Evaluation of subjective toughness feeling of the foods for efficient masticatory muscle activity in daily mastication for occlusal stability

In order to evaluate the effectiveness of daily mastication for occlusal stability, the relationship between the subjective masticatory feeling and electromyogram (EMG) activity was examined. Seventeen female volunteers aged 20.5 +/- 1.0 years and nine test foodstuffs were selected. Five kinds of food texture, i.e., hardness, cohesiveness, springiness, gumminess, and chewiness, were measured and calculated in each test foodstuff. Electromyograms were measured while subjects ate to evaluate masticatory muscle activity during chewing the foodstuffs up to swallowing. Correlations between the mechanical property of the foodstuffs and the EMG parameters were examined. For each of the five properties, subjects were divided into those having high (top 8) or low (low 8) correlations between the score for subjective feeling of toughness and the food property. Significant positive correlations were found between masticatory muscle activity or the total mastication time and the score for subjective feeling of toughness. The top 8 group in "hardness" had significantly longer chewing cycle times, and the top 8 group in "cohesiveness" had significantly higher total masticatory muscle activity and longer total mastication time. There are different features of EMG parameters between the top 8 in "hardness" and "cohesiveness". These findings suggest that the subjective feeling of toughness influences effective daily mastication, and that recognition of the subjective feeling of toughness would be useful in masticatory training for occlusal stability. (C) 2009 Elsevier Ltd and the Japanese Orthodontic Society. All rights reserved.