Study design and participants

This randomized, crossover, double-blind clinical trial was carried out in the oral and maxillofacial department of a clinical university hospital. The sample comprised patients who needed bimaxillary orthognathic surgery including a bilateral sagittal split and Le Fort I osteotomy to correct their dentofacial deformity. All patients underwent preoperative orthodontic treatment to correct tooth position. All patients were operated on by the same surgeon. The inclusion criteria were the following: no facial trauma or inferior alveolar nerve (IAN) injury; no neurosensory disturbance before treatment; third molars removed at least 6 months before the orthognathic surgery; bilateral sagittal split osteotomy on both sides of the jaw taking roughly the same time, with minimal IAN manipulation; and no genioplasty. Exclusion criteria were neurovascular bundle rupture; poor BSSO split; postoperative infection; and missing laser application.

The study was approved by the university research ethics board and has been registered in the clinical trials database ( http://clinicaltrials.gov , protocol No. NCT01530100 ). All subjects signed an informed consent form prior to undergoing treatment and fulfilled the criteria set out without any exclusion.

Surgical procedure

A standard bilateral sagittal split osteotomy and Le Fort I osteotomy were performed. Pre-, intra-, and postoperative medications were standardized and dosed according to the patient’s weight in order to keep the drugs in the same proportion. All patients received antimicrobial prophylaxis (cefazolin preoperatively), steroids (hydrocortisone intraoperatively and dexamethasone postoperatively until the third day after surgery), and analgesics (tramadol intraoperatively and every 8 h during the first 24 h after admission, and ketorolac until 48 h after the operation).

Laser protocol

A gallium–aluminium–arsenide diode low-level laser device (Thera Lase, DMC Brazil; continuous wave, spot size 0.4 mm) was used. The surface exposed to laser therapy was cleaned and air-dried before application. The applications were performed by a single trained professional who did not take part in the surgical procedure.

One side of the face, the ‘irradiated side’, was chosen randomly by draw to receive laser therapy intraorally and extraorally. The laser was applied to four points over the incision line, 1 cm apart, in the immediate postoperative period and at 24, 48, and 72 h after the surgery (wave length ( λ ) = 660 nm (red), energy density (ED) = 5 J/cm ² , time ( t ) = 10 s/point, laser power ( P ) = 20 mW, energy ( E ) = 1.2 J/point). The laser was applied to eight points in the mandibular ramus and body in the immediate postoperative period and at 24, 48, and 72 h after the surgery ( λ = 789 nm (infrared), DE = 30 J/cm ² , t = 20 s/point, P = 60 mW, E = 1.2 J/point). The same exposure was used on two points each of the pre-auricular, jugular-digastric, and submandibular lymph nodes ( Fig. 1 ). The total energy used was 21.6 J per session.

Laser application scheme for the first four postoperative days. (a) Intraoral exposure over the incision line. (b) Extraoral exposure to the mandibular ramus and body, and the pre-auricular, jugular-digastric, and submandibular lymph nodes.

After the fourth day, 10 intraoral applications were performed at 48-h intervals on three points 1 cm apart on the path of the inferior alveolar nerve on the mandibular ridge and three points on the lower labial mucosa. Extraoral applications were performed on two points on the lower lip and nine points 1 cm apart in the chin region ( λ = 780 nm (infrared), DE = 70 J/cm ² , P = 70 mW, t = 40 s/point, E = 2.8 J/point) ( Fig. 2 ). The total energy used was 50.4 J per session.

Laser application scheme after the fourth postoperative day. (a) Three points to the lower labial mucosa. (b) Three points to the path of the inferior alveolar nerve on the mandibular ridge. (c) Two points to the lower lip and nine points to the chin region.

The laser unit was positioned on the same points on the other side of the face, the ‘non-irradiated side’, but was not activated. During all applications patients were blinded with the use of black glasses and listened to music via headphones so that they did not know which side of the face had been irradiated.

Assessment

A single trained individual, blinded to the side of laser application, assessed postoperative swelling and pain.

Swelling size was calculated using the modified formula of Carrillo et al., measuring the distance between the tip of the chin and the lower lobe of the ear immediately postoperatively and then at 72 h, 1 week, 15 days, and 30 days postoperatively. At each time-assessment after the surgery, the mandibular length was subtracted from the baseline length, and the result was divided by the baseline length and multiplied by 100. The baseline length used was the distance measured 2 months postoperatively.

A visual analogue scale (VAS) was used to measure pain intensity in the postoperative period: immediately after the operation and at 24 h, 72 h, and 1 week after the operation. Patients were asked about the degree of pain in each period, with 0 defined as the absence of pain and 10 as the maximum tolerable level of pain.

At each session, patients were observed regarding any possible side effects from LLLT, such as burns or erythema.

Statistical analysis

Data were entered into a Microsoft Excel spreadsheet by one person who was masked to the procedure, and data were imported into IBM SPSS Statistics Version 19 (IBM Corp., Armonk, NY, USA). The Wilcoxon signed-rank test was used to analyze the associations between the variables, comparing the laser-irradiated and non-irradiated groups. The Mann–Whitney test was used to compare the different patients with regard to the influence of the surgical procedure on swelling and pain. Values of P < 0.05 were considered statistically significant.