The present study has the objective of evaluating whether the previous therapy with low intensity laser, through its analgesic effect, can promote a greater comfort specifically for patient with pulpitis in mandibular molars. 75 patients with pain from mandibular molar pulpitis will be selected for this study (randomized and double blind) and divided into 3 groups (n = 25): Group 1 - Pulse Laser (880nm, 30mW, 3,6J / cm², 25Hz) ; Group 2 - Continuous Laser (880nm; 30mW; 3.6J / cm²); Group 3 - Placebo. The efficacy of the laser will be assessed using the VAS scale 10 minutes after the laser application, immediately before the blockade is performed.

Anxiety, pain and discomfort are situations of great stress in the daily routine of clinical practice, and especially in the practice of the dental emergency sector. Several studies have concluded that low-intensity laser therapy has been shown to be effective in pain management. However, the majority report the use of laser in the treatment of chronic pain, few studies show its application in acute pain and only one study evaluated the effect of low laser on acute pain of pulp inflammation, but with other parameters. In addition, because of the inflammatory process and several factors of unknown origin, the anesthetic agent can not always promote complete analgesia, especially when faced with mandibular molars. Therefore, the present study has the objective of evaluating whether the previous therapy with low intensity laser, through its analgesic effect, can promote a greater comfort specifically for this type of patient. 75 patients with pain from mandibular molar pulpitis will be selected for this study (randomized and double blind) and divided into 3 groups (n = 25): Group 1 - Pulse Laser (880nm, 30mW, 3,6J / cm², 25Hz) ; Group 2 - Continuous Laser (880nm; 30mW; 3.6J / cm²); Group 3 - Placebo. The pain will be evaluated by means of an VAS score in 6 different times: initial pain, immediately after and 10 minutes after irradiation with the laser, 10 minutes after inferior alveolar nerve block (IANB), during conventional endodontic treatment, after the end of the procedure. (T0, T1, T1 ', T2, T3 and T4). The efficacy of the laser application will be assessed using the VAS scale 10 minutes after the laser application, immediately before the blockade is performed. The use of the laser will be considered effective if the patient reports a reduction in the VAS scale of 2 points, between the initial moment and 10 minutes after the laser application. Analgesia will be evaluated during the pulpectomy procedure with the use of the verbal analogue scale 0 to 3. Analgesic effect will be considered if the professional can finish the procedure without the patient reporting 2 or 3 on this scale. The data obtained between the different groups and schedules will be compared statistically, and the statistical test chosen will depend on the normality of the data. The data obtained between the different groups and times will be compared statistically, and the statistical test chosen will depend on the normality of the data.

Inclusion Criteria:

• ASA I patients, according to the classification of the American Society of Anesthesiology (ASA)
• 18 and 50 years
• Systolic pressure below 140 mmHg and diastolic below 90 mmHg and heart rate between 70 - / + 20 beats / minute
• Pulpectomy in the first and / or lower second molars, which has at least one adjacent molar tooth and a contralateral canine; or absence of deep cavities, extensive restorations, advanced periodontal disease and no history of trauma or sensitivity.

Exclusion Criteria:

• Patients with a history of sensitivity to local anesthetics and sulfur
• Pregnant or suspected of pregnancy
• Users of medications that may interact with the local anesthetic, such as, anxiolytics, antidepressants, antipsychotics, β-blockers and antihistaminic agents
• Patients with septic process near the injection site
• Patients under orthodontic treatment
• Patients with heart disease, neurological disease, hyperthyroidism and diabetes; drug users.