Effect of oral intake initiation-establishment interval on hospital stay after oral cancer surgery.

OBJECTIVES: To clarify the effect of the period between initiation of oral intake (IOI) and establishment of oral intake (EOI) on length of hospital stay. METHODS: This retrospective study included postoperative oral cancer patients. The number of days from surgery to IOI and EOI and between IOI and EOI were recorded. We performed intergroup comparisons and Cox regression analysis using the number of days until discharge, representing hospital stay length as the dependent variable. RESULTS: The median number of days between IOI and EOI was 3 days for eligible patients and 4.5 and 1.5 for older and younger patients, respectively. The median number of days from surgery to IOI was 15 days. There was a significant correlation between the period between IOI and EOI and the length of hospital stay (r = 0.40, p < 0.01). The period between IOI and EOI was a significant independent variable for the length of hospital stay (HR [95% confidence interval] = 0.45 [0.28-0.72]). CONCLUSIONS: Shortening the IOI to EOI intervals was identified as an independently associated factor for shortening hospital stay, even in older postoperative patients with dysphagia who struggled with early oral intake initiation. Professional, step-by-step dysphagia rehabilitation tailored to the patient's condition yields beneficial outcomes.

Application of transition-edge sensors for micro-X-ray fluorescence measurements and micro-X-ray absorption near edge structure spectroscopy: a case study of uranium speciation in biotite obtained from a uranium mine.

In this study, we successfully applied a transition-edge sensor (TES) spectrometer as a detector for microbeam X-ray measurements from a synchrotron X-ray light source in the hard X-ray region to determine uranium (U) distribution at the micro-scale and its chemical species in biotite obtained from a U mine. It is difficult to separate the fluorescent X-ray of the U Lα1 line at 13.615 keV from that of the Rb Kα line at 13.395 keV in the X-ray fluorescence spectrum with an energy resolution of approximately 220 eV using a conventional silicon drift detector (SDD). Meanwhile, the fluorescent X-rays of U Lα1 and Rb Kα were fully separated by a TES with 50 eV energy resolution at an energy of around 13 keV. The successful peak separation by the TES led to an accurate mapping analysis of trace U in micro-X-ray fluorescence measurements and a decrease in the signal-to-background ratio in micro-X-ray absorption near edge structure spectroscopy. Thus, it could be a powerful tool for studying the U distribution and speciation in various environmental samples.

Usefulness of a newly developed endoscope for the observation of the posterior tracheal wall.

Objective: Videoendoscopic evaluation of swallowing is an objective swallowing function evaluation method used in dysphagia rehabilitation. However, it is anatomically difficult to detect the entry of foreign substances through the posterior tracheal wall using a conventional endoscope (CE). In this study, we developed an endoscope that can observe the posterior tracheal wall and investigated its reliability and validity in healthy adults. Methods: Twenty healthy adults were included. The trachea was observed from inside the larynx using a CE and a portable, flexible two-step angulation endoscope (two-AE) with a two-step curved shaft tip. The visibility of the anterior and posterior walls was recorded. The time from the endoscope tip entering the larynx to the posterior tracheal wall was measured. Additionally, discomfort events were assessed after the examination. McNemar's test and a paired t-test were used for statistical analysis. Kappa coefficients and concordance rates were calculated. Results: The anterior tracheal wall was observed using both endoscopes. The posterior tracheal wall was significantly observed in 18 participants with the two-AE (p < .001), compared to only three of 20 participants with the CE. The time to observation of the posterior tracheal wall for examiners 1 and 2 was 13.3 ± 6.5 and 12.0 ± 6.7 s, respectively, with no difference between groups (p = .400). The kappa coefficients of examiners 1 and 2 and between the examiners were 0.444, 0.643, and 0.643, respectively, with concordance rates of 90%, 95%, and 95%, respectively. Conclusion: Regardless of the examiner's years of experience, we observed that the two-AE could observe the posterior tracheal wall. Level of Evidence: Step 5.

Effects of tongue right positioner use on tongue pressure: a pilot study.

The effectiveness of the tongue right positioner (TRP) use on oral and swallowing functions remains unclear. To investigate the effects of TRP use on tongue function in patients with dysphagia. This interventional study included eight participants with dysphagia who visited a university dental hospital. The measurement variables included tongue pressure (TP) as the primary outcome and lip and tongue movements, peak nasal inspiratory flow, and changes in the tongue and suprahyoid muscle regions on ultrasonography as the secondary outcomes. Each participant was asked to use a TRP for at least 8 h every night for 2 months. The measurement variables before and after the intervention were compared using the paired t test and Wilcoxon signed-rank test. TP after intervention (31.5 ± 13.1 kPa) was significantly higher than that before intervention (23.0 ± 13.4 kPa), while other measurement variables did not significantly improve. Numerous exercises have been suggested to improve TP; however, most require patients' adherence to instructions. In contrast, although participants did not perform active exercises, most participants in this study observed an improved TP. Our findings show that TRP can greatly improve TP after 2 months of usage.Trial registration number: University Hospital Medical Information Network Clinical Trials Registry (UMIN000040253, date of first registration: 27/04/2020).

High-sensitive XANES analysis at Ce L2-edge for Ce in bauxites using transition-edge sensors: Implications for Ti-rich geological samples.

Accurate determination of cerium (Ce) valence state is important for interpreting the Ce anomaly in geological archives for (paleo)redox reconstruction. However, the routine application of Ce L3-edge X-ray absorption near-edge structure (XANES) spectroscopy for detecting trace Ce in geological samples can often be restricted by coexisting titanium (Ti) due to the proximity of their fluorescence emission lines. Therefore, the signal-to-noise ratio of Ce L3-edge XANES spectra may not be sufficiently high for high-quality spectroscopic analysis. This study introduces a semi-quantitative approach appropriate for Ti-rich, Ce-dilute geological materials by synchrotron-based X-ray measurement at the Ce L2-edge. First, the results confirm that Ce L2-edge XANES spectra are able to avoid overlapping Ti Kß emissions and provide more reliable information on the Ce valence state in Ti-rich materials relative to L3-edge XANES. Moreover, the application of transition-edge sensor (TES) could reach the higher sensitivity with better energy resolution than conventional silicon drift detector (SDD) to detect fluorescence X-ray (Ce Lß1). The investigation on bauxites developed from the Columbia River Basalts shows that combining Ce L2-edge XANES and TES allows for resolving weak Ce fluorescence lines at the L2-edge from Ti-rich, Ce-dilute samples (Ti/Ce mass ratio up to ∼6000, tens of ppm Ce). The outcome emphasizes the practical possibility of investigating Ce redox state in Ti-rich geological samples.

Higher extracellular water/total body water ratio is associated with lower tongue and grip strength: A cross-sectional study.

PURPOSE: This study aimed to investigate the relationship between tongue factors (tongue strength and tongue volume), systemic factors (grip strength and walking speed), and the extracellular water/total body water ratio. METHODS: This cross-sectional study included community-dwelling adults. Body water composition and skeletal muscle mass index were measured using bioelectrical impedance analysis. Moreover, tongue grip strength, tongue volume, occlusal support condition (Eichner classification), and walking speed were measured. Multiple linear regression analysis was performed to investigate the relationship between the tongue and systemic factors as dependent variables and body water composition. RESULTS: We included 171 community-dwelling adults (62 men and 109 women) aged 70.0 years (interquartile range: 8). Tongue strength (r=-0.22, P=0.004) and grip strength (r=-0.39, P<0.001) were correlated with the extracellular water/total body water ratio. In multiple linear regression analysis, tongue strength was associated with the extracellular water/total body water ratio (ß=-0.20, P=0.034), and grip strength was associated with the extracellular water/total body water ratio (ß=-0.12, P=0.047), sex, body mass index, skeletal muscle mass index, and occlusal support condition. CONCLUSIONS: A higher extracellular water/total body water ratio indicates lower tongue and grip strength. Dentists and dental hygienists should be aware of systemic factors present in patients with lower tongue and grip strength. These findings may lead to further medical investigations and diagnosis of other systemic diseases.

Time Spent Away from Bed to Maintain Swallowing Function in Older Adults.

INTRODUCTION: The aim of this study was to determine the associations of time spent away from bed with whole-body muscle mass and swallowing function in older adults with low activities of daily living (ADL). METHODS: This cross-sectional study was conducted at Tokyo Medical and Dental University and included adults over 65 years of age who underwent a medical intervention at their residence. Data regarding age, sex, body height and weight, activity status, medical history, time spent away from bed, and Functional Oral Intake Scale (FOIS) were collected. We calculated the body mass index, Charlson Comorbidity Index, whole-body muscle mass, the appendicular skeletal muscle mass index (ASMI), and the trunk muscle mass index (TMI). According to the time spent away from bed, the subjects were grouped as follows: <4 but ≥0 h (S), <6 but ≥4 h (M), and ≥6 h (L). These variables were analyzed using the one-way analysis of variance, the Kruskal-Wallis test, and the χ2 test, then differences among the three groups were examined. To adjust for confounding factors, we performed multiple regression analysis with ASMI and TMI as the dependent variables and ordinal logistic regression analysis with FOIS as the objective variable. RESULTS: Ninety subjects (male: n = 42; female: n = 48; mean age = 82.9 ± 8.8 years, and groups S: n = 23; M: n = 30; L: n = 37) were analyzed. Group L had a significantly higher ASMI, TMI, and FOIS score than groups S and M, while group M had a significantly higher ASMI and FOIS score than group S. After adjusting for confounding factors, the significant explanatory factors for ASMI were sex, activity status, time spent away from bed, and TMI. The factors for TMI were activity status, time spent away from bed, ASMI, and FOIS. The factors for FOIS were time spent away from bed and TMI. CONCLUSION: Spending 4 or more hours away from the bed is related to appendicular skeletal muscle mass and FOIS, while spending 6 or more hours is related to appendicular skeletal muscle mass, trunk muscle mass, and FOIS in this population. These findings highlight factors that can prevent a decline in swallowing function in the daily life of older adults with low ADL who have difficulty performing exercises to preserve swallowing function.

Strength and morphology of a suprahyoid muscle and their relationship to forward head posture in healthy older adults.

AIM: Forward head posture, an abnormality in head and trunk positioning, adversely affects suprahyoid muscle activity. Jaw-opening force, which reflects suprahyoid muscle strength, is a useful index of dysphagia. However, the relationship between forward head posture and strength and morphology of suprahyoid muscles remains unclear. This study aims to clarify the relationship between forward head posture, jaw-opening force and morphology of suprahyoid muscles. METHODS: During October 2018, we enrolled older adults aged ≥65 years. The craniovertebral angle was measured, and an angle <49° was defined as forward head posture. Jaw-opening force was also measured. The geniohyoid muscle (GHM) was selected to represent the suprahyoid muscles, and its cross-sectional area and length were measured using ultrasonography. Sarcopenia was also determined based on the criteria of the 2019 Asian Working Group for Sarcopenia. Multiple regression analyses were conducted to determine the association between morphological characteristics of the suprahyoid muscle and jaw-opening force as well as the association between the former and forward head posture. RESULTS: Data of 87 participants were analyzed. Sex, cross-sectional area and length of the GHM, and sarcopenia were significantly associated with jaw-opening force. In addition, sex and forward head posture were significantly associated with the length of the GHM. CONCLUSIONS: Our study demonstrated that an overextended length of suprahyoid muscles mediates the relationship between forward head posture and jaw-opening force. Forward head posture is easily visualized and can be a useful indicator of decline in suprahyoid muscle strength. Geriatr Gerontol Int 2022; 22: 779-784.

Bio-signal Feature Analysis to Detect Aspiration Caused by Dysphagia.

Dysphagia causes aspiration symptoms and can trigger aspiration pneumonia, poor nutritional status, etc. To address these risks, it is important to properly evaluate dysphagia and link it with treatment and training. However, current dysphagia evaluation methods cannot assess a swallowing function equivalent to that in daily life, owing to the examination method and environment. In this study, we analyzed bio-signal features to realize a system that can detect aspiration symptoms in daily life. Focusing on the neck electrical impedance, swallowing sounds, and a surface electromyogram of the suprahyoid muscles, we created a swallowing-measurement device and analyzed the bio-signals of the throat movement during swallowing. By measuring the swallowing of dysphagic patients, we investigated the characteristic differences, depending on the presence or absence of aspiration symptoms. The analysis results suggest that there were differences in each bio-signal depending on the presence or absence of aspiration symptoms, and these bio-signals could detect aspiration symptoms. This method can detect aspiration symptoms in daily life and evaluate dysphagia more appropriately and simply than current evaluation methods.

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 (ß = 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.

The Cross-Sectional Area of the Middle and Base of the Tongue is Associated with Swallowing-Related Muscle Strength.

Muscle strength and function are generally positively correlated with muscle quantity and negatively correlated with muscle quality; however, the tongue shows a unique tendency, different from limb muscles. The relationship between the characteristics of each part of the tongue, muscle strength and function, and systemic factors has been unclear. The aim of the study was to investigate the relationship between cross-sectional area (CSA) and echo intensity (EI) of the middle and base of the tongue and swallowing, articulation function, and body composition. Eighty-nine healthy individuals were included in this cross-sectional study. Swallowing was assessed using tongue pressure (TP) and jaw opening force (JOF) as they indicate swallowing-related muscle strength. Articulation function was evaluated through oral diadochokinesis (ODK). Bioelectrical impedance analysis was performed for body composition. CSAs and EIs of the middle and base of the tongue were measured using ultrasound. Multiple regression analysis was used to examine the relationship between the characteristics of the tongue, swallowing-related muscle strength, and ODK. In multiple regression analysis with TP as the dependent variable, age (ß = - 0.22, P < 0.01) and CSA of the middle part (ß = 0.02, P < 0.01) were significant explanatory variables. In multiple regression analysis with JOF as the dependent variable, sex (ß = - 2.76, P < 0.01) and CSA of the base (ß = - 0.004, P < 0.05) were significant explanatory variables. Multiple regression analysis with articulation function as the dependent variable did not yield significant results. The CSA of the tongue is a better indicator of swallowing-related muscle strength than EI. Ultrasonography may be used for assessing swallowing-related muscle strength.

Jaw-Opening Force as a Useful Index for Dysphagia: A Cross-Sectional and Multi-Institutional Study.

INTRODUCTION: Jaw-opening force (JOF) can be a potential screening tool for dysphagia. However, confounding variables such as comorbidities or physical and oral functions that are associated with the physiology of swallowing have not previously been examined. Adjusting for these variables could reveal the relationship between JOF and dysphagia and indicate whether JOF is an independent factor associated with dysphagia. We therefore aimed to assess the efficacy of using JOF for dysphagia screening in this multi-institutional study. METHODS: Community-dwelling older adults over the age of 65 years (N = 403) who visited the university dental hospitals and participated in health surveys (mean age ± standard deviation, 77.1 ± 7.0 years; range, 65-96 years) between November 2018 and January 2020 were included in this study. The JOFs of all participants were measured. The measured JOF was compared with the presence of dysphagia, which was defined using the Functional Oral Intake Scale and the Eating Assessment Tool-10. RESULTS: Multiple logistic regression analysis revealed that the presence of dysphagia was independently associated with JOF, calf circumference, and dependence after adjusting for age and sex. DISCUSSION/CONCLUSION: Decreased JOF can be a risk factor for dysphagia in older adults.

Jaw-retraction exercise increases anterior hyoid excursion during swallowing in older adults with mild dysphagia.

OBJECTIVES: The present study aimed to evaluate the effectiveness of a newly designed jaw-retraction exercise for strengthening the geniohyoid muscle and thus improving the anterior movement of the hyoid bone during swallowing. BACKGROUND: Although previous studies suggest a relationship between anterior hyoid excursion and upper esophageal sphincter (UES) opening, there are currently no reports of physical exercises without the use of special equipment that can effectively improve this movement of the hyoid bone during swallowing. MATERIALS AND METHODS: This before-after study included patients presenting to the authors' hospital with mild dysphagia (Level 5 on the Dysphagia Outcome and Severity Scale). The participants were instructed to perform a jaw-retraction exercise designed to strengthen the geniohyoid muscle. Each participant was instructed to perform two sets of the exercise daily for four weeks, with each set consisting of five repetitions. Before and after the four-week training period, videofluoroscopic swallowing studies were performed and later analysed. RESULTS: Twenty-five patients with a median age of 77 were included. The median peak anterior hyoid position before and after exercise were 129.82 and 132.74 (%C2-C4 length), respectively, and this increase was found to be significant (P = .007). The median extent of UES opening before and after exercise were 8.6 and 9.3 (mm), respectively, and this increase was also found to be significant (P = .040). CONCLUSION: Our findings demonstrate that the jaw-retraction exercise can effectively improve the anterior movement of the hyoid bone. This exercise may be effective in individuals with oral frailty when signs of swallowing disorders are observed.

Higher Activity and Quality of Life Correlates with Swallowing Function in Older Adults with Low Activities of Daily Living.

INTRODUCTION: The aim of this study was to clarify the relationship among swallowing function, activity, and quality of life (QOL) in older adults with low activities of daily living (ADL). MATERIALS AND METHODS: We conducted a cross-sectional study. In total, 271 Japanese adults aged over 65 years who underwent medical intervention at their residence (male: n = 107; female: n = 164; mean age = 84.6 ± 8.3 years) participated. We collected data regarding age, sex, body mass index (BMI), residence (their house/nursing home), activity status, consciousness level (eye response), history of aspiration pneumonia, other medical history, number of medication types, frequency of going out, and time spent away from bed. We judged consciousness level (eye response) using the Glasgow Coma Scale (GCS), calculated the Charlson comorbidity index, measured QOL using the short version of the Quality of Life Questionnaire for Dementia (short QOL-D), and assessed swallowing function using the Functional Oral Intake Scale (FOIS). To examine the relationship between scores for the FOIS and the other variables, we used the Spearman rank correlation coefficient and ordinal logistic regression analysis. RESULTS: The FOIS was strongly correlated with BMI (ρ = 0.47), activity status (ρ = -0.60), GCS (ρ = -0.41), time spent away from bed (ρ = 0.56), scores for the short QOL-D (ρ = 0.40), weakly correlated with history of aspiration pneumonia (ρ = -0.27), and frequency of going out (ρ = 0.39). Results for the ordinal logistic regression analysis showed that the FOIS was associated with activity status, frequency of going out, time spent away from bed, and scores for the short QOL-D. CONCLUSION: The swallowing function of older adults with low ADL was related to their QOL and activities, such as time spent away from bed and home. Thus, in rehabilitation programs for swallowing function in older adults, not only functional but also psychological approaches may prove effective.

Can Videofluoroscopic Swallowing Kinematic Analysis Predict Recovery of Oral Intake in Postoperative Oral Cancer Patients Requiring Nasogastric Tube Feeding?

This retrospective study determined the significant predictive factors for the number of days required to remove nasogastric tubes (NGTs) after surgery in patients with oral cancer (OC). In this study, patients underwent a videofluoroscopic swallowing study (VFSS) approximately 2 weeks after surgery. Videofluoroscopic images were analyzed, and variables such as swallowing and swallowing kinematics were measured. Patient characteristics, swallowing kinematics, and swallowing results were assessed using a Cox proportional hazards model. This study assessed 129 participants (66 men, 63 women, mean age: 69.0 ± 14.1 years) with nine types of cancer. The Cox proportional hazard ratio revealed that sex, body mass index before surgery, radiotherapy and/or chemotherapy, dysphagia before surgery, normalized pharyngeal constriction ratio, upper esophageal sphincter (UES) opening, and laryngeal vestibule disclosure (LVC) disorder were predictive factors for the removal of NGTs when adjusted for age. The study identified several predictive factors for the removal of NGTs and oral intake recovery in patients with OC. Regarding swallowing kinematics, UES opening is the most significant predictive factor. After surgery for OC, VFSS should be performed to assess safe eating methods and predict the recovery of oral intake and removal of the NGT.

Effect of isometric exercises on the masseter muscle in older adults with missing dentition: a randomized controlled trial.

Maintaining oral function in older individuals with missing teeth is important for leading a healthy and independent life. This study aimed to evaluate whether simple isometric exercises can maintain and improve the oral function [maximum occlusal force (MOF) and masticatory ability (MA)] and the masticatory muscle properties [masseter muscle thickness (MMT) and echo intensity (MMEI)] in older adults during the maintenance phase of removable prosthetic treatment. Participants were randomly categorized into the intervention and control groups. The mouthpieces were distributed, and participants were instructed to use them for exercising. The intervention group was instructed to perform maximum clenching for 10 s, whereas the control group was instructed to tap the teeth at an arbitrary speed for 10 s. Both were repeated five times at an interval of 5 s between each activity and twice daily for 4 weeks. The outcomes were measured after a month of exercise. The intervention group showed a significant improvement in the MOF, MMT during contraction, MMT at rest and MMEI during contraction. There were no significant differences in the MA and MMEI at rest. In the control group, no improvement was observed in any of the parameters. When the isometric exercises were performed using a mouthpiece, there was an improvement in the oral function and masseter muscle properties in older individuals with Eichner B status who used dentures.

Broadband high-energy resolution hard x-ray spectroscopy using transition edge sensors at SPring-8.

We have succeeded in operating a transition-edge sensor (TES) spectrometer and evaluating its performance at the SPring-8 synchrotron x-ray light source. The TES spectrometer consists of a 240 pixel National Institute of Standards and Technology (NIST) TES system, and 220 pixels are operated simultaneously with an energy resolution of 4 eV at 6 keV at a rate of ∼1 c/s pixel-1. The tolerance for high count rates is evaluated in terms of energy resolution and live time fraction, leading to an empirical compromise of ∼2 × 103 c/s (all pixels) with an energy resolution of 5 eV at 6 keV. By utilizing the TES's wideband spectroscopic capability, simultaneous multi-element analysis is demonstrated for a standard sample. We conducted x-ray absorption near-edge structure (XANES) analysis in fluorescence mode using the TES spectrometer. The excellent energy resolution of the TES enabled us to detect weak fluorescence lines from dilute samples and trace elements that have previously been difficult to resolve due to the nearly overlapping emission lines of other dominant elements. The neighboring lines of As Kα and Pb Lα2 of the standard sample were clearly resolved, and the XANES of Pb Lα2 was obtained. Moreover, the x-ray spectrum from the small amount of Fe in aerosols was distinguished from the spectrum of a blank target, which helps us to understand the targets and the environment. These results are the first important step for the application of high resolution TES-based spectroscopy at hard x-ray synchrotron facilities.

Association between myotonometric measurement of masseter muscle stiffness and maximum bite force in healthy elders.

BACKGROUND: Maximum bite force (MBF) is a common and useful index of masticatory function; it correlates with physical strength in elderly people. Palpation of stiffness in the masseter muscle during forceful biting has been considered to be associated with MBF. However, this assessment method relies on subjective judgments; no study has verified the relationship between MBF and quantitative measurements of masseter muscle stiffness (MMS). OBJECTIVE: We aimed to verify the association between masseter muscle myotonometric assessment results and MBF. METHODS: In total, 117 community-dwelling >65-year-old individuals from the Tokyo metropolitan area were assessed. MMS on the dominant side during forceful biting was measured with a MyotonPRO device. Masseter muscle thickness (MMT) during rest and forceful biting was measured with an ultrasonic diagnostic apparatus, and the difference in MMT (DMMT) between the rest and forceful biting conditions was determined. MBF data were obtained with a pressure-sensitive sheet and an associated device. To determine the independent variables affecting MBF and MMS, multivariate linear regression analyses with adjustments for age, sex and number of teeth were performed. RESULTS: The multivariate analysis revealed that MBF correlated with the number of teeth (ß = .489, P < .001) and MMS (ß = .259, P = .003) (R2  = .433). MMS correlated with MBF (ß = .308, P = .003) and DMMT (ß = .430, P < .001) (R2  = .326). CONCLUSION: Masseter muscle stiffness possibly reflects a force generated by the masseter muscle during forceful biting. Therefore, MMS is effective to assess tooth loss as well as an index of masseter muscle strength when evaluating MBF.

Relationship between displacement of the masseter muscle during biting and masseter muscle quality and bite force in healthy elderly persons.

BACKGROUND: Although age-related changes in muscle quality influence muscle strength, the relationship between masseter muscle (MM) quality and maximum biting force (MBF) has never been studied. OBJECTIVE: The aims of the study were to verify the relationship among MM quality, MBF, and the displacement of the MM while biting forcefully (MMD) and to clarify the age-related decline in MBF in healthy elderly persons. METHODS: Seventy-four healthy community-dwelling individuals (mean age, >65 years) from Tokyo metropolis were recruited. The thickness (index of muscle quantity), echo intensity (index of muscle quality) and displacement of the MM while biting forcefully (MMT, MMEI and MMD, respectively) were measured by ultrasonography. MBF was measured using a pressure-sensitive sheet. Independent predictors of MBF and MMD were determined using multivariate linear regression analyses adjusted for age, sex and the number of present teeth. RESULTS: MBF was significantly correlated with the number of teeth (ß = 0.577, P < .001) and MMD (ß = 0.302, P = .015), but not with MMT (ß = 0.019, P = .868) or MMEI (ß = 0.054 P = .703). MMD was significantly correlated with MMEI (ß = -0.606, P < .001), but not with MMT (ß = 0.048, P = .681) or the number of teeth (ß = 0.065, P = .613). CONCLUSIONS: MMEI was associated with MMD, an index of MBF, regardless of tooth number. The age-related quality change in the MM might cause a decrease in its contraction, resulting in age-related decline in MBF.