Effect of Mastication Muscle Activity on Prefrontal Cortex NIRS Measurement: A Pilot Study.

Changes in NIRS signals are related to changes in local cerebral blood flow or oxy-Hb concentration. On the other hand, recent studies have revealed the effect of chewing gum on cognitive performance, stress control etc. which accompanied brain activity in the prefrontal cortex (PFC).

Masseter Muscle Activity in Track and Field Athletes: A Pilot Study.

Teeth clenching has been shown to improve remote muscle activity (by augmentation of the Hoffmann reflex), and joint fixation (by decreased reciprocal inhibition) in the entire body. Clenching could help maintain balance, improve systemic function, and enhance safety. Teeth clenching from a sports dentistry viewpoint was thought to be important and challenging.

Relationships Between Gum-Chewing and Stress.

Studies have shown that chewing is thought to affect stress modification in humans. Also, studies in animals have demonstrated that active chewing of a wooden stick during immobilization stress ameliorates the stress-impaired synaptic plasticity and prevents stress-induced noradrenaline release in the amygdala. On the other hand, studies have suggested that the right prefrontal cortex (PFC) dominates the regulation of the stress response system, including the hypothalamic-pituitary-adrenal (HPA) axis.

Influence of Pleasant and Unpleasant Auditory Stimuli on Cerebral Blood Flow and Physiological Changes in Normal Subjects.

The prefrontal cortex (PFC) plays an important role in emotion and emotional regulation. The valence asymmetry hypothesis, proposes that the left/right asymmetry of the PFC activity is correlated with specific emotional responses to stressors. However, this hypothesis still seems to leave room for clarifying neurophysiological mechanisms.

Effect of clenching with a mouthguard on head acceleration during heading of a soccer ball.

Concussions are acceleration-deceleration injuries that occur when biomechanical forces are transmitted to the cerebral tissues. By limiting acceleration of the head, enhanced cervical muscle activity derived from clenching with a mouthguard (MG) may reduce the incidence or severity of concussions following impact. The purpose of this study was to investigate the effect of voluntary clenching with a proper MG on acceleration of the head during "heading" of a soccer ball.

Thinning factors influence on custom-made mouthguards thermoforming.

The aim of this study was to clarify and quantify factors influencing thinning during a thermoforming using a special simulation model that has three different flat surfaces such as 0 degree, 45 degree and 90 degree against a pressurizing force. Air pressure type samples were made by EVA and acrylic resin blank. Vacuum type samples were also made by EVA.

Influence of different post-core systems on impact stress: a pilot study.

Unlabelled: This pilot study compared impact strain at the core and root surfaces between two different post-core systems.

Materials And Methods: The form of a bovine mandibular front tooth was modified to resemble that of a human maxillary incisor as a test specimen. A cast post and core (Metal PC) and composite resin and glass fiber-reinforced epoxy resin post (Fiber-Resin PC) system were tested.

Does clenching reduce indirect head acceleration during rugby contact?

Background: Concussions are common among athletes, with the potential to cause memory-related, physical, cognitive, emotional, and behavioral damage. A concussion is an acceleration/deceleration injury resulting from direct and indirect biomechanical forces transmitted to the cerebral tissues. From a sports dentistry viewpoint, increased mastication muscle activity or clenching due to the presence of a mouthguard may enhance cervical muscle activity, thereby reducing damage following impact.

Shock absorption ability of mouthguard against forceful, traumatic mandibular closure.

Background: The positive effects of wearing a mouthguard on shock absorption have been indicated in various papers. The ability of a mouthguard to protect against indirect injury, however, is not clear, and the thickness that a mouthguard would require to provide such protection remains to be determined. The primary aim of this study was to clarify the shock absorption potential of a mouthguard against forced, traumatic occlusion.

Paired maxillary and smaller mandibular mouthguard for rugby player with malalignment.

A rugby player who had frequently experienced soft tissue injuries while playing rugby and wearing a conventional custom-made mouthguard came to the hospital clinic. The patient had suffered traumatic soft tissue injuries such as lip lacerations and bite trauma. Severe crowding due to ectopic maxillary and mandibular canines was observed.

Effects of occlusal disharmony on working memory performance and prefrontal cortex activity induced by working memory tasks measured by NIRS.

The effects of artificial occlusal disharmony (AOD) on working memory function and prefrontal cortex (PFC) activity in the elderly were examined. We evaluated working memory function using the modified Sternberg test (ST). We measured activity in the bilateral PFC during ST using near-infrared spectroscopy (NIRS) before and after AOD: the mandibular position was displaced by a splint for 10 min.

Effects of experimentally deviated mandibular position on stress response.

The purpose of this study was to investigate the effects of stress on -prefrontal cortex (PFC), emotion (using visual analogue scale, VAS, and State-Trait Anxiety Inventory, STAI), and the autonomic nervous system (ANS). Two types of stress were applied: (1) malocclusion-induced physical stress and (2) mental stress induced by an arithmetic task. Malocclusion was induced using an experimentally deviated mandibular device (EDMD) to obtain an experimentally deviated mandibular position (EDMP).

Easy fabrication of a new type of mouthguard incorporating a hard insert and space and offering improved shock absorption ability.

The positive effects of wearing a mouthguard have been indicated in various epidemiological surveys and experiments, and their usage appears to be increasing in many sports. However, many preventable sports-related dental injuries still occur even with the use of a conventional mouthguard. We have developed a mouthguard (the Hard & Space mouthguard) with sufficient injury prevention ability (more than 95% shock absorption ability against impact with a steel ball carrying 15.

Effect of experimental horizontal mandibular deviation on dynamic balance.

Purpose: There are two aspects of human balance: static balance and dynamic balance. However, to the author's knowledge, no studies have investigated how changes in the stomatognathic system influence dynamic balance. This aim of this study was to determine the effect of horizontal mandibular deviation on stability of upright posture on an unstable platform in order to clarify the relationship between the stomatognathic system and the dynamic balance.

Influence of pre-laminated material on shock absorption ability in specially designed mouthguard with hard insert and space.

Purpose: We have developed a new type of laminated mouthguard, the Hard & Space mouthguard, which incorporates a hard material insert and a space to prevent contact between the mouthguard and the buccal surfaces of the teeth. The purpose of this study was to investigate the effect of this new design on shock absorption.

Methods: Three types of mouthguard (a conventional laminated EVA mouthguard and two 3-layer type "Hard & Space" mouthguards made of 1.

Functional near-infrared spectroscopy study on primary motor and somatosensory cortex response to biting and finger clenching.

The purpose of this study was to compare the influence of biting and finger clenching intensity on the concentration of oxygenated hemoglobin (OxyHb) in regional cerebral blood flow (rCBF) as an indicator of brain activity in the primary motor (MI) and somatosensory (SI) cortices. Functional near-infrared spectroscopy (fNIRS) was used in 8 healthy subjects. Subjects were required to do biting (bite) and finger clenching (fclench) at 20, 50 and 80% of maximum force.

Activity in the premotor area related to bite force control--a functional near-infrared spectroscopy study.

The purpose of this study was to elucidate the influence of bite force control on oxygenated hemoglobin (OxyHb) levels in regional cerebral blood flow as an indicator of brain activity in the premotor area. Healthy right-handed volunteers with no subjective or objective symptoms of problems of the stomatognathic system or cervicofacial region were included. Functional near-infrared spectroscopy (fNIRS) was used to determine OxyHb levels in the premotor area during bite force control.

Expression of myosin heavy-chain mRNA in cultured myoblasts induced by centrifugal force.

Ballistic muscle training leads to hypertrophy of fast type fibers and training for endurance induces that of slow type fibers. Numerous studies have been conducted on electrical, extending and magnetic stimulation of cells, but the effect of centrifugal force on cells remains to be investigated. In this study, we investigated the effect of stimulating cultured myoblasts with centrifugal force at different speeds on cell proliferation and myosin heavy-chain (MyHC) mRNA expression in muscle fiber.

Functional near-infrared spectroscopy study on primary motor and sensory cortex response to clenching.

The purpose of this study was to elucidate the influence of clenching and clenching intensity on oxygenated hemoglobin (OxyHb) levels in regional cerebral blood flow as an indicator of brain activity in the primary motor and sensory cortices. Functional near-infrared spectroscopy (fNIRS) was used to minimize the effect of clenching-associated muscle activity in eight healthy subjects. Subjects were required to clench at 20%, 50% and 80% of maximum clenching force.

Are all mouthguards the same and safe to use? Part 2. The influence of anterior occlusion against a direct impact on maxillary incisors.

The purpose of this study was to clarify the influence anterior occlusion, of mouthguards, has on protecting against a direct collision to the maxillary anterior teeth. In other words, the support mandibular dentition has when wearing a mouthguard. Two types of mouthguards were used for this study, one with an appropriate anterior occlusion or a mouthguard with positive anterior occlusion (MGAO+) and another which was a single-layer mouthguard lacking the same occlusion or a mouthguard with negative anterior occlusion (MGAO-) but with the same thickness on the buccal side.

In search of necessary mouthguard thickness. Part 1: From the viewpoint of shock absorption ability.

Purpose: To date, the minimum thickness required for a mouthguard has been assumed to be around 2 mm to 4 mm. However, this figure is based mostly on experience and is yet to be standardized. The purpose of this study is to determine the minimum thickness required to obtain sufficient energy absorption.

A vacuum technique to increase anterior thickness of athletic mouthguards to achieve a full-balanced occlusion.

A full-balanced occlusion is essential for mouthguards. It has been reported that a balanced occlusion for upper and lower anterior teeth is essential for prevention of injuries occurring to the maxillary anterior teeth and alveolar bone caused by horizontal direct impact. The support of the mandibular teeth through the mouthguard is critical to prevent maxillary front tooth injury from a direct impact force.

Effects of stretching stimulation with different rates on the expression of MyHC mRNA in mouse cultured myoblasts.

In vivo studies have shown that changes in the characteristics of skeletal muscle fiber are determined by type of exercise or training. These earlier studies on mechanical stimulation, however, have all employed stimulation applied at a constant intensity, and no studies appear to have investigated change with variation of intensity of stimulation. In this study, we investigated the characteristics and differentiation of myoblasts stretched at different rates.

Adhesive strength and its improvement referring to the laminated-type mouthguard.

The manufacture of laminated-type mouthguards requires skill in fusing sheets of mouthguard materials together. Adequate adhesive strength is required to use mouthguards in a stable condition for a long time. Therefore, in this study, the exfoliation test was applied and some treating techniques and conditions that improve the adhesive strength on a laminated surface were examined.

[Problems and possibility of resin abutment construction with a combined use of fiber posts: at the beginning of discussion].

When using post materials that are more rigid than teeth for abutment construction, tooth root fracture may be caused by stress concentration in the remaining part of the tooth root. Most of the tooth root fractures clinically observed in metal post abutment cases are longitudinal fractures, resulting in tooth extraction in many cases. In cases with sufficient coronal tooth substance, post-less abutment construction has recently been considered.