Introduction: The extraction of impacted mandibular third molars is one of the most frequent and delicate surgery that the dentist is faced in clinical practice. Minimize post-operative, not interfering with the quality of life of patients is the major objective of the surgeon. Thus ultrasonic surgery comes up as an alternative to osteotomy with conventional rotary instruments. Objectives: Evaluate the applicability of ultrasonic surgery by doing an analysis of the available evidence in the literature, using a methodology consistent with a systematic review. Compare with a randomized controlled clinical trial signals and post-operative symptoms (pain, swelling, trismus, paresthesia, bleeding, influence of surgical difficulty and duration of surgery) at the extraction of impacted mandibular third molars using two surgical techniques: ultrasonic surgery and conventional rotary osteotomy. Materials and Methods: As part of the systematic review, after eligibility criteria defined the PICOT question determined, a search was made in primary and mixed databases: MEDLINE, PubMed, Cochrane Library, EBSCO, B-On with different combinations of MesH terms with the boolean connector AND. Two independent observers performed the data collection and analysis, and all studies included in the systematic review were subjected to evaluation of their methodological quality. Under the randomized controlled trial, the sample comprised 30 patients divided equally and randomly into two groups: the test group - ultrasonic technique; and control group - conventional rotatory technique. All surgeries were timed. Swelling parameters, trismus and paresthesia were evaluated on the day of surgery and at 3rd, 5th and 7th post-operative day. Intraoperative bleeding was evaluated during surgery. Postoperative pain was evaluated daily by the patient through a VAS and the number of ingested analgesics. Results: Systematic Review included 9 clinical trials, 1 systematic review and 2 meta-analyzes. Comparing the signs and symptoms between two surgical techniques, there was lower levels of pain, edema, trismus and intraoperative bleeding in piezo surgery. On the other way, surgical time was longer in this technique. This clinical trial revealed similar results to those described in the literature. Pain, swelling and trismus presents better results with ultrasonic technique, but without statistical significance. Intra-operative bleeding was significantly lower with ultrasonic surgery (t (28) = 3.258; p = 0.003). Operative time was significantly higher in extractions involving osteotomy and cutting crown and roots either with conventional technique (p = 0.020) and ultrasonic technique (p= 0.039). Ultrasonic technique regardless of surgical difficulty, was more time-consuming compared to conventional technique, without statistical significance (t (28) = - 1.12, p = 0.271). Conclusions: Despite the high cost of the equipment and longer surgical time, lower intensity of post-operative signs and symptoms associated with the inherent technical advantages, makes ultrasonic surgery a favorable therapeutic option, especially in cases where the maintenance of noble anatomical structures is the most important risk factor. Keywords: ultrasonic surgery, impacted mandibular third molars 1, post-operative symptoms