recurrent infections, bad position, orthodontic indication) or written professional indication (ASA I - negative medical history), systolic blood pressure less than 140mmHg, and diastolic blood pressure lower than 90mmHg and heart rate values of 70 ± 20 beats / minute and have the upper and lower central incisor teeth.

Exclusion Criteria:

• Patients who have systemic diseases, chronic pain or neurological and psychiatric disorders;
• Claim to be smokers;
• Are using anti-inflammatories, analgesics or bisphosphonates in the last 15 days;
• Present active pericoronaritis;
• Are pregnant;
• are breastfeeding;
• Severe temporomandibular disorders
• Have photo sensitivity history
• Are allergic to any drug used in the research (paracetamol, chlorhexidine 2%)
• Patients presenting radiolucent images associated with the teeth to be extracted
• Patients who present any type of complication during surgery (hemorrhage, operative difficulty, time greater than 90 minutes of surgery), as these cases are not in the standard expected for third molar surgeries. In this case the central action analgesic will be prescribed. These data will not be part of the statistical analysis but will be described and discussed as well as possible adverse effects.

After the suture is completed, the researcher responsible for applying the LED will remove and open the envelope containing the information from the experimental group in which the patient will be inserted and proceed to the experiment. A single examiner will run the daily application of the LED and will not perform any type of evaluation. Surgical procedures will be performed by the same surgeon. The preoperative and postoperative evaluations (1, 2, 5 and 7 days postoperatively) will be done by an examiner who will not be aware of the group in which each patient is allocated. Patients will not be aware of whether or not they received LED irradiation, because the person in charge of the LED application will position the plate in place for intra and extraoral irradiation in all patients and only trigger the light when and where predicted in the specific experimental group. The characteristic sound of the device will be triggered by recording in the sham group.