Takafumi Kato

Osaka University | Handai · Department of Oral Physiology

Study Objectives The present study investigated the hypothesis that subjects with primary sleep bruxism (SB) exhibit masseter and cortical hyperactivities during quiet sleep periods that are associated with a high frequency of rhythmic masticatory muscle activity (RMMA). Methods Fifteen SB and ten control participants underwent polysomnographic re...

This longitudinal study investigated developmental changes in jaw-closing muscle activities during ingestive behaviors in rats. On postnatal day (P) 10, electromyography (EMG) electrodes were inserted into the masseter and temporalis muscles of rat pups. EMG activities were recorded for the following ingestive behaviors between P14 and P49: for suc...

Purpose: The present study investigated the relationship between sleep bruxism (SB) and obstructive sleep apnea (OSA) in relation to the sleep architecture. Methods: We conducted a cross-sectional study. Polysomnographic recordings were performed on 36 patients. Sleep, respiratory, and oromotor variables, such as rhythmic masticatory muscle acti...

Background: Sleep on the first night in a sleep laboratory is characterized by a lower sleep quality and frequency of rhythmic masticatory muscle activity (RMMA) than that on the second night in moderate to severe sleep bruxism (SB) patients. Objective: The aims of this study was to clarify the physiological factors contributing to the first nig...

Background: Sleep bruxism (SB), an oral behavior in otherwise healthy individuals, is characterized by frequent rhythmic masticatory muscle activity (RMMA) during sleep. RMMA/SB episodes occur over various sleep stages (N1-N3 and rapid eye movement (REM)), sleep cycles (non-REM to REM), and frequently with microarousals. It currently remains uncle...

Background Malocclusion is a multifactorial condition associated with genetic and environmental factors. The purpose of this study was to investigate the prevalence of occlusal traits, oral habits, and nose and throat conditions by age and to assess the association between malocclusion and its environmental factors in Japanese preschool children....

Rhythmic masticatory muscle activity (RMMA) is a periodic muscle activity that characterises sleep bruxism (SB) events. These can occur as a single event, in pairs, or in clusters. Since RMMA episodes often occur in clusters and the relevance of this occurrence is unknown, we conducted a study to investigate the effect of RMMA clusters on sleep fra...

Sleep quality can be affected by several factors, such as sleep environment, lifestyles and so on. This research proposed a novel deep learning architecture with multiple-factors for sound-based sleep quality assessment. Utilizing sleep sound for sleep quality evaluation is low-cost and contactless, also, sound data can reflect several physical beh...

Background: Dental caries is one of the most common chronic diseases worldwide, affecting lifelong as well as children. Therefore, it is important to clarify factors related to early childhood caries (ECC) in a younger population in terms of caries prevention. However, the prevalence of ECC is low in developed countries in the twenty-first century...

This exploratory observational study aimed to evaluate whether the blood levels of serotonin and enzymes involved in serotonin synthesis are associated with sleep breathing parameters. A total of 105 patients were included in this study, who were subjected to single-night polysomnography with simultaneous audio–video recordings. Peripheral blood sa...

Sleep quality assessment as an indicator of daily health care plays an important role in our physiological and mental activity. Sound during sleep contains rich information on biological activities, such as body movement, snoring, and sleep bruxism. However, sound features differ depending on individual and environmental differences. In order to de...

Background Dental caries is one of the most common chronic diseases worldwide, affecting lifelong as well as children. Therefore, it is important to clarify factors related to early childhood caries (ECC) in a younger population in terms of caries prevention. However, the prevalence of ECC is low in developed countries in the 21st century and a lar...

Background Malocclusion is a multifactorial condition associated with genetic and environmental factors. The purpose of this study was to investigate the prevalence of occlusal traits, oral habits, and nose and throat conditions by age and to assess the association between malocclusion and its environmental factors in Japanese preschool children. M...

Background: Sleep bruxism (SB) is a common sleep disorder that affects approximately 20% of children and 10% of adults. It may cause orodental problems, such as tooth wear, jaw pain, and temporal headaches. However, the pathophysiological mechanisms underlying SB remain largely unknown, and a definitive treatment has not yet been established. Hig...

Background Malocclusion is a multifactorial condition associated with genetic and environmental factors. The purpose of this study was to investigate the prevalence of occlusal traits, oral habits, and nose and throat conditions by age and to assess the association between malocclusion and its environmental factors in Japanese preschool children....

The P2Y2 receptor agonist, diquafosol sodium, is commonly used to treat the signs and symptoms of dry eye disease (DE) patients. Although diquafosol improves tear film stability, the neural mechanisms underlying the reduction in ocular pain are not well defined. This study determined if repeated application of diquafosol reduces the sensitization o...

Objective This paper aims to present and describe the Standardised Tool for the Assessment of Bruxism (STAB), an instrument that was developed to provide a multidimensional evaluation of bruxism status, comorbid conditions, aetiology and consequences. Methods The rationale for creating the tool and the road map that led to the selection of items i...

Parkinson's disease (PD) causes multiple non-motor symptoms as well as distinctive motor deficits. It is well known that chemosensory and mild cognitive impairments frequently occur in the early stage of PD, but the mechanisms underlying these PD-related prodromal impairments remain unknown. We examined whether intranasal rotenone-administrated mal...

This study examined whether subjective and objective sleep parameters (sleep stage, electroencephalography [EEG] power, heart rate variability) are related to the progression of sleep cycles using differences in the variables between two nights. We hypothesized that the association between night-to-night differences between subjective and objective...

Purpose: To assess (1) whether the occlusal splint (OS) or mandibular advancement splint (MAS) allowed the best quality of sleep and was most comfortable; and (2) the relationship of sleep quality and comfort with the reduction in rhythmic masticatory muscle activity (RMMA) related to sleep bruxism (SB). Materials and methods: Polysomnographic d...

Dental sleep medicine as a discipline was first described about a quarter of a century ago. Snoring, obstructive sleep apnea, sleep bruxism, xerostomia, hypersalivation, gastroesophageal reflux disease, and orofacial pain were identified as dental sleep-related conditions. This scoping review aimed to: i) identify previously unidentified dental sle...

Study objectives: This study investigated the diagnostic accuracy of Sleep Profiler, which relies on ambulatory polysomnography (PSG) with electroencephalogram for sleep bruxism (SB) and examined its episode-by-episode agreement in comparison to PSG equipped with audio-visual recordings (avPSG). Methods: This prospective two-gate study recruited...

Background Sleep spindles play a crucial role in multiple neuronal network functions. Initiation and termination of spindles are regulated by the thalamic reticular nucleus and thalamocortical network, and spindle can be an index for brain organization. We conducted a preliminary study of the parameters of sleep spindles, focusing on sleep-stage te...

Introduction: During sleep, limb and jaw muscle motor activity can be quantified by electromyography (EMG). The frequency of periodic limb activity during sleep increases with age in both the general and clinical research populations. The literature is controversial regarding stability, over age, of the frequency of rhythmic masticatory muscle act...

Patients with persistent and severe dry eye disease (DED) have corneal hypersensitivity, resulting in ocular pain, and diquafosol sodium, a potent P2Y2 receptor agonist, is commonly used to improve the resultant tear film stability. This study determined the effects of diquafosol instillation on the suppression of trigeminal subnucleus caudalis (Vc...

Oral feeding is critical for survival in both humans and animals. However, few studies have reported quantitative behavioral measures associated with the development of oral feeding behaviors. Therefore, the present study investigated developmental changes in the oral feeding behaviors of rats by quantitatively assessing pasta eating and licking be...

Background: Taste impairments are often accompanied by olfactory impairments in the early stage of Parkinson's disease (PD). The development of animal models is required to elucidate the mechanisms underlying taste impairments in PD. Objective: This study was conducted to clarify whether the intranasal administration of rotenone causes taste imp...

Proprioceptive sensory information from muscle spindles is essential for the regulation of motor functions. However, little is known about the motor control regions in the cerebellar cortex that receive proprioceptive signals from muscle spindles distributed throughout the body, including the orofacial muscles. Therefore, in this study, we investig...

Objectives: The purpose of this study was to investigate the prevalence of occlusal traits, oral habits, and nose and throat conditions by age and to assess the association between malocclusion and its environmental factors in preschool children. Materials and Methods: A total of 503 healthy children (258 boys and 245 girls aged 3–6 years) were rec...

Objectives Sleep bruxism (SB) is associated with physiological activities including sympathetic autonomic system dominance and sleep micro-arousal. While oral appliances (OA) are used to prevent SB harmful effects, the influence of OAs physiological mechanisms during sleep is unknown. The aim of this study is to assess whether heart rate variabilit...

Parkinson's disease (PD) characteristically presents with multiple symptoms as well as distinctive motor impairments. Smell disorders, followed by mild cognitive impairment, frequently occur in the early stage of PD, and both are progressed as motor symptoms. To elucidate the mechanisms underlying these prodromal symptoms, the development of approp...

Objectives The FTO gene has been reported as an obesity-associated gene and is also considered a risk gene for osteoarthritis (OA). However, its exact function is unclear, and there is conflicting evidence on the involvement of FTO polymorphisms in OA via obesity. The purpose of this study was to determine the effects of FTO polymorphism rs8044769...

Objective The areas of the amygdala contributing to rhythmic jaw movements and the movement patterns induced remain unknown. Therefore, the present study investigated the areas of the amygdala contributing to rhythmic jaw movements using repetitive electrical microstimulation techniques. Design Experiments were performed on head-restrained guinea...

Tongue function is regarded as a primary factor in the etiology of malocclusion, but details of the relationship remain unknown. The purpose of the present study was to investigate maximum tongue pressure, in preschool children to examine its relationship with dental occlusion. A total of 477 healthy children (248 boys, 229 girls, aged 4–6 years) w...

This study investigated the effects of acute footshock stress (FS) on the occurrence of rhythmic masticatory muscle activity (RMMA) during sleep in guinea pigs. Animals were prepared for chronic recordings from electroencephalogram, electrooculogram and electromyograms of neck and masseter muscles. The signals were recorded for six hours on the two...

Obstructive sleep apnea (OSA), characterized by low arterial oxygen saturation during sleep, is associated with an increased risk of orofacial pain. In this study, we simulated chronic intermittent hypoxia (CIH) during the sleep/rest phase (light phase) to determine the role of transient receptor potential vanilloid 1 (TRPV1) in mediating enhanced...

Purpose: The aims of the present study were to investigate the temporal relationships between jaw and bodily movements and clarify motor processes in the genesis of rhythmic masticatory muscle activity (RMMA) in sleep bruxism (SB). Methods: Video-polysomnography recordings were obtained from ten subjects with SB (mean age: 23.4 ± 1.6 years) and ten...

It has been reported that rhythmic jaw movements (RJMs) spontaneously occur in ketamine-anesthetized animals. The present study investigated the physiological processes that occur during the cortical, cardiac, and respiratory events which contribute to the genesis of RJMs in animals after supplemental ketamine injections. Fourteen guinea pigs were...

Study Objectives The present study aimed to clarify the physiological relationships between rhythmic masticatory muscle activity (RMMA) and cyclic changes in cortical, autonomic, and arousal-motor activities during sleep in sleep bruxism (SB) children. Methods Polysomnographic recordings were performed on fifteen SB children (9 boys, 6 girls, 10.3...

A recent report from the European Sleep Research Society’s task force “Beyond AHI” discussed an issue that has been a long‐term subject of debate – what are the best metrics for obstructive sleep apnoea (OSA) diagnosis and treatment outcome assessments? In a similar way, sleep bruxism (SB) metrics have also been a recurrent issue for >30 years and...

Objective The aim of the present study was to characterize the cyclic sleep processes of sleep-stage dynamics, cortical activity, and heart rate variability during sleep in the adaptation night in healthy young adults. Methods Seventy-four healthy adults participated in polysomnographic recordings on two consecutive nights. Conventional sleep vari...

Objectives Deterioration of lip function in the elderly is a form of oral hypofunction. It is important to understand age-related changes in lip function to improve oral health. This study aimed to quantitatively compare the maximum lip-closing force (LCF) and the ability to control LCF during voluntary lip-pursing movements between elderly and you...

The pesticide rotenone inhibits mitochondrial complex I and is thought to cause neurological disorders such as Parkinson’s disease and cognitive disorders. However, little is known about the effects of rotenone on conditioned taste aversion memory. In the present study, we investigated whether intranasal administration of rotenone affects condition...

Background: Healthy sleep is important not only for physical health but also brain development in children. Several reports have pointed out that Japanese adults and children have later bedtimes and shorter sleep times compared to those in other countries, possibly because of Japanese culture and lifestyles. Therefore, an intervention tool suitabl...

Although numerous systems for sleep quality assessment are available on the market nowadays, they usually fail due to two main reasons. First, their sleep quality assessment is not based on scientific evidence. Second, many of these systems require additional hardware to identify the sleep state, thus becoming expensive and impractical. We address...

Objective This study investigated the first night effect on the polysomnographic diagnosis of sleep bruxism (SB). Methods Polysomnographic recordings were performed for two consecutive nights in forty-three subjects (mean age 23.7 ± 0.32 years [range: 20.0 - 33.0]). Sleep variables and rhythmic masticatory muscle activity (RMMA) were scored for tw...

It becomes increasingly clear that some sleep disorders have important diagnostic and/or management links to the dental domain, hence the emergence of the discipline ‘Dental Sleep Medicine’. In this review, the following topics are discussed: 1. the reciprocal associations between orofacial pain and sleep; 2. the associations between sleep bruxism...

Study objectives: The present study aimed to investigate the occurrence and characteristics of apnea-hypopnea events in young non-obese healthy Japanese participants. Methods: One hundred and three young adult participants without sleep complaints (M:56; F:47; age: 24.5 ± 3.0 years; BMI: 20.9 ± 1.8 kg/m²) underwent two-night polysomnography (PSG...

Neuropathic pain is characterized by sensory abnormalities, such as mechanical allodynia and heat hyperalgesia, associated with alteration in the peripheral and central nervous systems. After trigeminal nerve injury, phenotypic changes that involve the expression of calcitonin gene-related peptide occur in large- and medium-sized myelinated neurons...

Cortical pyramidal neurons show rapid and irreversible membrane depolarization in response to oxygen-glucose depolarization (OGD). In this study, we investigated cellular mechanisms responsible for rapid depolarization caused by OGD in layer III pyramidal neurons of the mouse somatosensory cortex. When OGD solution was perfused in the presence of C...

The typical manifestation of sleep bruxism (SB) is the presence of repetitive jaw muscles activity over the sleep period, with or without tooth grinding. SB is present in otherwise healthy subjects and in association to psychological or medical conditions, indispensable for dentists to optimize their management planning based on the differential di...

Study objectives: We hypothesized that sleep stage dynamics are different in patients with sleep bruxism (SB) and that these changes are associated with the occurrence of rhythmic masticatory muscle activity (RMMA). Methods: Fifteen healthy controls and 15 patients with SB underwent overnight polysomnography. Sleep variables and survival curves...

Purpose: Rhythmic masticatory muscle activity (RMMA), a biomarker of sleep bruxism (SB), has been associated with mild hypoxia and/or big breaths in some adults with non-sleep-disordered breathing. The purpose of this study was to investigate that concurrent oxygen and carbon dioxide fluctuations are among the physiological variables that contribu...

Recent studies have developed simple techniques for monitoring and assessing sleep. However, several issues remain to be solved for example high-cost sensor and algorithm as a home-use device. In this study, we aimed to develop an inexpensive and simple sleep monitoring system using a camera and video processing. Polysomnography (PSG) recordings we...

Aims: To investigate the objective and subjective characteristics of sleep and psychosomatic and physiologic variables in young subjects with different frequencies of rhythmic masticatory muscle activity (RMMA) during sleep. Methods: A total of 54 young (mean age 23.8 ± 2.1 years), healthy subjects underwent polysomnographic (PSG) recordings for...

Background It is considered important to evaluate the ability to control lip‐closing force (LCF). Objective This study aimed to investigate the ability to control directional LCF. Methods The experimental system included an apparatus developed to measure LCF during lip pursing in eight directions (upper, lower, right, left and the four directions...

Rhythmic jaw muscle activities frequently occur during non‐rapid eye movement sleep in patients with sleep bruxism. The present study aimed to investigate the response characteristics of the masticatory rhythm generation during non‐rapid eye movement sleep in animals. Eleven guinea pigs were surgically prepared for polygraphic recordings by electro...

In 2013, consensus was obtained on a definition of bruxism as repetitive masticatory muscle activity characterised by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible and specified as either sleep bruxism or awake bruxism. In addition, a grading system was proposed to determine the likelihood that a certain assessme...

The occlusal vertical dimension (OVD) in guinea pigs is maintained by tooth eruption and grinding. It has been reported that the experimentally raised OVD recovers to the innate OVD within a few days in guinea pigs. However, the mechanisms underlying OVD adjustment are not entirely understood. This study thus aimed to clarify whether the experiment...

Purpose: Concomitant occurrence of respiratory events can be often overlooked in the clinical practice of SB. This study assessed physiological characteristics of rhythmic masticatory muscle activity (RMMA) and concomitant respiratory events in young SB subjects asymptomatic to obstructive sleep apnea (OSA). Methods: Twenty-two subjects (age: 24...

A good sleep is important for a healthy life. Recently, several consumer sleep devices have emerged on the market claiming that they can provide personal sleep monitoring; however, many of them require additional hardware or there is a lack of scientific evidence regarding their reliability. In this paper we proposed a novel method to assess the sl...

Little is known about how proprioceptive signals arising from muscles reach to higher brain regions such as the cerebral cortex. We have recently shown that a particular thalamic region, the caudo-ventromedial edge (VPMcvm) of ventral posteromedial thalamic nucleus (VPM), conveys the proprioceptive signals from jaw-closing muscle spindles (JCMSs) i...

Rhythmic masticatory muscle activity can be a normal variant of oromotor activity, which can be exaggerated in patients with sleep bruxism. However, few studies have tested the possibility in naturally sleeping animals to study the neurophysiological mechanisms of rhythmic masticatory muscle activity. This study aimed to investigate the similarity...