Difference in the Electromyographic Behavior of the Masticatory and Swallowing Muscles During Cued Versus Spontaneous Swallowing.

The risk of dysphagia and/or aspiration is determined using screening tests, such as the repeated saliva swallowing test and modified water swallowing test, which evaluate cued swallowing. However, humans masticate and swallow foods with various consistencies, forms, and amounts, without conscious awareness. Therefore, this study aimed to examine the difference in the behavior of masticatory and swallowing muscles during spontaneous versus cued swallowing through a series of mastication and swallowing processes by evaluating surface electromyogram (sEMG) signals. The effect of the consistency and amount of food on the behavior of these muscles was also investigated. The sEMG recordings of the masseter muscles and anterior belly of the digastric muscle for 12 subjects, and genioglossus muscle for 5 subjects were obtained. The genioglossus activity was recorded using custom-made ball electrodes. The test foods were cookies and tofu, in amounts of 2 g and 4 g. The normalized muscle activity (integrated EMG), duration of the muscle activity, initial activation timepoint of each muscle, and total duration of swallowing were compared among four conditions. The activity of each muscle was significantly higher during the swallowing of cookies than tofu, for 4 g vs 2 g, and for cued versus spontaneous swallowing. The duration of each muscle activity, initial activation timepoint, and total duration of swallowing were significantly longer for cookies versus tofu, for 4 g vs 2 g, and for spontaneous versus cued swallowing. These results suggest that the behavior of the masticatory and swallowing muscles is affected by cued swallowing and by the consistency and amount of food.

Sensory neuromuscular electrical stimulation for dysphagia rehabilitation: A literature review.

BACKGROUND: Dysphagia is a common disorder following a cerebrovascular accident. It can cause detrimental effects on patient's quality of life and nutrition intake, especially in older adults. Neuromuscular electrical stimulation has been one of the management strategies for acceleration of the recovery. This review summarises the current evidence on sensory threshold stimulation of the procedure. METHOD: This review compiled data from the Internet database PubMed, Cochrane Library and Scopus using combination of MeSH thesaurus: 'Sensory threshold', 'electrical stimulation', 'neuromuscular stimulation', 'Deglutition', 'Dysphagia'. Eleven studies were intergraded into the review. RESULTS: Most of the studies show significant improvement to the outcomes of sensory neuromuscular electrical stimulation treatment. In many cases, the results of the treatment are comparable or superior to motor threshold stimulation and conventional therapy. However, the study design and parameters of the procedure varied greatly without conclusive standardised guidelines. CONCLUSION: The sensory neuromuscular electrical stimulation (SNMES) is a viable treatment option for treating oropharyngeal dysphagia. The most suggested application parameters are an intensity at sensory threshold, a frequency of 80 Hz, an impulse time of 700 µs, a combined total duration of 20 h of stimulation in a 2-week period, and placing the electrodes in the submental area of the neck. However, further research is necessary to construct a definitive guideline for clinicians.

Medical-Dental Collaboration and Interprofessional Training for Maxillofacial Diseases at Tohoku University Hospital.

The Tohoku University Hospital has been a clinical and research facility for all the related departments of Tohoku University. Medical-dental and interprofessional collaboration has resulted in special treatment teams, made up of members of departments such as the center for head and neck cancer, the center for dysphagia, and the cleft lip and palate center. Those treatment teams held conferences, case study meetings, reading sessions, and in-hospital seminars. The purpose of this study was to evaluate the outcomes of various medical-dental and the interprofessional collaboration at Tohoku University Hospital and training program to equip hospital dentists in higher medical institutions. The attainment targets are the acquisition of basic medical skills and knowledge under the guidance of supervising doctors. As a result, the hospital dentists could acquire their own specialized knowledge and skills certificated by each academic society. The smooth team treatment has been achieved, and the number of cases discussed by cancer boards and center for dysphagia has increased year by year due to the efficiency of their clinical pathways. On the dental care side as well, the wearing rates of maxillofacial prosthetic devices such as maxillofacial prostheses and palatal augmentation prostheses (PAP) have improved, which have contributed to improving patient's stomatognathic function. Tohoku University Hospital has been practicing collaboration between medical and dental professionals and it has produced mutual benefits. Our interprofessional training system based on the medical-dental collaboration could develop professionals who have acquired cross-disciplinary knowledge and skills from experienced doctors.

Relationships Between Survival and Oral Status, Swallowing Function, and Oral Intake Level in Older Patients with Aspiration Pneumonia.

The factors affecting the survival of patients with aspiration pneumonia (AP) remain unclear. This study aimed to determine whether factors, including oral status, swallowing function, and oral intake level, were related to survival outcomes in older patients hospitalized for AP. The study enrolled patients with AP who were admitted to our hospital between February 2017 and November 2019. Patients were divided into two groups based on the 90-day mortality after the first swallowing function evaluation: survivors and deceased. The data were compared between the two groups. A total of 29 patients were diagnosed with AP. Of these patients, 13 died within 90 days. The numbers of patients who could not use removable dentures and required sputum suctioning and had cough reflex at rest were significantly higher in the deceased than in the survivors. The salivary pooling and pharyngeal clearance scores evaluated by videoendoscopy, International Dysphagia Diet Standardisation Initiative Functional Diet Scale score determined after swallowing function evaluation, and consciousness level were significantly worse in the deceased than in the survivors. There were significant differences in patients' oral status, swallowing function, oral intake level, and consciousness level between the survivors and deceased.

Effect of surface modification of Ti-6Al-4V alloy by electron cyclotron resonance plasma oxidation.

Ti-6Al-4V alloy is used as biomaterials for dental and orthopedic implants because of their excellent biocompatibilities and mechanical properties. However, it is unclear that electron cyclotron resonance (ECR) plasma oxidation can create the oxide films on Ti-6Al-4V alloy surface, and this technique improves the ability of its osseointegration. The purpose of this study was to investigate the characteristics and calcification ability of the oxide films. X-ray diffraction (XRD) peaks of rutile phase were intensified with increasing the temperature. Scanning electron microscopy (SEM) images showed a crater-like structure, and bonding strengths between the substrate and oxide film reached a maximum at 400°C. Calcium phosphate (CaP) compounds after calcification process were identified as octacalcium phosphate (OCP) and precipitation amount was maximized at 400°C. The results suggested that the altered surface of Ti-6Al-4V alloy by ECR plasma oxidation might have the potential of accelerating the ability of its osseointegration through enhancement of OCP.

Sustained laryngeal transient receptor potential vanilloid 1 activation inhibits mechanically induced swallowing in anesthetized rats.

A major component of gastric acid is hydrochloric acid (HCl), which can activate transient receptor potential vanilloid 1 (TRPV1). In the present study, we investigated how sustained laryngeal TRPV1 activation affects the frequency of the swallowing reflex. Experiments were carried out on 85 male Sprague-Dawley rats. The effects of short and sustained application of chemicals (3 µl of 0.1 N HCl or capsaicin) on the frequency of swallowing and on time-dependent changes in the occurrence of swallowing evoked by supralaryngeal nerve stimulation were determined. To evaluate vascular permeability of the larynx, Evans blue dye was intravenously injected after 5 or 60 min of sustained TRPV1 activation. SB366791 (a TRPV1 inhibitor) and Cap/QX-314 (a TRPV1-expressed neuronal inhibitor) significantly inhibited HCl/capsaicin-induced swallowing, but air flow-induced swallowing was not affected. Although the number of air flow-induced swallows followed by capsaicin stimulation was not affected within 5 min, it was significantly reduced by 60-min capsaicin or HCl application. The swallowing threshold associated with supralaryngeal nerve stimulation did not significantly change throughout the recording period. Evans blue dye concentrations in the larynx were significantly higher at 60 min in the 10-5 M capsaicin group than in the control group. Our results suggest that sustained TPRV1 activation not only desensitizes TRPV1 but also inactivates mechanoreceptors, which may be attributed to increases in vascular permeability and edema, as part of an inflammatory process.NEW & NOTEWORTHY Although a transient receptor potential vanilloid 1 (TRPV1) inhibitor or TRPV1-expressed neuronal inhibitor significantly inhibited HCl/capsaicin-evoked swallowing, air flow-induced swallowing was not affected. The number of air flow-induced swallows was significantly reduced within 60 min of TRPV1 activation. Evans blue dye concentration in the larynx increased 60 min after capsaicin application. TPRV1 activation not only desensitizes TRPV1 but also inactivates mechanoreceptors caused by increases in vascular permeability and edema.

Design and Progress of Oral Health Examinations in the Tohoku Medical Megabank Project.

In order to assess the long-term impact of the Great East Japan Earthquake on the oral health of disaster victims and to evaluate gene-environmental interactions in the development of major oral diseases and oral-systemic associations, the oral part of two large-scale genome cohort studies by the Tohoku Medical Megabank Organization (ToMMo), including the Community-based cohort (CommCohort) study and the Birth and Three-Generation cohort (BirThree) study, have been conducted. The study population comprised 32,185 subjects, including 16,886 participants in the CommCohort study and 15,299 participants in the BirThree cohort study, recruited from 2013 to 2017. The oral studies consist of a questionnaire regarding oral hygiene behavior, clinical examinations by dentists, and oral plaque and saliva sampling for microbiome analyses, which were carried out at seven community support centers in Miyagi prefecture. The median age of all participants was 55.0 years, and 66.1% of participants were women. Almost all participants reported that they brushed their teeth more than once a day. The median number of present teeth was 27.0, and the decayed, missing and filled tooth number was 16.0, with a significant difference according to age and sex. The median periodontal pocket and clinical attachment level was 2.48 mm and 4.00 mm, respectively. Periodontal parameters increased significantly according to age, except for the accumulation of dental calculus. The oral part of these extensive cross-sectional studies provides a unique and important platform for future studies on oral health and diseases that elicit through interactions with systemic diseases, lifestyles, life events and genetic backgrounds, and contributes to researches clarifying the long-term effects of disasters on oral health.

Histomorphometric assessments of peri-implant bone around Ti-Nb-Sn alloy implants with low Young's modulus.

Many ß-Ti alloys have been developed for, and used in, medical devices because of the corrosion resistance, biocompatibility, and exceptionally low Young's modulus. The aim of the present study was to investigate the histomorphometric aspects of peri-implant bone around Ti-Nb-Sn alloy implants and compare them with those in the case of commercially pure Ti (Ti). Fluorescent morphological observations of ST-2 cells on the substrate were performed and bone morphogenesis around implants in rat femur was evaluated. There was no difference between the cell morphology on Ti and those on the Ti-Nb-Sn alloy during observation for 24 h. A comparison of the Ti-Nb-Sn alloy implant and the Ti implant showed no significant differences between the bone-to-implant contact ratios or the bone fractions. These results suggest that the biological adaptations with Ti-Nb-Sn implants during a healing period are similar to those with Ti. Ti-Nb-Sn is therefore suitable for use in dental implants.

Involvement of the epithelial sodium channel in initiation of mechanically evoked swallows in anaesthetized rats.

KEY POINTS: Afferents carried by the superior laryngeal nerve play a primary role in the initiation of laryngeal mechanically evoked swallows in anaesthetized rats. Amiloride and its analogues inhibit swallowing evoked by mechanical stimulation, but not swallowing evoked by chemical and electrical stimulation. The epithelial sodium channel is probably involved in the initiation of laryngeal mechanically evoked swallows. ABSTRACT: The swallowing reflex plays a critical role in airway protection. Because impaired laryngeal mechanosensation is associated with food bolus aspiration, it is important to know how the laryngeal sensory system regulates swallowing initiation. This study was performed to clarify the neuronal mechanism of mechanically evoked swallows. Urethane-anaesthetized Sprague-Dawley male rats were used. A swallow was identified by activation of the suprahyoid and thyrohyoid muscles on electromyography. The swallowing threshold was measured by von Frey filament and electrical stimulation of the larynx. The number of swallows induced by upper airway distension and capsaicin application (0.03 nmol, 3 µl) to the vocal folds was counted. The effects of topical application (0.3-30 nmol, 3 µl) of the epithelial sodium channel (ENaC) blocker amiloride and its analogues (benzamil and dimethylamiloride), acid-sensing ion channel (ASIC) inhibitors (mambalgine-1 and diminazene) and gadolinium to the laryngeal mucosa on swallowing initiation were evaluated. A nerve transection study indicated that afferents carried by the superior laryngeal nerve play a primary role in the initiation of laryngeal mechanically evoked swallows. The mechanical threshold of swallowing was increased in a dose-dependent manner by amiloride and its analogues and gadolinium, but not by ASIC inhibitors. The number of swallows by upper airway distension was significantly decreased by benzamil application. However, the initiation of swallows evoked by capsaicin and electrical stimulation was not affected by benzamil application. We speculate that the ENaC is involved in the initiation of laryngeal mechanically evoked swallows.

Introduction of integrated dental training jaw models and rubric criteria.

OBJECTIVE: The objective of the present study was to evaluate the effectiveness of introducing integrated jaw models, rubric criteria and homework tasks to a total clinical simulation training course to improve the clinical competence of preclinical dental students. METHODS: A total simulation training course, which involved six clinical dentistry departments, was held for 110 preclinical students in 2014 and 2015. We prepared integrated jaw models having several morbidities along with corresponding medical information and homework tasks. The students formulated diagnoses and devised treatment plans before performing dental treatment on the mannequin under the direction of instructors from the respective clinical departments. Their performance was assessed by both students and instructors using the rubric criteria. RESULTS: Based on quantitative evaluations, the introduction of integrated jaw models appeared to improve the students' ability to formulate diagnoses and devise dental treatment plans and to understand the respective clinical dentistry disciplines. The rubric criteria provided immediate feedback for the students. Based on a comparison of rubric scores, students tended to significantly underestimate their own performance compared with instructors. Moreover, the introduction of homework tasks improved student seriousness. CONCLUSION: Introducing integrated jaw models, rubric criteria and homework tasks to a total simulation training course may be a good approach for improving student performance in terms of dental diagnoses and treatment.

Involvement of hypoglossal and recurrent laryngeal nerves on swallowing pressure.

Swallowing pressure generation is important to ensure safe transport of an ingested bolus without aspiration or leaving residue in the pharynx. To clarify the mechanism, we measured swallowing pressure at the oropharynx (OP), upper esophageal sphincter (UES), and cervical esophagus (CE) using a specially designed manometric catheter in anesthetized rats. A swallow, evoked by punctate mechanical stimulation to the larynx, was identified by recording activation of the suprahyoid and thyrohyoid muscles using electromyography (EMG). Areas under the curve of the swallowing pressure at the OP, UES, and CE from two trials indicated high intrasubject reproducibility. Effects of transecting the hypoglossal nerve (12N) and recurrent laryngeal nerve (RLN) on swallowing were investigated. Following bilateral hypoglossal nerve transection (Bi-12Nx), OP pressure was significantly decreased, and time intervals between peaks of thyrohyoid EMG bursts and OP pressure were significantly shorter. Decreased OP pressure and shortened times between peaks of thyrohyoid EMG bursts and OP pressure following Bi-12Nx were significantly increased and longer, respectively, after covering the hard and soft palates with acrylic material. UES pressure was significantly decreased after bilateral RLN transection compared with that before transection. These results suggest that the 12N and RLN play crucial roles in OP and UES pressure during swallowing, respectively. We speculate that covering the palates with a palatal augmentation prosthesis may reverse the reduced swallowing pressure in patients with 12N or tongue damage by the changes of the sensory information and of the contact between the tongue and a palates. NEW & NOTEWORTHY Hypoglossal nerve transection reduced swallowing pressure at the oropharynx. Covering the hard and soft palates with acrylic material may reverse the reduced swallowing function caused by hypoglossal nerve damage. Recurrent laryngeal nerve transection reduced upper esophageal sphincter negative pressure during swallowing.

Development of semi-automatic procedure for detection and tracking of fiducial markers for orofacial kinematics during natural feeding.

Feeding is a highly complex, essential behavior for survival in all species. Characterization of feeding behaviors has implications in basic science and translational medicine. We have been developing methods to study feeding behaviors using high speed videofluoroscopy (XROMM) in rats while self-feeding radiopaque flavored kibble. The rat is a popular model in translational medicine; however, it has not been studied using this methodology. Towards this goal, we surgically implanted radiopaque fiducial markers into the skull, mandible, and tongue of rats to enable motion tracking. We are developing computer vision tools to extract kinematics and behavioral features from XROMM videos to overcome barriers of current analysis methods. By understanding feeding dynamics, we will gain basic scientific knowledge and translational insights for feeding disorders caused by neurological conditions such as ALS, Parkinson's disease, and stroke.

Biomechanical evaluation of Ti-Nb-Sn alloy implants with a low Young's modulus.

Dental implants are widely used and are a predictable treatment in various edentulous cases. Occlusal overload may be causally related to implant bone loss and a loss of integration. Stress concentrations may be diminished using a mechanobiologically integrated implant with bone tissue. The purpose of this study was to investigate the biomechanical behavior, biocompatibility and bioactivity of a Ti-Nb-Sn alloy as a dental implant material. It was compared with cpTi. Cell proliferation and alkaline phosphatase (ALP) activity were quantified. To assess the degree of osseointegration, a push-in test was carried out. Cell proliferation and ALP activity in the cells grown on prepared surfaces were similar for the Ti-Nb-Sn alloy and for cpTi in all the experiments. A comparison between the Ti-Nb-Sn alloy implant and the cpTi implant revealed that no significant difference was apparent for the push-in test values. These results suggest that implants fabricated using Ti-Nb-Sn have a similar biological potential as cpTi and are capable of excellent osseointegration.

Proteome analysis of rat serum proteins adsorbed onto synthetic octacalcium phosphate crystals.

The present study was designed to determine which proteins are selectively adsorbed onto two bone substitute materials, octacalcium phosphate (OCP) and hydroxyapatite (HA) crystals, from rat serum by proteome analysis. Ground crystals of synthetic OCP and commercially available sintered HA, with the same surface area, were incubated in rat serum proteins at 37°C for 24 h. The proteins from the crystals extracted with guanidine-HCl-EDTA were listed on the basis of the results of liquid chromatography tandem mass spectrometry (LC/MS/MS). A total of 138 proteins were detected from OCP; 103 proteins were detected from HA. Forty-eight proteins were from both crystals. A quantitative analysis of the proteins detected was performed for the extracted two bone formation-related proteins apolipoprotein E (Apo E), a protein known to promote osteoblast differentiation, and complement 3 (C3). HA adsorbed C3 (3.98 ± 0.03 fmol/µg protein) more than OCP (1.81 ± 0.07 fmol/µg protein) did, while OCP adsorbed Apo E (2.42 ± 0.03 fmol/µg protein) more than HA (1.21 ± 0.01 fmol/µg protein) did even after deleting the high-abundance proteins, such as albumin. The results demonstrated that OCP exhibits a similar property but distinct capacity with HA in adsorbing bone formation-related proteins from the serum constituents.

Preparation and characterization of porous alginate scaffolds containing various amounts of octacalcium phosphate (OCP) crystals.

The present study was designed to investigate whether the amount of octacalcium phosphate (OCP) affects the characteristics of alginate (Alg)/OCP scaffolds regarding the pore formation and its distribution, and the thermodynamic stability from OCP to hydroxyapatite (HA) in an in vitro physiological environment. Alg/OCP composites with weight ratios of 100/0, 75/25, 50/50, and 25/75 were prepared through mixing the ground synthesized OCP crystals with an Alg solution and applying lyophilization. Analysis of X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and mercury intrusion porosimetry verified that the crystalline phase of OCP and the porosities were retained regardless of the OCP amount. On the other hand, the elastic modulus, determined by mechanical testing, and, interestingly, the pore size increased with increasing the OCP amount. The immersion of the composites in a simulated body fluid up to 14 days revealed that OCP in Alg matrices tends to convert to HA with enhancing the calcium consumption depending on the OCP amount. The results indicated that the inclusion of OCP crystals in the Alg matrix by the mixing process controls the character of the pore distribution in Alg/OCP composites while maintaining the transitory nature of OCP.