Study Design |
Randomized clinical study |
Cross-sectional study |
Not informed |
Double blind study |
Cross-sectional study |
Sample size |
44 |
26 |
40 |
23 |
86 |
Groups evalu-ated |
Patients with and without TMD. |
Adult women aged from 22 to 82 years. |
Women with and without my-ogenic TMD, aged from 18 to 40 years. |
Women with and without myo-genic TMD, aged from 33 to 49 years. |
Patients with and without TMD, of both genders, aged from 18 to 60 years. |
Symptomatic conditions |
Arthralgia, myofascial pain, limited mouth opening, joint sounds, and jaw locking. |
Myofascial trigger points, for lo-cal pain and referred pain. |
Myofascial pain, limited mouth opening, disc displacement with and without reduction, and arthralgia. |
Myofascial pain. |
Myofascial pain, limited mouth opening, disc dis-placement with and without reduction, and arthralgia. |
Regions/muscles/ orofacial points evalu-ated |
TMDs on both sides |
Masseter and temporal mus-cles, on both sides. |
Masseter and anterior tempo-ral muscles, on both sides. |
Masseter and anterior temporal muscles. |
Masseter and anterior tem-poral muscles, and TMJ, on both sides. |
Thermographic Protocols |
Environmental specifications: Protocol recommended by the Aca-demy of Neuro-Muscular Thermo-graphy. Patient specifications: Clean and dry face; tied hair; 15 mi-nutes of rest to balance facial tem-perature. Equipment and Technical Parame-ters Agema 870 infrared thermography unit. Projections acquired at two sensiti-vities (0.5° and 1.0°C) with an accu-racy of 0.1 °C. |
Environmental specifications: Protocol recommended by the Academy of Neuro-Muscular Thermography. Patient specifications: Do not use cream or makeup; do not use a hair dryer or straightener; do not smoke before the exam; avoid manipulations in the face; do not drink coffee or alcoholic beverages; do not use drugs or substances that alter sympathetic function; keep the hair tied up and covered with a disposable cap. During the examination, the pa-tient remained seated, with the head positioned on a cephalostat, with the muscles relaxed and the teeth spaced apart. Equipment and Technical Pa-rameters ThermaCAM T400 infrared ther-mography unit (FLIR Systems, Wilsonville, USA). Thermal sensitivity of 0.05°C to 30°C; spectral range 7.5 μm-13 μm; special resolution of 320 χ 240 pixels; camera-patient dis-tance of 0.75 m, at an angle of 90°, with the camera lens paral-lel to the region to be evaluated. Skin emissivity value of 0.987. |
Environmental specifications: The patients were acclimatized in a room at 21 °C, for 20 minu-tes. The room was lit by fluo-rescent lamps. Patient specifications: Avoid hot baths; creams and makeup; nasal decongestants; practice vigorous exercise and take stimulant substances be-fore the exam. During the examination, pa-tients remained seated with their torso upright, feet flat on the floor and hands resting on their thighs, keeping the Frank-furt plane parallel to the floor. Objects were removed from the area examined and hair was kept tied up. Markers were used to standar-dize anatomical points in the evaluated muscles. Equipment and Technical Pa-rameters T360 infrared thermography unit (FLIR Systems, Danderyd, Sweden). Emissivity value of 0.98; came-ra-patient distance of 100 cm. |
Environmental specifications: Protocol recommended by the Academy of Neuro-Muscular Thermography. Patient specifications: Do not use cream or ma-keup; do not use a hair dryer or straightener; do not rub or press the skin; keep the hair tied up and covered with a dis-posable cap. During the examination, the pa-tient remained seated, with the head positioned on a cephalostat, with the facial muscles re-laxed and the teeth apart. The Frankfurt plane was kept paral-lel to the horizontal plane. Equipment and Technical Para-meters ThermaCAM T400 infrared ther-mography unit (FLIR Systems, Wilsonville, USA). Thermal sensitivity of 0.05°C at 30°C; spectral range of 7.5-12 μm; spatial resolution of 320 χ 240 pixels; emissivity value of 0.98; camera-patient distance of 0.80 m, at an angle of 90°, with the camera lens parallel to the region to be evaluated. |
Environmental specifica-tions: Protocol recommended by the American Academy of Thermology. Patient specifications: Do not use cream or ma-keup; do not use a hair dryer or straightener; avoid anal-gesics, corticosteroids, and anti-inflammatory agents; do not exercise and do not touch or rub the skin. The patient remained sea-ted for 15 minutes before capturing the images, main-taining an upright posture, with the Camper plane pa-rallel to the horizontal plane. Facial masks were made and used as guides for ana-tomical demarcation of the evaluated regions. Equipment and Technical Parameters T650sc infrared thermog-raphy unit (FLIR Systems, Danderyd, Sweden). Spatial resolution of 640 χ 480 pixels; emissivity value of 0.98; camera-patient distance of 0.80 m. |
Other exams |
Measurement of mouth opening (in |
RDC/TMD. |
RDC/TMD. |
RDC/TMD. |
RDC/TMD. |
performed |
mm). Examination of jaw locking, using the following classification scale: 0 = without locking 1 = mild locking 2 = moderate locking Examination of joint sounds, using the following classification scale: 0 = absence of noise 1 = click, one side only 2 = click, on both sides 3 = click and snap Examination of pain and discomfort in joints and muscles, using a pres-sure algometer. |
Side view photographs of the face. Examination to measure pain in trigger points using algometry. Each patient was instructed to report when they felt initial pain or discomfort, and if the pain was local or if it extended to an-other region. |
Pain evaluation by VAS. |
Digital photographs of the face. Palpation. Assessment of pain using VAS. |
Control group (without TMD) evaluated according to the Fonseca Anamnestic Index. Palpation in patients with TMD, according to RDC/ TMD axis I. |
Criteria for mea-suring tempera-ture |
Temperatures were obtained in the TMJ regions of each individual. Calculations were made from the values of ∆Τ (the temperature dif-ference between the sides). The ∆Τ values varied between 0° and 0.8°C, and allowed the identification of in-dividuals with TMD. |
The masseter and anterior tem-poral muscles were divided into 15 facial ROIs on each side. All images showed a palette of 85 to 100 colors, with a thermal window of 0.15°C for each co-lor. Thermal sensitivity of 0.51 °C per color tone was used, based on a colorimetric scale. To cor-relate pressure pain threshold values with temperature values, thermograms were digitally su-perimposed on digital photogra-phs. |
The temperatures of the mas-seter and anterior temporal muscles were compared bet-ween the groups with and without TMD. Temperature asymmetry was determined by subtracting the temperatu-res on both sides. Temperature measurement was performed by a single evaluator, blind to allocation of the groups. The temperatures were also correlated with pain intensity. |
The infrared camera reading was interpreted by using a nor-malized (dimensionless) tem-perature, so that there was no interference from the ambient and body temperatures in the readings taken on the face. |
Using mean temperature values, patients with and without TMD were compa-red. Considering the clinical va-riability and asymmetry of patients affected by TMD, the absolute mean values of temperature and pain in-tensity on the right and left sides were subtracted from each other. Facial thermal asymmetry was classified for values higher than 0.4°C and for differences in pain level higher than 1. |
Criteria for mea-suring OFP in-tensity |
1 Assessment of muscle pain or dis-comfort was classified using the fol-lowing scale: 0 = absence of pain = mild discomfort = moderate discomfort = severe discomfort Assessment of joint pain or discom-fort was classified using the follo-wing scale: = absence of pain or discomfort = mild discomfort = moderate discomfort = severe discomfort |
The VAS 100 mm long was used, with end points defined as “no pain” (left) and “worst pain ima-ginable” (right). Patients were instructed to mark the intensity of pain on this scale. All volun-teers were asymptomatic on the day of the exam (VAS = 0). |
The VAS was used, with the following classification: 0 = absence of pain From 1 to 2 = mild pain From 3 to 4 = moderate pain 5 or more = intense pain |
The VAS was used for mea-suring pain. All volunteers were asymptomatic on the day of the exam (VAS = 0). |
A NRS was used to assess the intensity of pain on pal-pation, with the following scores: 0 = No pain = mild pain = moderate pain = Intense pain The absolute mean tem-peratures were correlated with the pain scores on pal-pation of axis I of the RDC/ TMD, for each ROI. |
Results |
Control group with a high level of ther-mal symmetry in the TMJ region. Group of symptomatic patients with low level of thermal symmetry. Since there was a correlation between the temperatures obtained at different points, the temperature analysis was limited to areas of the TMJ only. When TMJ ∆Τ val-ues were equal to or greater than 0.3°C, the subject was classified as having TMD. The results indicated that as the level of pain in the TMJ increased, the mean TMJ ∆Τ values also increased. Signifi-cant differences were found between individuals without joint pain (11 cases) and individuals who reported mild dis-comfort on palpation (8 cases), moder-ate discomfort on palpation (8 cases) and severe discomfort on palpation (17 cases). The results of the muscle pain assess-ments showed no significant differences in temperature between individuals with and without mild muscle pain. However, individuals with moderate and severe muscle pain demonstrated sig-nificant differences in temperature when compared to individuals with no pain or only mild muscle pain. |
The pressure threshold for trigger points was lower in referred pain points than in local pain points. The masseter muscle showed great-er sensitivity to pain than the tempo-ral muscle. The temporal muscle was signifi-cantly more hyperthermic than the masseter. Moderately significant correlations were observed between pressure and temperature values, suggesting that the greater the force applied, the higher was the local temperature re-corded. Furthermore, temperatures at the local pain points were higher than they were in the areas of re-ferred pain. The areas of the face that were most heated were correlated with regions without trigger points (above 34°C). At the same time, values below 33°C were related to referred pain. There-fore, the temperature decreased ac-cording to the severity of myofascial dysfunction. |
No significant correlations were found between pain in-tensity and skin temperature in the region of the masseter and anterior temporal mus-cles. No significant difference in skin temperature was found between individuals with and without TMD. |
Infrared imaging revealed a 1.4°C difference between the mean temperatures of the an-terior temporal and masseter muscles, indicating that the temporal muscle was signifi-cantly more hyperradiant than the masseter. Temperatures in the regions of the masseter and anterior temporal muscles in patients with myogenic TMD were significantly lower than those measured in volunteers in the control group. The affected muscle region presented a lower temperature than the corresponding unaf-fected area, that is, temperatu-res decreased with the severity of myogenic TMD. |
The values defined by IT showed a low level of ac-curacy for diagnosis. A negative correlation was found between pain intensity and temperatu-re in the region of the left middle masseter and left inferior masseter muscles, showing that as the pain increased, the local tem-perature decreased. No asymmetry between temperature or pain was found in the regions evaluated in patients with TMD. |
Conclusion |
The findings of this study provided addi-tional evidence relative to the clinical use of IT as an objective examination for the purpose of including or ruling out TMD as a cause of OFP, thus avoiding unne-cessary TMD treatments. The region of the TMJ of patients with TMD and pain was hotter than the same area of individuals without TMD and those who were not in pain. IT showed promise as a tool to distin-guish individuals with and without TMD, with sensitivity of 92%, specificity of 85% and accuracy of 89%. |
The greater the force applied, the higher is the local temperature recorded. Temperatures at the local pain points were higher than they were in the areas of referred pain. Temperature decreased as the severity of myofascial dysfunction increased. The thermographic image of the trigger point is hyporadiant when compared to that of the region without a trigger point. IT made it possible to identify trigger points, by dividing them into local pain and referred pain. If the thermal values are used in con-junction with physical assessment, they can serve as a means of scree-ning and improving diagnostic accu-racy in clinical practice. |
The intensity of pain was not significantly associated with the temperature of skin on the masticatory muscles or asymmetries between tem-peratures. No significant differences in temperature or asymmetry were detected between in-dividuals with and without TMD. |
The temperature of areas of the masseter and anterior temporal muscles decreases in the presence of myogenic TMD, suggesting that IT may be useful in the assessment of myogenic TMD. Moreover, it can be used as a clinical screening method for impro-ving diagnostic accuracy. |
IT did not produce results that could satisfactorily contribute to the differen-tial diagnosis between in-dividuals with and without TMD The increase in pain in-tensity on palpation in patients with TMD was accompanied by a reduc-tion in local temperature in some of the regions evaluated. |