Piancino Maria Grazia, Bracco Pietro, Vallelonga Teresa, Merlo Andrea, Farina Dario
University of Turin, Department of Orthodontic and Gnathology-Masticatory Function, Italy.
J Electromyogr Kinesiol. 2008 Dec;18(6):931-7. doi: 10.1016/j.jelekin.2007.05.006. Epub 2007 Jul 5.
The aim of the study was to evaluate the effect of bolus hardness on the kinematic of mastication and jaw-elevator muscle activity in subjects with normal dental occlusion and function. The mandibular motion and the surface EMG envelope of the masseter and temporalis anterior muscles were assessed in twelve subjects during mastication of a soft and hard bolus of the same size. When chewing the hard bolus, the chewing pattern in the frontal plane was significantly higher and wider, with smaller closure angle and higher peak velocity than when chewing the soft bolus. EMG peak amplitude of both the masseter and anterior temporalis muscles was higher for the side of the bolus but the contralateral side increased its activity significantly more than the ipsilateral side when the hardness of the bolus increased (for the masseter, mean+/-SD: 130.4+/-108.1% increase for the contralateral side and 29.6+/-26.9% for the ipsilateral side). Moreover, the peak EMG activity for both muscles occurred more distant from the closure point with hard bolus. The increased activity of the contralateral side may help maintaining the mandibular equilibrium, with indirect participation to the power stroke generated by the chewing-side masseter. The results provide kinematic and EMG adaptations to bolus hardness in healthy subjects and can be used as normative data in the development of methods for early diagnosis of impaired chewing function.
本研究的目的是评估团块硬度对牙合与功能正常的受试者咀嚼运动学及升颌肌活动的影响。在12名受试者咀嚼相同大小的软质和硬质团块时，评估其下颌运动以及咬肌和颞肌前肌的表面肌电图包络。咀嚼硬质团块时，额面的咀嚼模式显著更高、更宽，闭合角度更小，峰值速度比咀嚼软质团块时更高。团块侧咬肌和颞肌前肌的肌电图峰值幅度更高，但当团块硬度增加时，对侧的活动显著比同侧增加更多（咬肌：对侧平均增加±标准差为130.4±108.1%，同侧为29.6±26.9%）。此外，两种肌肉的肌电图峰值活动在咀嚼硬质团块时离闭合点更远。对侧活动增加可能有助于维持下颌平衡，间接参与咀嚼侧咬肌产生的动力冲程。这些结果提供了健康受试者对团块硬度的运动学和肌电图适应性，可作为咀嚼功能受损早期诊断方法开发中的标准数据。
