Department of Orthodontics and Pediatric Dentistry, School of Dentistry, University of Michigan, Ann Arbor, MI 48109-1078, USA.
Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI 48109-1078, USA.
Arch Oral Biol. 2017 Nov;83:161-168. doi: 10.1016/j.archoralbio.2017.07.020. Epub 2017 Jul 29.
Mastication consists of rhythmic jaw openings and closings. Recent studies suggest that muscle mechanical properties determine the rhythmic rate; however, speed-accuracy tradeoffs may also play a role. This study evaluated how variation in chewing rate affected chewing performance, how masticatory muscle activity varied with chewing rate, and whether morphology and demographics contributed to performance.
Chewing performance and muscle activity were sampled in 23 healthy, fully-dentate adults, who chewed a standardized test food to a metronome set at 0.5, 0.75, 1, 2 and 3 times their 'natural' chewing rates. Subjects produced ten chews per trial, and five trials for each of the five rates. Surface electromyographic (EMG) activity was sampled from masseter and temporalis muscles bilaterally. Demographic, occlusal, and cephalometric data were also obtained.
Chewing performance, defined by median particle size, was inversely related to chewing rate; however, performance was not remarkably improved at rates slower than the natural chewing rate. Above the natural chewing rate, variability in EMG bursts diminished, suggesting a reduction in muscle activity modulation at fast rates. Occlusal contacts and most morphological features appeared to play a limited or no role in performance.
Results support the hypothesis that the 'natural' chewing rate is selected to be as fast as possible while providing sufficient time to allow EMG modulation for improved performance. The interplay between EMG modulation and individual variation in skeletal morphology is likely critical for optimal chewing performance.
咀嚼由有节奏的下颌开口和闭合组成。最近的研究表明，肌肉机械特性决定了有节奏的速率；然而，速度-准确性权衡也可能起作用。本研究评估了咀嚼速度的变化如何影响咀嚼性能，咀嚼肌活动如何随咀嚼速度而变化，以及形态和人口统计学因素是否对性能有贡献。
在 23 名健康、完全有牙的成年人中采样咀嚼性能和肌肉活动，他们根据节拍器以 0.5、0.75、1、2 和 3 倍于“自然”咀嚼速度咀嚼标准化测试食品。每个试验受试者产生 10 次咀嚼，每个速率进行 5 次试验。从双侧咬肌和颞肌采集表面肌电图（EMG）活动。还获得了人口统计学、咬合和头影测量数据。
以中值粒径定义的咀嚼性能与咀嚼速度呈反比；然而，在低于自然咀嚼速度的速度下，性能并没有显著提高。在自然咀嚼速度以上，肌电爆发的可变性减小，表明在快速率下肌肉活动调制减少。咬合接触和大多数形态特征似乎在性能方面的作用有限或没有。
结果支持这样的假设，即“自然”咀嚼速度被选择为尽可能快，同时提供足够的时间允许 EMG 调制以提高性能。EMG 调制和骨骼形态个体差异之间的相互作用可能对最佳咀嚼性能至关重要。
