Evaluation of Tongue-, Jaw-, and Swallowing-Related Muscle Coordination During Voluntarily Triggered Swallowing

Purpose: The prosthodontic treatment of dysphagic patients may preclude favorable treatment outcomes due to uncoordinated or discordant oral and pharyngeal functions. Since optimal treatment requires a full understanding of the mechanism of oropharyngeal swallowing, this study seeks to describe the normal temporal pattern of tongue-, jaw-, and swallowing-related muscle coordination during voluntarily triggered swallows in healthy patients. Materials and Methods: Tongue pressure against the hard palate at seven measuring points, swallowing sounds, and surface electromyography (EMG) activity of the masseter, anterior digastric, and infrahyoid muscles during voluntarily triggered swallowing were recorded in seven healthy male volunteers. The order of onset and offset of these parameters was analyzed by repeated-measures two-way analysis of variance. Results: The onset of anterior digastric muscle activity occurred first and was significantly earlier than the onset of the masseter or infrahyoid muscles and tongue pressure. The onset of masseter muscle activity was also significantly earlier than that of the infrahyoid muscle and tongue pressure. Offset of masseter activity was almost simultaneous with the swallowing sound and was significantly earlier than the offset of the anterior digastric and infrahyoid muscles as well as tongue pressure. The EMG burst of the anterior digastric muscle continued until the offset of tongue pressure, and was followed by the offset of infrahyoid muscle activity. Conclusions: The temporal coordination patterns of the tongue, jaw, and oropharyngeal muscles during voluntarily triggered swallowing appear to agree with known safe management of a bolus and offer criteria for evaluating the function of oropharyngeal swallowing.