Intramuscular and skin surface temperatures of the resting human superficial masseter muscle

The intramuscular and skin surface temperature of the central part of the superficial masseter muscle was measured with thermocouples in 25 individuals with none or mild signs of craniomandibular disorders. The intramuscular temperature averaged 35.7 degrees C, varying between 34.6 and 36.5 degrees C. The average difference between the right and left sides was 0.4 degrees C. The skin surface temperature averaged 33.2 degrees C, varying between 31.1 and 35.4 degrees C. The average difference between sides for this temperature was also 0.4 degrees C. The correlation between intramuscular and skin surface temperature was weak, and the average difference was 2.5 degrees C, with a range from 0.4 to 4.6 degrees C. The spatial variation in skin surface temperature 5 mm around the central measuring point was small. The reproducibility of both intramuscular and skin surface measurements, as assessed by the standard deviation for a single measurement, was acceptable.