Coordination in oro-pharyngeal biomechanics during human swallowing.

In swallowing, the tongue contacts against the hard palate to generate pressure for propelling a bolus from the oral cavity into the pharynx. Meanwhile, the hyoid and larynx move upward and forward to facilitate the bolus from the pharynx into the esophagus. It has been well known that sequential coordination between those actions is critical for safety accomplishment of swallowing. However, the absence of noninvasive assessment for it limits the detection to the physiological symptom of dysphagia. We applied a sensor sheet on the hard palate to measure tongue contact pressure and a bend sensor on the frontal neck to monitor the laryngeal movement, which was synchronized with hyoid motion for assessing the coordination between both actions in 14 healthy male subjects when swallowing 5ml of water. The sequential order of tongue pressure and hyoid movement was successfully displayed. Tongue pressure was produced after slight movement of the hyoid and closely to the hyoid elevation, then reached a maximum when the hyoid stabilized in the most anterior-superior position, and ceased concurrently with the onset of hyoid descent. Additionally, the synchronized data from both sensors showed positive correlations between identified time points on the laryngeal signal waveform and onset, peak and offset of tongue pressure. Our sensing system successfully showed the coordination between tongue pressure production and hyoid motion, and could be a simple and noninvasive method for clinicians to evaluate the oral and pharyngeal stages of swallowing.

Effect of complete denture wearing on tongue motor biomechanics during swallowing in edentulous older adults.

AIM: Contact of the tongue against the hard palate plays an important role in swallowing. Therefore, age-related decline in tongue function has received much attention. The purpose of the present study was to investigate the effect of complete denture wearing on tongue motor biomechanics during swallowing in healthy edentulous older adults. METHODS: A total of 19 edentulous patients (6 males and 13 females, mean age 76.2 ± 7.2 years) without any history of neuromuscular disease or dysphagia were selected. All patients were wearing complete dentures in both the upper and lower jaws. Tongue pressure against the hard palate during swallowing saliva was recorded using an original T-shaped sensor sheet with five measuring points. Measurements were carried out both with and without the prostheses. For evaluating swallowing ability, the frequency of swallowing saliva in 30 s was recorded (Repetitive Saliva Swallowing Test). RESULTS: With the prostheses, the maximal magnitude and duration of tongue pressure was larger at Ch. 1 (anterior-median part of the hard palate) and Ch. 2 (mid-median part) right and left circumferential parts than without the prostheses. As for the integral of tongue pressure, that with prostheses was larger at all 5 channels than that without prostheses. There was significant improvement in the Repetitive Saliva Swallowing Test value while wearing prostheses. CONCLUSIONS: These results suggested that swallowing function deteriorated as a result of the decline in tongue-palate contact on removing complete dentures in edentulous older adults. CLINICAL RELEVANCE: The present study showed the effect of wearing prostheses on swallowing in edentulous older adults.

Tongue pressure during swallowing is decreased in patients with Duchenne muscular dystrophy.

Although dysphagia is a life-threatening problem in patients with Duchenne muscular dystrophy (DMD), the pathophysiology of oral stage dysphagia is yet to be understood. The present study investigated the tongue motor deficit during swallowing in patients with DMD and its relationship with disease-specific palatal morphology. Tongue pressure during swallowing water was recorded in 11 male patients with DMD and 11 age- and sex-matched healthy subjects using an intra-oral sensor with five measuring points, and the state of tongue pressure production was compared between the groups. Palatal morphology was assessed by a non-contact three-dimensional scanner on maxillary plaster models. In patients with DMD, the normal sequential order of tongue-palate contact was lost and the maximal magnitude and integrated value of tongue pressure on the mid-anterior part of palate were smaller than those in healthy subjects. The width of the palate in patients was greater than that in healthy subjects and the depth of the palate in patients had a negative correlation with tongue pressure magnitude on the median palate. Our results suggested that the deteriorated tongue motor kinetics prevented tongue movement during swallowing that was appropriate for the depth of the palate and affects the state of tongue pressure production during swallowing.

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.