Effect of low – level laser irradiation on healing process of lower lip hypoesthesia following sagittal split ramus osteotomy

Evaluate the influences of low-level laser therapy on improvement of lower lip neurosensory disturbance following sagittal split ramus osteotomy.

Controlled clinical trial with parallel groups, double blinded, individual simple random sampling

40 patients will require lower jaw orthognathic surgery referring to the maxillofacial surgery ward, Taleghani hospital, Tehran are included in the study.The patients will be selected in an individual simple random sampling. Diode laser irradiation will be performed in intervention group patients following lower jaw sagittal osteotomy surgery. The examiner and the patients are blinded to the groups. After that the sensory signs of the patients will be assessed in 3, 6, and 12 months periods.

Inclusion criteria: Patients who undergo sagittal split osteotomy surgery, Nerve damage is as neuropraxia, No technical error is occurred during surgery, No previous nerve damage is mentioned, No previous facial surgery is mentioned, Patients are not medically compromised, Patients do not consume anticonvulsants and antidepressants drugs. Exclusion criteria: History of neurosensory disturbance in the facial area, Inappropriate surgical technique, Neurotmesis or axonotmesis happening, Uncooperative patients

Intervention group patients will undergone laser therapy by GaAlAs diode laser. Laser irradiation would be performed 6, 24, 48, and 72 hours following surgery and every other day for the next two weeks (10 sessions). Diode laser wavelength is 810 nm, the power density is 8.4 j/cm2, power is 70 mW, and the beam diameter is 8mm. Control group: The probe is moved on the patients' faces whilst the laser unit is off.

Patient's satisfaction, recovery of facial skin sensation

The patients will be divided into the groups in an individual simple random sampling (SRS) manner. In this order random number table will be used. Any of 500 referred patients to the hospital who need orthognathic surgery will have a number. These numbers will be put in the number table without any pattern and totally disorderly. The numbers are found by a second blinded person in order to allocation concealment. At first a point is selected to start. By default, the direction from left to right is set. By moving on the table each number will be recorded which is the person who is included in the study. By default, numbers under 250 are included in the intervention group and numbers over 250 are included in control group. This process will be continued until 40 patients (sample size) are completed.

Every patient is included in control or intervention group randomly and is not informed about that.In control group the probe is used whilst the laser unit is off. In this order the patients will not understand that whether the laser is irradiated or not and are blinded to the survey. The examiner who assesses the outcomes is not aware that each patient is whether in the intervention group or not. Actually the study is designed to be double blinded.