Effect of Low-level Laser Prior to the Induction of Fatigue

Effect of Low-level Laser Administered to the Masseter and Anteriortemporal Muscles Prior to the Induction of Fatigue

The objective of this study is to perform an evaluation of the effect of LLLT on the prevention of fatigue in the masseter and anterior temporal muscles in young individuals with and without TMD.

Male and female individuals aged 18 to 23 years will be evaluated. The Research Diagnostic Criteria for Temporomandibular Disorders will be applied for the determination of the presence or absence of temporomandibular disorder. Each group (with and without temporomandibular disorder) will then be randomly allocated into a control group and experimental group submitted to pre-fatigue low-level laser therapy. Before and after the induction of fatigue, all volunteers will be evaluated with regard to the range of mandibular movement, bite force, sensitivity to palpation of the muscles evaluated and muscle fatigue. Low-level laser therapy will be administered to the masseter and anterior temporal muscles prior to the induction of fatigue, which will be induced with the use of chewing gum. The data will be submitted to descriptive statistical analysis. The chi-square test and Fisher's exact test will be used to establish the associations of the categorical variables. Pearson correlation coefficients will be calculated for the analysis of the correlation of the continuous variables.

Patients with diagnosis of temporomandibular disorder and that are not submitted to pre-fatigue low-level laser therapy

Patients with diagnosis of temporomandibular disorder and that are submitted to pre-fatigue low-level laser therapy

Patients without diagnosis of temporomandibular disorder and that are not submitted to pre-fatigue low-level laser therapy

Patients without diagnosis of temporomandibular disorder and that are submitted to pre-fatigue low-level laser therapy

Patients with diagnosis of temporomandibular disorder and that are submitted to placebo low-level laser treatment

Patients without diagnosis of temporomandibular disorder and that are submitted to placebo low-level laser treatment

Three points will be irradiated over the masseter muscle (upper, middle and lower bundles) and one point will be irradiated over the anterior temporal muscle of each side of the face in the groups submitted to pre-fatigue laser. The following parameters will be employed: wavelength: 780 nm; energy density: 25 J/cm2; output power: 50 mW; power density: 1.25 W/cm2; and exposure time: 20 seconds per points, resulting in a total energy of 1 J per point. The laser will be applied punctually with a conventional tip in contact with the skin considering an area of 0.04 cm2.

The same equipment will be used in the placebo group, but with a pen that emits a red guide light and a warning sound, but without the emission of a laser beam.

A digital dynamometer will be used for the determination of bite force. The measurements will be taken in the region of the 1st molars.

The individuals will be instructed to open their mouths as wide as possible and maximum active vertical mandibular movement (distance between maxillary and mandibular central incisors) will be recorded with the aid of digital calipers. The individuals will then be instructed to repeat the motion with pressure applied to the maxillary and mandibular teeth to obtain maximum passive vertical mandibular movement with the aid of the calipers. These measurements will be made before and after LLLT.

The visual analog scale will be used before and after treatment to record pain upon palpation of the masseter and anterior temporal muscles. This is a numerical scale ranging from 0 (absence of pain) to 10 (worst pain imaginable) points.

Muscle fatigue will be measured using the visual analog scale, which is a subjective measure that consists of a 10-centimeter line with 0 (absence of fatigue) printed at one end and 10 (maximum fatigue) printed at the other end.

Inclusion Criteria: Male and female individuals aged 18 to 23 years with a signed statement of informed consent will be included in the study. Exclusion Criteria: Individuals in orthodontic or orthopedic treatment for the jaws, psychological treatment or physical therapy and those who make use of muscle relaxants, anti-inflammatory agents or bite plates will be excluded from the study.