Electromyographic˚˚ Study˚˚ of˚˚ the˚˚ Masseter˚˚ Muscle˚˚ After˚˚ Low-Level˚˚ Laser˚˚ Therapy˚˚ in˚˚ Patients˚˚ Undergoing˚˚ Extraction˚˚ of˚˚ Retained˚˚ Lower˚˚ Third˚˚ Molars˚ Estudio˚˚ Electromiográfico˚˚ del˚˚ Músculo˚˚ Masetero˚˚ tras˚˚ Terapia˚˚ con˚˚ Láser˚˚ de˚˚ BajaIntensi- dad˚˚ en˚˚ Pacientes˚˚ Sometidos˚˚ a˚˚ Extracción˚˚ de˚˚ Tercer˚˚ Molar˚˚ Mandibular˚˚ Retenido

The surgery for extraction of the retained lower third molar is one of the most commonly performed procedures in the field of maxillofacial surgery. During this procedure, the surgical trauma can cause damage to the function of muscles involved in mandibular movements, such as the masseter muscle. In order to accelerate post-surgical recovery, many physiotherapy resources are employed, including laser therapy. The aim was to analyze the electrical activity of the masseter muscle treated with Low-level Laser (LLL) after surgical trauma. Assessments of masseter muscle on a sample of 60 patients were performed by surface electromyography in four instances: immediate preoperative, postoperative at 7, 14 and 21 days. The patients were divided into two groups: 1- untreated group with LLL in the postoperative; 2- group treated with LLL (810 nm; 10 J/cm2 ) in the immediate postoperative and at 3, 6 and 9 days after surgery. On the seventh day after surgery 23.3 % of the patients in the group receiving LLL showed recovery of their muscle activity as they presented in the immediate preoperative, versus only 3.3 % of the untreated group. On the 14 th day, 73.3% of treated patients showed functional rehabilitation, versus 6.7% in the untreated group, and on the 21st, 80% versus 10% in the untreated group. On the 14 th postoperative day the electrical activity of the masseter muscle treated with LLL after surgical trauma was compatible with a condition of complete functional recovery. The findings of this electromyographic study indicated that LLL proved to be an efficient physiotherapeutic method for stimulating the masseter muscle functional recovery after surgery of retained lower third molars.