Analysis of masseter muscle oxygenation and mandibular movement during experimental gum chewing with different hardness

Abstract

Objective. The purpose of this study was to analyze masseter muscle oxygenation changes and mandibular movements in the experimental chewing of gums with different hardness. Material and Methods. Subjects for this experiment comprised 23 male volunteers with normal occlusion. Mean age (SD) was 28.3 (2.2) years. Three kinds of gum with mean fracture stresses of 3.52×10⁴ N/m² (Gum 1), 5.35×10⁴ N/m² (Gum 2), and 14.0×10⁴ N/m² (Gum 3) were used. The subjects were instructed to chew gum for 80 s (100 strokes) on the voluntary chewing side at a pace of 1.25 strokes/s. Oxygen saturation in the masseter muscle and mandibular movement during gum chewing were recorded simultaneously using near-infrared spectroscopy tissue oximetry and mandibular kinesiography. Results. For Gum 1, no subjects showed any significant changes in oxygen saturation during gum chewing. For Gum 2, 10 subjects showed no significant changes, whereas the other 13 showed significant decreases in oxygen saturation. For Gum 3, significant decreases were seen in all subjects. Chewing motions were larger and velocity was higher in gum chewing with decreases in masseter muscle oxygen saturation compared to chewing showing no significant changes. Conclusions. The results suggest that the harder texture of gum enlarges chewing motion and increases chewing velocity, with an increase in the contribution of anaerobic metabolism to energy yield in masseter muscle. Differences in the responses to gum hardness may indicate individual differences in muscle fatigue tendencies when chewing harder foods.