The removal of third molars should be considered to avoid problems such as cysts and other complications. Surgical intervention with the manipulation of oral tissues has the undesirable postoperative effects of pain, trismus (limited mouth opening) and edema. Photobiomodulation has also proved effective regarding reductions in pain, edema and trismus. The aim of the present study was to evaluate the effectiveness of photobiomodulation for the conditioning of tissues involved in the surgical removal of impacted mandibular third molars in terms of reducing or eliminating postoperative pain, trismus and edema.

The investigator will select 62 patients from Nove de Julho Clinics, minimal 18 years old, with impacted third molar teeth. The volunteers will be randomly allocated to two groups using a block randomization process: photobiomodulation group (PG) and sham group (SG). The same surgeon and assistant performed all operations. The surgeon, assistant and patients will be all blinded to the LED treatment protocol. The participants in the active photobiomodulation group will be irradiated with infrared LED at a wavelength of 850 nm 08J 80 seconds perpendicular to the surface of the skin in gentle stationary contact at three extraoral points. For the participants in the sham group, a device with a similar appearance will be used that did not emit radiation. Treatment will be administered one hour prior to the surgical procedure as well as 48 hours and seven days (removal of sutures) after the first irradiation. The visual analog scale will be used for the measurement of pain intensity, facial measurements evaluated edema. Mouth opening range will be measured with sterilized manual calipers between the incisal edge of the maxillary and mandibular central incisors. The distribution of the data (normal or non-normal) will be determined using the Shapiro-Wilks test. Data with normal distribution will be analyzed using two-way repeated-measures analysis of variance (ANOVA), the t-test for two groups with independent measures and the paired t-test for two groups with dependent measures. Data with non-normal distribution will be analyzed using the Wilcoxon test for paired data and the Mann-Whitney test for independent data. Categorical data will be analyzed using Fisher's exact test for independent data and McNemar's test for paired data. The significance level will be set at α = 0.05.

Inclusion Criteria:

• male and female adults (18 years of age or older)
• no tumors in the oral region,
• not having undergone psychiatric treatment in the previous year,
• good general health,
• satisfactory oral hygiene,
• impacted mandibular third molar
• signed statement of informed consent.

Exclusion Criteria:

• habitual use of analgesic or anti-inflammatory medication for other comorbidities,
• undergoing neurological/psychiatric treatment,
• teeth with lesions to be treated in the same hemi-arch as the tooth to be removed,
• systemic disease,
• current smoking habit,
• pericoronitis in the previous 30 days,
• pregnant or nursing women,
• poor oral hygiene,
• photosensitivity disorder,
• tumor in the oral region,
• heart disease,
• diabetes,
• blood dyscrasia,
• chemical dependency,
• allergy to medications used in the study,
• ankylosis of the temporomandibular joint
• intraoperative complications with surgery time exceeding 90 minutes.

An external investigator was assigned to perform randomization. Containing the type of treatment to be used inside, unidentified envelopes were drawn among the participants, resulting in two groups.