Changes in Masticatory Muscle Activity Over Time by Facial Skin Temperature Area During Gum Chewing

Aim: The purpose of this study was to quantify the change in facial skin temperature during mastication, and analyze the two aspects of habitual masticatory side and masticatory ability, and to clarify the change of masticatory muscle activity over time. Method: Subjects were 23 healthy women (21.3±0.4 years old). An infrared thermography camera was used to measure the left and right facial skin temperatures at rest and when chewing gum. The subjects were given dental xylitol gum and freely chewed it at a rate of once per second for 15 minutes. Skin temperature was measured 5, 10, and 15 minutes after the start of chewing. The facial reference area was measured between 30 to 36°C with a resolution of 1°C per pixel. The habitual masticatory side was determined by the stopping method, and from the 2 minute rest facial skin temperature area of the habitual non-masticatory side, and two groups were formed according to chewing strength. Results: There were 13 subjects in the weak chewing group and 10 in the strong group, with no significant difference in age, height, weight, BMI, and body fat percentage. The skin temperature increased with chewing, but the increase was less on the habitual non-masticatory side than on the masticatory side. Although there was no difference in muscle activity between the habitual masticatory side of the strong and weak chewing group, the muscle activity on the non-masticatory side was less than on the habitual masticatory side in the weak chewing group. Conclusions: The amount of masticatory muscle activity at rest was classed as either strong or weak chewing ability, and muscle activity was examined on both the habitual masticatory side and the habitual non-masticatory side. This significant difference suggests that using thermography was useful for determining masticatory ability on the chewing muscle activity at rest. Furthermore, being able to determine muscle activity by measuring changes in the skin temperature area by thermography, suggests that the method used in this study was viable.