Role of tongue pressure production in oropharyngeal swallow biomechanics

Effect of carbonation and thickening on voluntary swallow in healthy humans

BACKGROUND

Liquid modification is a widely established strategy of treatment for patients with dysphagia. The modification of liquid particularly by thickening or carbonation is a common approach to promote safe swallowing.

OBJECTIVE

This study sought to investigate how carbonated and/or thickened water modulates swallowing behaviours during swallowing in healthy young individuals.

METHODS

Thirty-one healthy volunteers (9 men, 22 women; mean age ± standard deviation [SD], 25.7 ± 6.2 years) were instructed to swallow 20 mL of water, carbonated water and carbonated juice with and without added thickening agent. Electromyograms (EMGs) of the suprahyoid (S-hyo) muscles were recorded to evaluate swallowing behaviours. Obtained S-hyo EMG bursts was analysed using the following outcome parameters: onset latency, the time between swallowing que to onset of EMG burst; rising time and falling time, defined as the time between onset and peak, and between peak and offset, respectively; duration, defined as the time between onset and offset of EMG burst; and area integral value under the waveform.

RESULTS

Effects of thickening demonstrated the extended onset latency, EMG burst duration including falling time and the larger area of EMG in thickened liquid compared to thin liquid, but there was not much difference between thin and thickened carbonated liquids. Carbonation significantly decreased the duration including falling time for thickened but not for thin liquids.

CONCLUSION

Patients with dysphagia can benefit from use of carbonated or thickened water while the effects on swallowing physiology may differ between carbonation and thickening.

Effects of tongue strengthening exercises in healthy adults and elderly: an integrative literature review

PURPOSE

To summarize and discuss the scientific literature on the effects of tongue strengthening exercises on healthy adults and elderly people.

RESEARCH STRATEGIES

We searched two online databases, PubMed and Web of Science.

SELECTION CRITERIA

Studies with evidence of interventions in tongues strengthening exercises in healthy individuals over 18 years of age.

DATA ANALYSIS

Study objectives, design, participants, interventions, gain in the percentage of tongue strength.

RESULTS

Sixteen studies were included. There was an increase in tongue strength after strengthening training in healthy adults and elderly people. This strength was maintained after a short period of detraining. We could not compare the results between age groups due to the different methodological designs. We found that the approach of a less intense training protocol was more effective in gaining tongue strength in the elderly.

CONCLUSION

Tongue strength training proved effective in increasing tongue strength in healthy individuals of different age groups. The benefits reported for the elderly corresponded to the reversal of the progressive loss of strength and muscle mass caused by aging. These findings must be interpreted with caution considering the number of studies on the elderly and their methodological variability.

In situ quantitative assessment of food oral processing parameters: A review of feasible techniques and devices

Oral processing is a combination of various actions, the detailed description of which has always been the subject of relevant research. By means of imaging technology and sensory evaluation, more knowledge of oral processing have been accumulated. Presently, the advances in sensory technology have added quantitative parameters to the qualitative description of oral processing, which also enriched the specifics of each action. Previous studies have shown that oral processing includes lip closure, dental occlusion, masticatory muscles activity, tongue movement, and swallowing, whose processing contains rich information such as the movement of organ and the intensity of organ contacts. "Quantification" was taken in this review as the basic feature of in situ detection information, the relevant parameters and feasible methods for the quantitative description of each activity was recorded in detail. In addition, basic problems and feasible optimization schemes of the existing in situ detection device are also proposed in the hope of promoting the development of in situ detection device thus providing available information for the description of oral processing.

Quantification of the Swallowing Mechanism Through Muscle Synergy Analysis

Decreased swallowing function increases the risk of choking and aspiration pneumonia. Videofluoroscopy and computed tomography allow for detailed observation of the swallowing movements but have radiation risks. Therefore, we developed a method using surface electromyography (sEMG) to noninvasively assess swallowing function without radiation exposure. A 44-channel flexible sEMG sensor was used to measure the sEMG signals of the hyoid muscles during swallowing in 14 healthy young adult and 14 elderly subjects. Muscle synergy analysis was performed to extract the muscle synergies from the sEMG signals, and the three synergies were extracted from the hyoid muscle activities during the swallowing experiments. The experimental results showed that the three synergies represent the oral, early pharyngeal, and late pharyngeal swallowing phases and that swallowing strength is tuned by the strength of the muscle activities, whereas swallowing volume is controlled by adjusting muscle activation timing. In addition, the timing of the swallowing reflex is slower in elderly individuals. The results confirm that the proposed approach successfully quantifies swallowing function from sEMG signals, mapping the signals to the swallowing phases.

Association between Tongue Pressure and Jaw-Opening Force in Older Adults

Tongue pressure (TP) is used to assess tongue muscle strength and is related to function and frailty. While performing TP, it is necessary to elevate the tongue and oral floor by contracting the suprahyoid muscles. However, the association between TP and suprahyoid muscle strength remains unclear. Accordingly, this study investigated the relationship between TP and jaw-opening force (JOF), an indicator of suprahyoid muscle strength. This cross-sectional study included 88 independent community-dwelling participants aged ≥65 years. Age, sex, and the number of remaining teeth were recorded. Ultrasonography was used to evaluate the cross-sectional area of the tongue and geniohyoid muscle, as representatives of the suprahyoid muscles. Sarcopenia was diagnosed based on appendicular skeletal muscle mass index, handgrip strength, and gait speed. Multiple regression analysis was performed with TP as the dependent variable. TP was significantly associated with JOF (β = 0.371, p = 0.003). This study revealed that decreased TP was associated with a decline in JOF and suprahyoid muscle mass in older adults. Thus, low TP may be associated with decreased JOF. Prevention of the weakness of the suprahyoid muscles and maintaining TP may also contribute to the prevention of frailty associated with TP.

Recovery pattern analysis of swallowing function in patients undergoing total glossectomy and hemiglossectomy

OBJECTIVES

To investigate the recovery process of swallowing function and ascertain swallowing pattern in patients undergoing total glossectomy (TG).

MATERIALS AND METHODS

A cohort study was conducted in consecutive patients with tongue squamous cell carcinoma who received TG/hemiglossectomy (HG) from May 2017 to December 2019. Exposure factors included tongue resection range (HG and TG) and postoperative radiotherapy (PRT and non-PRT). The swallowing functions were evaluated by M.D. Anderson dysphagia inventory (MDADI), water swallow test (WST), and tongue pressure (TP) at pretreatment, 1, 4, 7, 12, 18 and 24 months postoperatively. Videofluoroscopy swallowing study (VFSS) was applied to analyze swallowing pattern of TG patients.

RESULTS

A total of 67 patients were enrolled, of which 17 underwent TG and 50 underwent HG. Both MDADI and TP of the TG and PRT group were lower than those of the HG and non-PRT group. TG patients had no evident improvement in MDADI and TP after surgery. There was a higher risk of swallowing unsafety with abnormal WST outcome in TG (P < 0.001, OR = 106.52) than that in HG. VFSS analysis identified prolonged oral and pharyngeal transit time, disorganized swallowing sequence, abnormal hyoid bone movement, and frequent invalid swallows in patients with TG. A shortened OTT (<5066.50 ms) and a larger pharyngeal constriction ratio (PCR > 0.31) were associated with increased risks of penetration and aspiration.

CONCLUSION

Postoperative swallowing pattern is a characteristic of severely impaired safety and efficacy in patients with TG. Impaired OTT and PCR are variables that should be examined when determining the need for rehabilitation treatment.

Effects of Tongue-Strengthening Exercise on Tongue Strength and Effortful Swallowing Pressure in Young Healthy Adults: A Pilot Study

PURPOSE

The purpose of this study was to investigate the effects of tongue-strengthening exercise (TSE) on tongue strength and effortful swallowing pressure in young healthy adults.

METHOD

Thirteen young healthy volunteers (six men, seven women; M _age = 20.5 ± 0.5 years) performed 8 weeks of isometric TSE 3 days per week. A tongue pressure measurement device was used to measure maximum isometric tongue pressure (MITP) and conduct the TSE, and a tactile sensor system attached to the hard palate was used to measure effortful swallowing pressure. MITP and effortful swallowing pressure were measured at baseline, after 4 and 8 weeks of training, and at 4 and 8 weeks after the last training session to examine the detraining effects.

RESULTS

The results indicated that both MITP and effortful swallowing pressure increased significantly from baseline to 8 weeks after training. Although the improved MITP significantly decreased at 4 and 8 weeks after training cessation, no detraining effect was observed for effortful swallowing pressure.

CONCLUSIONS

TSE is an effective method for increasing tongue pressure in wide tongue-palate contact areas during effortful swallow. The effortful swallowing pressure gained with TSE appears to be maintained for at least eight nontraining weeks.

Clarification of the aspects of tongue-palate contacts during mastication with/without stage II transport

BACKGROUND

During mastication, the tongue presses the bolus into the pharynx by a "squeeze-back" motion, known as stage II transport (St2Tr). However, the pressure of St2Tr tongue-palate contact has not been examined.

OBJECTIVES

We aimed to clarify aspects of St2Tr occurrence and tongue-palate contact during mastication by measuring tongue pressure.

METHODS

Ten healthy adults (eight men, two women, aged 26.8 ± 2.2 years) were enrolled. Tongue pressure was measured (Swallow Scan) during mastication. Sensors were placed on the palate near the incisive papilla (Ch.1), in the middle (Ch.2), at the posterior (Ch.3), and near the first molars on the habitual (Ch.H) and non-habitual (Ch.Nh) masticatory sides. Nasopharyngeal endoscopy confirmed St2Tr and swallowing. Tongue pressures were measured repeatedly, from mastication onset through the first swallow, until eight sets of data were obtained. Tongue-palate contact frequencies, integrated values of tongue pressure, and mastication times were recorded for St2Tr(+) and St2Tr(-) mastication conditions.

RESULTS

St2Tr occurred in 43 of 80 trials (53.8%). St2Tr(+) exhibited the highest tongue-palate contact frequency at Ch.H; it exhibited higher contact frequencies at Ch.2, Ch.3 and Ch.H than St2Tr(-). St2Tr(+) exhibited higher tongue pressures at Ch.1, Ch.2 and Ch.H than at Ch.3; it exhibited higher tongue pressures at Ch.1 and Ch.2 than St2Tr(-).

CONCLUSION

The study suggested that during St2Tr, the tongue frequently touched the palate at the central and posterior regions, as well as at its habitual masticatory side. It applies the strongest pressure at the anterior and central palate to transport the bolus to the pharynx.

Modulation of tongue motion and tongue pressure during liquid swallowing with different bolus volumes

BACKGROUND

The tongue functions by modulating according to bolus volume when swallowing; however, associated tongue dynamics are unclear.

OBJECTIVE

We aimed to clarify how tongue motion and tongue pressure change with bolus volume during swallowing.

METHODS

Sixteen healthy volunteers (age 29.5 ± 3.8 years; 12 males, 4 females) were recruited. Two electromagnetic articulography markers were attached, one each on the anterior and posterior parts of the tongue, to measure motion. A sensor sheet, with five pressure-sensitive points, was attached to the hard palate to measure tongue pressure. Participants were asked to swallow 3 ml and 10 ml of water. Motion trajectory, maximum velocity, vertical displacement just before contact with the hard palate, and maximum magnitude and duration of tongue pressure were analysed.

RESULTS

Tongue rotation was observed in the sagittal plane; its rate of appearance was significantly higher when swallowing 3 ml of water than when swallowing 10 ml, and the rate of rotation at posterior part was significantly higher than at the anterior part. The maximum velocity and vertical displacement were significantly greater when swallowing 10 ml of water than those when swallowing 3 ml of water. There was no significant difference in either the maximum magnitude of tongue pressure or maximum duration of tongue pressure between 3 ml and 10 ml.

CONCLUSION

Bolus volume influenced the pattern of tongue motion; however, there was no difference in tongue pressure.

Dysphagia in amyotrophic lateral sclerosis: Quantification of bulbar motor dysfunction

BACKGROUND

Dysphagia as a sequel and possible early sign of amyotrophic lateral sclerosis (ALS) is caused by progressive impaired bulbar motor function.

OBJECTIVE

To evaluate bulbar motor dysfunction in patients suffering from ALS compared to a healthy reference group.

METHODS

A clinical study and prospective group comparison was designed. Patients and healthy volunteers were examined in the outpatient clinic of our university medical center. Ten patients with ALS and 20 healthy volunteers were included. All participants underwent a flexible endoscopic evaluation of swallowing (FEES) and a manometric measurement of the maximal sub-palatal atmospheric pressure generated by suction as well as of the prevalent pressure during swallowing. Additionally, the Sydney Swallow Questionnaire (SSQ) was completed by all participants to score the self-rated extent of dysphagia.

RESULTS

Comparing maximal suction pressures, the group of patients showed significantly lower values (p < .001). There was a significant correlation between reduced pressures and the degree of dysphagia (SSQ score) (r = -0.73).

CONCLUSIONS

As the oral cavity is an easily accessible compartment of the upper digestive tract, manometric measurements might serve as a simple instrument in order to detect or to monitor bulbar motor dysfunction. Oral manometry may facilitate early detection and monitoring of dysphagia in ALS. Larger studies are required to confirm our findings.

Exploring directional and fluctuating asymmetry in the human palate during growth

Objectives

Palate morphology is constantly changing throughout an individual's lifespan, yet its asymmetry during growth is still little understood. In this research, we focus on the study of palate morphology by using 3D geometric morphometric approaches to observe changes at different stages of life, and to quantify the impact of directional and fluctuating asymmetry on different areas at different growth stages.

Materials and Methods

The sample consists of 183 individuals (1–72 years) from two identified human skeletal collections of 19th and early 20th Century Italian contexts. A 3D‐template of 41 (semi)landmarks was applied on digital palate models to observe morphological variation during growth.

Results

Asymmetrical components of the morphological structure appears multidirectional on the entire palate surface in individuals <2 years old and become oriented (opposite bilateral direction) between 2 and 6 years of age. Specifically, directional asymmetry differentially impacts palate morphology at different stages of growth. Both the anterior and posterior palate are affected by mild alterations in the first year of life, while between 2 and 6 years asymmetry is segregated in the anterior area, and moderate asymmetry affects the entire palatal surface up to 12 years of age. Our results show that stability of the masticatory system seems to be reached around 13–35 years first by females and then males. From 36 years on both sexes show similar asymmetry on the anterior area. Regarding fluctuating asymmetry, inter‐individual variability is mostly visible up to 12 years of age, after which only directional trends can be clearly observed at a group level.

Discussion

Morphological structure appears instable during the first year of life and acquires an opposite asymmetric bilateral direction between 2 and 6 years of age. This condition has been also documented in adults; when paired with vertical alteration, anterior/posterior asymmetry seems to characterize palate morphology, which is probably due to mechanical factors during the lifespan. Fluctuating asymmetry is predominant in the first period of life due to a plausible relationship with the strength of morphological instability of the masticatory system. Directional asymmetry, on the other hand, shows that the patterning of group‐level morphological change might be explained as a functional response to differential inputs (physiological forces, nutritive and non‐nutritive habits, para‐masticatory activity as well as the development of speech) in different growth stages. This research has implications with respect to medical and evolutionary fields. In medicine, palate morphology should be considered when planning orthodontic and surgical procedures as it could affect the outcome. As far as an evolutionary perspective is concerned the dominance of directional asymmetries in the masticatory system could provide information on dietary and cultural habits as well as pathological conditions in our ancestors.

Noninvasive Measurement of Tongue Pressure and Its Correlation with Swallowing and Respiration

Tongue pressure plays a critical role in the oral and pharyngeal stages of swallowing, contributing considerably to bolus formation and manipulation as well as to safe transporting of food from the mouth to the stomach. Smooth swallowing relies not only on effective coordination of respiration and pharynx motions but also on sufficient tongue pressure. Conventional methods of measuring tongue pressure involve attaching a pressure sheet to the hard palate to monitor the force exerted by the tongue tip against the hard palate. In this study, an air bulb was inserted in the anterior oral cavity to monitor the pressure exerted by the extrinsic and intrinsic muscles of the tongue. The air bulb was integrated into a noninvasive, multisensor approach to evaluate the correlation of the tongue pressure with other swallowing responses, such as respiratory nasal flow, submental muscle movement, and thyroid cartilage excursion. An autodetection program was implemented for the automatic identification of swallowing patterns and parameters from each sensor. The experimental results indicated that the proposed method is sensitive in measuring the tongue pressure, and the tongue pressure was found to have a strong positive correlation with the submental muscle movement during swallowing.

Electrical Characterization of the Tongue and the Soft Palate Using Lumped-Element Model for Intraoral Neuromodulation

Intraoral functions are results of complex and well-orchestrated sensorimotor loop operations, and therefore vulnerable to small functional or neural defects. To secure the vital intraoral functions, it is important to find a way to favorably intervene the intraoral sensorimotor loop operations. The tongue and the soft palate are heavily associated with intraoral sensorimotor loops, with their dense neural innervations and occupancy of intraoral space. Therefore, electrical stimulation onto the tongue and the soft palate has a great potential to solve the problems in the intraoral functions. However, the electrical interface for both of them have not been characterized yet as a lumped-element model, for designing electrical stimulation and analyzing its effect. In this study, we measured stimulation thresholds to evoke electrotactile feedback and characterized electrical impedance across electrodes using lumped-element models. We found that average perception/discomfort thresholds for the tongue tip, lateral-inferior side of the tongue, and anterolateral side of the soft palate as 0.18/1.31, 0.37/3.99, and 1.19/7.55 mA, respectively. An R-C-R-R-C model represented the electrical interface across the tongue and the soft palate with the highest accuracy. The average component values of the R-C-R-R-C model were found as 2.72kΩ, 45.25nF, 1.27kΩ, 22.09GΩ, and 53.00nF, on average.

Increased viscosity of milk during infant feeding improves swallow safety through modifying sucking in an animal model

Infants experiencing frequent aspiration, the entry of milk into the airway, are often prescribed thickened fluids to improve swallow safety. However, research on the outcomes of thickened milk on infant feeding have been limited to documenting rates of aspiration and the rheologic properties of milk following thickening. As a result, we have little insight into the physiologic and behavioral mechanisms driving differences in performance during feeding on high viscosity milk. Understanding the physiologic and behavioral mechanisms driving variation in performance at different viscosities is especially critical, because the structures involved in feeding respond differently to sensory stimulation. We used infant pigs, a validated animal model for infant feeding, to test how the tongue, soft palate, and hyoid respond to changes in viscosity during sucking and swallowing, in addition to measuring swallow safety and bolus size. We found that the tongue exhibited substantive changes in its movements associated with thickened fluids during sucking and swallowing, but that pharyngeal transit time as well as hyoid and soft palate movements during swallowing were unaffected. This work demonstrates the integrated nature of infant feeding and that behaviors associated with sucking are more sensitive to sensorimotor feedback associated with changes in milk viscosity than those associated with the pharyngeal swallow, likely due to its reflexive nature.

Effect of fracture properties of gels on tongue pressure during different phases of squeezing and swallowing

To provide appropriate foods for elderly people with eating difficulties, it is necessary to take account of the ability of compensatory mastication such as tongue squeezing. However, the biomechanics of tongue squeezing is still unclear. The aim of present study is to investigate the effect of the initial mechanical properties of gels on the change in tongue pressure production during squeezing and swallowing. As test sample, nine kinds of gels with three fracture force and three fracture strain were prepared. Tongue pressure during squeezing and swallowing gels was measured by using an ultra-thin tongue pressure sensor with five measuring points attached on the hard palate in seven healthy participants, and analyzed at four phases; Initial squeeze, Middle squeeze, Last squeeze, and Swallowing. The maximal magnitude of tongue pressure was increased for gels with higher fracture force at most measuring points and was decreased for gels with higher fracture strain at some measuring points on the median line during Initial and Middle squeezing. However, no influence by fracture force and strain was found in magnitude during Last squeezing and Swallowing. The duration of tongue pressure increased for gels with higher force at most measuring points during Middle squeezing, although no influence by strain was found during each phase. The results clearly show how the initial fracture properties of gels influence on tongue pressure production during each phase of food oral processing, which clarified one aspect of squeezing with tongue, as the compensatory mastication.

Examining the Relationships Between Lingual Strength, Perihyoid Strength, and Swallowing Kinematics in Dysphagic Adults: A Retrospective Cross-Sectional Analysis

Purpose The aim of this study was to examine the relationships of clinical measures of lingual and perihyoid strength with displacement swallowing kinematics and swallowing safety in a heterogenous group of dysphagic adults. Method A retrospective analysis was completed of videofluoroscopic swallow studies of consecutive dysphagic outpatient adults presenting to a tertiary swallowing center from January 1, 2015, to December 31, 2017. Videofluoroscopic swallow study records were included if containing displacement swallowing kinematics of a 20-ml single liquid swallow and clinical measures of anterior (L-MIPA) or posterior (L-MIPP) lingual maximal isometric press, saliva mean swallowing pressures (S-MSP), and/or open mouth-maximal isometric press (OM-MIP). Regression analyses were used to examine the relationships between clinical measures of lingual (L-MIPA, L-MIPP, S-MSP) and perihyoid (OM-MIP) strength and displacement swallowing kinematics, and binomial logistic regressions were used to examine the relationships between clinical measures of lingual and perihyoid strength and swallowing safety (Penetration-Aspiration Scale [PAS]). Results Multivariate regressions revealed significant relationships of L-MIPA, L-MIPP, S-MSP, and OM-MIP with group-level changes to the displacement swallowing kinematics. Univariate analyses revealed significant relationships of L-MIPA and L-MIPP with pharyngeal constriction ratio, maximal extent of upper esophageal segment opening, and PAS. Conclusions Weak relationships were identified of clinical measures of lingual and perihyoid strength with displacement swallowing kinematics. These findings suggest that clinical measures of lingual and perihyoid strength do not fully explain impairments in swallowing kinematics across a heterogenous group of dysphagic patients. Weak-to-moderate relationships were identified between clinical measures of lingual strength and PAS, suggesting that they may have value in predicting functional measures of swallowing safety. Further research is needed to examine how findings may differ between specific patient populations.

Update and review of the gerodontology prospective for 2020's: Linking the interactions of oral (hypo)-functions to health vs. systemic diseases

New lines of evidence suggest that the oral-systemic medical links and oral hypo-function are progressively transcending beyond the traditional clinical signs and symptoms of oral diseases. Research into the dysbiotic microbiome, host immune/inflammatory regulations and patho-physiologic changes and subsequent adaptations through the oral-systemic measures under ageism points to pathways leading to mastication deficiency, dysphagia, signature brain activities for (neuro)-cognition circuitries, dementia and certain cancers of the digestive system as well. Therefore, the coming era of oral health-linked systemic disorders will likely reshape the future of diagnostics in oral geriatrics, treatment modalities and professional therapies in clinical disciplines. In parallel to these highlights, a recent international symposium was jointly held by the International Association of Gerontology and Geriatrics (IAGG), Japanese Society of Gerodontology (JSG), the representative of USA and Taiwan Academy of Geriatric Dentistry (TAGD) on Oct 25th, 2019. Herein, specific notes are briefly addressed and updated for a summative prospective from this symposium and the recent literature.

Effects of Neuromuscular Electrical Stimulation (NMES) Plus Upper Cervical Spine Mobilization on Forward Head Posture and Swallowing Function in Stroke Patients with Dysphagia

After a stroke, forward head posture occurs, resulting in swallowing dysfunction. Neuromuscular electrical stimulation (NMES) combined with upper cervical spine mobilization has demonstrated enhanced recovery of the swallowing function in stroke patients. This study investigated the therapeutic effects of NMES in conjunction with upper cervical mobilization in stroke patients with dysphagia. Thirty-four stroke patients were recruited (in a randomized controlled clinical trial) and divided into an experimental group (n = 17; NMES plus upper cervical spine mobilization) and a control group (n = 17; NMES plus sham mobilization). Forward head posture was measured by craniocervical flexion test (CCFT) and craniovertebral angle (CVA). Swallowing function was measured by variations in video fluoroscopic dysphagia scale (VDS) and penetration–aspiration scale (PAS) scores using the video fluoroscopic swallowing study (VFSS). All measurements were done at baseline and after four weeks of NMES plus mobilization. A significant increase was observed in CCFT, CVA, VDS (total VDS score, oral stage score, pharyngeal stage score), and PAS score in all variations in the experimental group. The CCFT, CVA, pharyngeal stage score, total VDS, and PAS score were significantly higher in the experimental group when compared to the control group. NMES plus upper cervical spine mobilization can be regarded as a promising method to improve swallowing function and forward head posture changes in stroke patients with dysphagia.

Endurance measurement of hyoid muscle activity and hyoid-laryngeal position during tongue lift movement

BACKGROUND

Tongue lift movement (TLM) is used as a therapy to improve tongue pressure against the hard palate for dysphagic patients.

OBJECTIVE

The present study aimed to characterize the time-dependent endurance changes in hyoid muscle activity and hyoid-laryngeal displacement during TLM in different ways.

METHODS

Sixteen young healthy volunteers were instructed to perform TLM at maximum effort (100%) against the anterior and posterior parts of the hard palate using a balloon-type tongue pressure instrument, followed by a 10-second recording during anterior 80% TLM, anterior 100% TLM, posterior 80% TLM and posterior 100% TLM with visual feedback. Electromyography (EMG) of suprahyoid (S-Hyo) and infrahyoid (I-Hyo) muscles and videofluorography were simultaneously recorded. To evaluate temporal changes, the recording period was divided into three substages: early, middle and late. Tongue pressure, integrated EMG (iEMG), power frequency of EMG burst and hyoid-laryngeal position were compared among the conditions (80% vs 100%, anterior vs posterior and early vs middle vs late).

RESULTS

Tongue pressure was stably maintained for 10 seconds in all conditions. S-Hyo iEMG and I-Hyo iEMG were significantly greater at 100% than at 80%, while no significant difference was observed between positions. S-Hyo iEMG and I-Hyo iEMG significantly increased at the late stage, while power frequency of EMG burst gradually decreased. Significant temporal changes in laryngeal elevation were observed only in posterior 100% TLM.

CONCLUSION

The current results suggested that isometric posterior TLM may be more useful compared with anterior TLM in clinical situations for dysphagic patients to elevate the hyolaryngeal complex.

XROMM and diceCT reveal a hydraulic mechanism of tongue base retraction in swallowing

During primate swallowing, tongue base retraction (TBR) drives the food bolus across the oropharynx towards the esophagus and flips the epiglottis over the laryngeal inlet, protecting against penetration and aspiration of food into the airway. Despite the importance of TBR for swallowing performance, the mechanics of TBR are poorly understood. Using biplanar videoradiography (XROMM) of four macaque monkeys, we tested the extrinsic muscle shortening hypothesis, which posits that shortening of the hyoglossus and styloglossus muscles pulls the tongue base posteriorly, and the muscular hydrostat or intrinsic tongue muscle hypothesis, which suggests that, because the tongue is composed of incompressible fluid, intrinsic muscle shortening increases tongue length and displaces the tongue base posteriorly. Our data falsify these hypotheses. Instead we suggest a novel hydraulic mechanism of TBR: shortening and rotation of suprahyoid muscles compresses the tongue between the hard palate, hyoid and mouth floor, squeezing the midline tongue base and food bolus back into the oropharynx. Our hydraulic mechanism is consistent with available data on human tongue swallowing kinematics. Rehabilitation for poor tongue base retraction might benefit from including suprahyoid muscle exercises during treatment.

Correlation of Temporal Parameters of Laryngeal Excursion by Using Force-Sensing Resistor Sensors with Hyoid Motion in Videofluoroscopic Swallowing Study

Small flexible force-sensing resistor (FSR) sensors can detect laryngeal excursion during swallowing, but the detected laryngeal excursion has not been correlated with videofluoroscopic swallowing study (VFSS) results. Here, we tested the correlation of temporal parameters between the laryngeal excursion recording by FSR sensor and the hyoid motion recording by VFSS under simultaneously swallowing test recordings. Swallowing measurements were recorded in a radiological suite by simultaneously using VFSS and FSR sensors to detect hyoid motion and laryngeal excursion, respectively. Volunteers sat with their head vertical to the Frankfort plane. Two FSR sensors, each for detecting thyroid cartilage excursion and thumb pressing, were placed. VFSS images and FSR sensor signals during single 5-mL barium liquid (30% wt/volume %) bolus swallowing were collected and analyzed for four swallows per participant. In total, 15 men (28.0 ± 4.1 years old); 14 women (28.4 ± 4.2 years old) were recruited. Temporal parameters between VFSS and noninvasive system demonstrated a strong correlation by Pearson's correlation analysis: in men (R = 0.953-0.999) and in women (R = 0.813-0.982), except for VT1-V1 compared with FT1-F1, which demonstrated a moderate correlation in women (R = 0.648; all p < 0.001). Only VT1-V1 and FT1-F1 in women displayed a significant difference (p = 0.001). Therefore, this is the first study to simultaneous record VFSS and noninvasive signals by FSR sensor. The correlation of temporal parameters between these two tests was strong. This finding is valuable for future applications of this noninvasive swallowing study tool.

Tongue function and swallowing in individuals with temporomandibular disorders

The tongue participates in the oral phase of swallowing by pushing the food bolus toward the oropharynx. This relationship between tongue function and swallowing is little addressed addressed in individuals with temporomandibular dysfunction (TMD).

Coordination of tongue pressure production, hyoid movement, and suprahyoid muscle activity during squeezing of gels

OBJECTIVE

The aim of this study was to evaluate tongue movement and its biomechanical effects during squeezing, one of the oral strategies for processing soft foods, by tongue pressure sensors, videofluorography, and surface electromyography.

DESIGN

Fifteen healthy men (mean age, 31.0 ± 4.1 years) without dysphagia were recruited. A 0.1-mm-thick pressure sensor sheet with five measuring points, videofluorography, and surface electromyography were used for synchronous measurements of tongue pressure, hyoid movement, and suprahyoid muscles activity, respectively, while squeezing 5 mL of gels. Amplitude, duration, area, and their sequential order during initial squeezing were analyzed. Differences in hyoid position at the onset, peak, and offset of hyoid movement were also analyzed.

RESULTS

At the beginning of initial squeezing, tongue pressure at the middle area of the hard palate, hyoid movement, and suprahyoid muscle activity appeared simultaneously, followed by tongue pressure at the anterior area and then at the posterior area. When the hyoid was in an elevated position, the amplitude of suprahyoid muscle activity and tongue pressure peaked. At the end of initial squeezing, the hyoid position at the offset of hyoid excursion was superior to that at the onset. All evaluation items of tongue pressure, hyoid movement, and suprahyoid muscle activity were modulated according to the texture of gels.

CONCLUSIONS

During initial squeezing, tongue pressure, hyoid movement, and suprahyoid muscle activity were coordinated while being modulated by the food texture. At the end of initial squeezing, the hyoid was maintained in an elevated position, which might be beneficial for subsequent squeezing.

The effect of tongue thrusting on tongue pressure production during swallowing in adult anterior open bite cases

BACKGROUND

Tongue thrusting, which often occurs during swallowing in patients with anterior open bite, is considered to show different tongue dynamics from healthy individuals, but the details are still unclear.

OBJECTIVE

This study aimed to identify the effect of tongue thrusting on tongue pressure production during swallowing in patients with anterior open bite.

METHODS

The subjects were 11 patients with an anterior open bite and 8 healthy volunteers with individual normal occlusion. The patients were divided into a tongue-thrusting group (n = 8) and a non-thrusting group (n = 3). Tongue pressures while swallowing jelly (4 mL) were recorded by a sensor sheet system with five measuring points (Chs1-5) attached to the palatal mucosa. The time sequences, maximum magnitude and duration of tongue pressure, and swallowing time of tongue pressure were analysed.

RESULTS

Tongue pressure waveforms in the tongue-thrusting group were quite diverse compared with the other two groups. The duration at the posterior-median part in the tongue-thrusting group was significantly shorter, and the maximum magnitudes at the mid-median, posterior-median and the peripheral part were also significantly lower than in the healthy group. These results suggest that the compensatory tongue thrust action by which the tongue closes the front part of the oral cavity may make it difficult to lift the tongue and transfer the bolus.

CONCLUSION

Patients with an anterior open bite and tongue thrusting at swallowing showed diversity of tongue pressure waveforms and noticeably weaker tongue pressures from mid-median to posterior-median regions than healthy individuals.

Tongue-pressure resistance training improves tongue and suprahyoid muscle functions simultaneously

Purpose

Producing tongue pressure (TP) by pushing the tongue against the palate consists of lifting the tongue muscles and elevating the floor of the mouth via suprahyoid muscle contraction. Though studies have shown that tongue-pressure resistance training (TPRT) increases tongue function, none have focused on suprahyoid muscle function enhancements. Our study aimed to verify whether TPRT improves both tongue function and hyoid movement during swallowing.

Materials and methods

Eighteen patients (mean age: 76.8±6.2 years) with presbyphagia presenting with symptoms such as coughing and choking were enrolled. All patients performed daily living activities independently. None of the participants had diseases causing dysphagia or previous oral or pharyngeal surgery. Participants were instructed to push their tongues against the palate as hard as possible with their mouths closed for 10 seconds, and then resting for 10 seconds. A set consisted of five consecutive exercise and resting periods; two sets per day were performed for a month. TP and the oral diadochokinetic rate (ODKR), measured by repetitions of the syllables /ta/ and /ka/, assessed tongue function. The extent of anterior and superior hyoid movement and parameters related to swallowing, including the penetration aspiration scale (PAS) and the normalized residue ratio scale (NRRS) in the valleculae (NRRSv) and piriform sinus (NRRSp), were evaluated based on videofluoroscopic data.

Results

The anterior (P=0.031) and superior hyoid movement (P=0.012), TP (P=0.002), ODKR/ta/ (P=0.034), ODKR/ka/ (P=0.009), and the width of the upper esophageal sphincter (P=0.001) were larger at follow-up than at baseline. NRRSp (P=0.022), PAS (P=0.016), and pharyngeal transit times (P=0.004) were smaller at follow-up than at baseline.

Conclusion

TPRT improved tongue strength, dexterity, both anterior and superior hyoid elevation, and swallowing functions. Therefore, TPRT could improve tongue function and suprahyoid muscle function simultaneously and contribute to prevention of sarcopenic dysphagia.

Tongue pressure distribution of individual normal occlusions and exploration of related factors

Background

Tongue plays an important part in oral and maxillofacial system. Measurement of tongue pressure helps to evaluate the performance of tongue movement.

Objectives

To establish a system for measuring tongue pressure against hard palate and to preliminarily explore pressure distribution of individual normal occlusions and the relationship with dental arch form.

Methods

A total of 19 volunteers of individual normal occlusions out of 189 dental students met inclusion criteria (nine males, ten females, aged 25.53 ± 0.96 years). A force‐sensing resistor device was used to measure tongue pressure at rest and functional state (swallowing). We observed tongue pressure of four channel (anterior, posterior and lateral sides of hard palate) in sitting, supine position and swallowing. We analysed pressure differences according to gender and explored correlation relationship between tongue pressure and dental arch width and length using 3D digital maxillary image.

Results

In rest, tongue pressure against hard palate increased from front to back in both sitting and supine position, without gender differences. When swallowing saliva, the pressure at lateral sides of females was found significantly higher than that of males. Bivariate correlation analysis revealed duration of swallowing was positively correlated with BMI and weight at posterior region and positively correlated with palatal length at anterior palate. The greater the dental arch width, the smaller the pressure of swallowing in the anterior and lateral region.

Conclusion

In rest, there was consistent pressure of tongue against hard palate. The pressure increased significantly during swallowing, especially in females. Tongue pressure was related to dental arch length, width, BMI and weight.

The physiological linkage between molar inclination and dental macrowear pattern

OBJECTIVES

Exact symmetry and perfect balance between opposite jaw halves, as well as between antagonistic teeth, is not frequently observed in natural masticatory systems. Research results show that asymmetry in our body, skull, and jaws is often related to genetic, epigenetic, environmental and individual ontogenetic factors. Our study aims to provide evidence for a significant link between masticatory asymmetry and occlusal contact between antagonist teeth by testing the hypothesis that tooth inclination is one of the mechanisms driving distribution of wear in masticatory phases in addition to dietary and cultural habits.

MATERIALS AND METHODS

The present work investigates the relationship between dental macrowear patterns and tooth inclinations on a sample of complete maxillary and mandibular 3D models of dental arches from 19 young and adult Yuendumu Aboriginal individuals. The analysis was carried out on first molars (M1) from all quadrants. Occlusal Fingerprint Analysis was used for the quantification of macrowear patterns, and 2D cross-sectional geometric analysis was carried out to investigate asymmetry in dental arches.

RESULTS

The asymmetry is highly variable on both arches, and it is associated with differences in the inclination of upper M1 crowns. Each molar has variable inclination (buccal/lingual) which influence tooth to tooth contact, producing greater or lesser variation in wear pattern. Interindividual variability of morphological variation of the occlusal relationship has to be considered in macrowear analysis.

DISCUSSION

Our results suggest that overall asymmetry in the masticatory apparatus in modern humans affects occlusal contact areas between antagonist teeth influencing macrowear and chewing efficiency during ontogeny.

Relationship between tongue pressure and maxillofacial morphology in Japanese children based on skeletal classification

During childhood, perioral muscle function is closely associated with malocclusion. To clarify the effects of tongue function on maxillofacial morphology in children, tongue pressure and maximum lip-closing force (LCF) were measured and the relationship between perioral muscle function and maxillofacial morphology was evaluated according to the skeletal classification. Maximum tongue pressure (MTP) and swallowing tongue pressure (STP) were measured on the anterior palatine rugae in 100 children (Hellman's dental stages IIIA-IIIC) using a balloon-type tongue pressure measurement device. Lip-closing force was measured using an LCF measurement device. Lateral cephalograms were examined to classify subjects into skeletal (S)-I, S-II and S-III groups. Correlations of skeletal classification with tongue pressure and LCF were examined. Correlations of lateral cephalometric measurements with palatal volume (PV), measured using a three-dimensional optical scanner, were evaluated. Maximum tongue pressure was significantly lower in the S-II group than in other groups. Swallowing tongue pressure was significantly lower in the S-II group than in the S-III group. Lip-closing force was significantly higher in the S-III group than in other groups. Swallowing tongue pressure was positively correlated with MTP and PV. Correlations between tongue pressure and anteroposterior skeletal classification indicated the importance of quantitative tongue function assessment.

Analysis of the stomatognathic system of children according orthodontic treatment needs

PURPOSE

The present study evaluated electromyographic activity (EMG), masticatory performance, and tongue strength in children without and with orthodontic treatment needs.

PATIENTS AND METHODS

A total of 90 children were screened and divided into the following groups: Group I (no treatment needed; mean age: 8.00 ± 0.43 years; n = 26), Group II (few malocclusions, treatment needed; mean age: 8.89 ± 0.43 years; n = 28), and Group III (slight-to-borderline treatment needed; mean age: 8.44 ± 0.22 years; n = 36). Orthodontic treatment need was classified on the basis of IOTN-DHC (Index of Orthodontic Treatment Need - Dental Health Component). The electromyographic Trigno EMG Systems was used for muscle analysis and the Iowa Oral Pressure Instrument (IOPI) was used to measure tongue strength. Data were analyzed using normality tests and one-way analysis of variance with a Bonferroni post hoc test (p ≤ 0.05).

RESULTS

EMG in almost all mandibular movements was higher in Group III with statistically significant differences compared to position at rest: right masseter (p = 0.03); protrusion: left temporal (p = 0.02); saliva swallowing: left temporal (p = 0.05) and water swallowing: orbicularis oris mouth, right upper segment (p = 0.05). Lower masticatory performance was found in Group III, but the difference compared to Group I and II was not significant. There were no significant differences between the groups in terms of tongue strength.

CONCLUSIONS

Children with borderline orthodontic treatment needs show functional disorders of the stomatognathic system.

The biomechanical coordination during oropharyngeal swallowing: an evaluation with a non-invasive sensing system

Swallowing is a very important and complex physiological behaviour. The dynamic of swallowing has created great interest as any procedural abnormality will result in dysphagia and even lower quality of life. However, a non-invasive evaluation of biomechanical coordination during oropharyngeal swallowing, which includes the activities of the tongue, the hyoid and swallowing-related muscles, has not yet been achieved. In the present study, we recruited fifteen subjects, and a non-invasive sensing system composed of a pressure sensor, a bend sensor, surface electrodes and a microphone was created to simultaneously monitor tongue pressure, hyoid motion, and surface EMG of swallowing-related muscles, as well as take sound recordings, when the subjects swallowed 5 ml of water. In addition to obtaining the durations of certain motor events, the considerable time (beginning, peak and ending time) of tongue pressure production, suprahyoid and infrahyoid muscle activity and hyoid motion were successfully measured. Moreover, the significant correlations between swallowing-related muscles, tongue pressure, and the hyoid were confirmed. These findings suggest that the non-invasive sensing system has potential as a good candidate for monitoring and evaluating the oropharyngeal process of swallowing, which may be useful in clinical work involving dysphagia evaluation and rehabilitation.

Tongue-Strengthening Exercises in Healthy Older Adults: Specificity of Bulb Position and Detraining Effects

Clinical tongue-strengthening therapy programs are generally based on the principles of exercise and motor learning, including the specificity paradigm. The aim of this study was to investigate the specific effect of anterior and posterior tongue-strengthening exercises (TSE) on tongue strength (TS) in healthy older adults and to measure possible detraining effects. Sixteen healthy elderly completed 8 weeks of TSE by means of the Iowa Oral Performance Instrument (IOPI). They were distributed in two different treatment arms and performed either exclusively anterior or posterior TSE (ATSE, n = 9 or PTSE, n = 7) depending on the treatment arm. Anterior and posterior maximal isometric pressures (MIP_A, MIP_P) were measured at baseline, halfway, and after completion of the training sessions. Detraining was measured by repeating MIP_A and MIP_P measures 4 weeks after the last session of TSE. MIP_A and MIP_P increased significantly in both treatment arms. MIP_A was significantly higher in the ATSE group compared to the PTSE group across all measures in time. No significant differences were observed in MIP_P between the ATSE and PTSE groups. Regardless of treatment arm, there was no significant detraining effect measured 4 weeks after the last TSE session. This study suggests that TSE show partial specificity concerning bulb position. We conclude that especially anterior training results in higher anterior TS in comparison with posterior exercises. Furthermore, we found no detraining effects, independent of bulb location.

Immediate effect of laryngeal surface electrical stimulation on swallowing performance

Surface electrical stimulation of the laryngeal region is used to improve swallowing in dysphagic patients. However, little is known about how electrical stimulation affects tongue movements and related functions. We investigated the effect of electrical stimulation on tongue pressure and hyoid movement, as well as suprahyoid and infrahyoid muscle activity, in 18 healthy young participants. Electrical stimulation (0.2-ms duration, 80 Hz, 80% of each participant's maximal tolerance) of the laryngeal region was applied. Each subject swallowed 5 ml of barium sulfate liquid 36 times at 10-s intervals. During the middle 2 min, electrical stimulation was delivered. Tongue pressure, electromyographic activity of the suprahyoid and infrahyoid muscles, and videofluorographic images were simultaneously recorded. Tongue pressure during stimulation was significantly lower than before or after stimulation and was significantly greater after stimulation than at baseline. Suprahyoid activity after stimulation was larger than at baseline, while infrahyoid muscle activity did not change. During stimulation, the position of the hyoid at rest was descended, the highest hyoid position was significantly inferior, and the vertical movement was greater than before or after stimulation. After stimulation, the positions of the hyoid at rest and at the maximum elevation were more superior than before stimulation. The deviation of the highest positions of the hyoid before and after stimulation corresponded to the differences in tongue pressures at those times. These results suggest that surface electrical stimulation applied to the laryngeal region during swallowing may facilitate subsequent hyoid movement and tongue pressure generation after stimulation. NEW & NOTEWORTHY Surface electrical stimulation applied to the laryngeal region during swallowing may facilitate subsequent hyoid movement and tongue pressure generation after stimulation. Tongue muscles may contribute to overshot recovery more than hyoid muscles.

Real-time MRI of swallowing: intraoral pressure reduction supports larynx elevation

The reduction in intraoral pressure during swallowing has previously been linked to bolus transport, although no such relation has yet been proven. The purpose of this work was to evaluate the time course of intraoral pressure during swallowing using simultaneous real-time magnetic resonance imaging (MRI) and dynamic pressure recordings. Real-time MRI based on highly undersampled radial fast low-angle shot (FLASH) and regularized nonlinear inverse reconstruction was performed at 3 T using a standard head coil and a mid-sagittal section covering the entire oral cavity. Voluntary swallowing (10 mL of pineapple juice or saliva) was monitored for about 30 s in 11 normal subjects at spatial and temporal resolution of 1.3 × 1.3 × 8 mm³ and 40 ms, respectively. Simultaneously, the intraoral atmospheric pressure was recorded at a resolution of 10 ms during the entire course of deglutition. Quantitative measures of bolus transport, larynx elevation and submental muscle changes were obtained from the image series. As a key result, negative intraoral pressure accompanied laryngeal elevation during swallowing in all subjects. A reduction in submental muscle length during swallowing was also observed. No correlations of maximum negative pressure with larynx elevation and submental muscle change were found. In conclusion, intraoral pressure reduction during swallowing is not connected to oral bolus transport, but supports laryngeal elevation by palatal fixation of the tongue.

Study protocol for a randomized controlled trial: tongue strengthening exercises in head and neck cancer patients, does exercise load matter?

BACKGROUND

Reduced tongue strength is an important factor contributing to early and late dysphagia in head and neck cancer patients previously treated with chemoradiotherapy. The evidence is growing that tongue strengthening exercises can improve tongue strength and swallowing function in both healthy and dysphagic subjects. However, little is known about the impact of specific features of an exercise protocol for tongue strength on the actual outcome (strength or swallowing function). Previous research originating in the fields of sports medicine and physical rehabilitation shows that the degree of exercise load is an influential factor for increasing muscle strength in the limb skeletal muscles. Since the tongue is considered a muscular hydrostat, it remains to be proven whether the same concepts will apply.

METHODS/DESIGN

This ongoing randomized controlled trial in chemoradiotherapy-treated patients with head and neck cancer investigates the effect of three tongue strengthening exercise protocols, with different degrees of exercise load, on tongue strength and swallowing. At enrollment, 51 patients whose dysphagia is primarily related to reduced tongue strength are randomly assigned to a training schedule of 60, 80, or 100% of their maximal tongue strength. Patients are treated three times a week for 8 weeks, executing 120 repetitions of the assigned exercise once per training day. Exercise load is progressively adjusted every 2 weeks. Patients are evaluated before, during and after treatment by means of tongue strength measurements, fiber-optic endoscopic evaluation of swallowing and quality-of-life questionnaires.

DISCUSSION

This randomized controlled trial is the first to systematically investigate the effect of different exercise loads in tongue strengthening exercise protocols. The results will allow the development of more efficacious protocols.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN14447678.

Sequential coordination between lingual and pharyngeal pressures produced during dry swallowing

The aim of this study was to investigate oropharyngeal pressure flow dynamics during dry swallowing in ten healthy subjects. Tongue pressure (TP) was measured using a sensor sheet system with five measuring points on the hard palate, and pharyngeal pressure (PP) was measured using a manometric catheter with four measuring points. The order and correlations of sequential events, such as onset, peak, and offset times of pressure production, at each pressure measuring point were analyzed on the synchronized waveforms. Onset of TP was earlier than that of PP. The peak of TP did not show significant differences with the onset of PP, and it was earlier than that of PP. There was no significant difference between the offset of TP and PP. The onset of PP was temporally time-locked to the peak of TP, and there was an especially strong correlation between the onset of PP and TP at the posterior-median part on the hard palate. The offset of PP was temporally time-locked to that of TP. These results could be interpreted as providing an explanation for the generation of oropharyngeal pressure flow to ensure efficient bolus transport and safe swallowing.

Effect of supraglottic and super-supraglottic swallows on tongue pressure production against hard palate

The objectives of this study were to evaluate the state of tongue pressure production during supraglottic swallow (SS) and super-supraglottic swallow (SSS) performed by healthy adults, and to investigate the effects of these swallowing maneuvers on the oral stage of swallowing. The participants were 19 healthy individuals. Tongue pressure against the hard palate during swallowing was measured using a tongue pressure sensor sheet system with five pressure-sensitive points. The tasks comprised swallowing 5 mL of water by normal wet swallow, SS, and SSS, and the parameters for analysis were the duration, the maximal magnitude, and the integrated value of tongue pressure during swallowing. The duration of tongue pressure was significantly longer at the anterior-median part of the hard palate during both SS and SSS than with normal wet swallow. The maximal magnitude increased significantly only at the posterior part of the hard palate during SS, but at all points during SSS. The integrated value increased significantly only at the posterior-median part of the hard palate during SS, but at all points except the mid-median part of the hard palate during SSS. The maximal magnitude and integrated value were also significantly higher at the anterior-median and posterior circumferential parts during SSS than during SS. These results show that these two swallowing maneuvers, which are known primarily as techniques to protect the airway, also function to strengthen the tongue pressure produced by the contact between the tongue and the hard palate during swallowing and this effect is more pronounced during SSS.