Mechanical and frictional properties of aesthetic orthodontic wires obtained by hard chrome carbide plating.

Background/purpose: Although aesthetic wire coating has been increasing in demand, it has problems that changes in mechanical properties and increase in frictional force. The aim of this study was to evaluate the coating of the wire, as characterized by aesthetics, in terms of low and constant friction and mechanical properties.

Materials And Methods: Hard chrome carbide-plated (HCCP) wires (HCCP group), commercially available polymer-coated wires (P group), rhodium-coated wires (R group), and uncoated wires (control group) were used.

Mechanical properties of orthodontic wires covered with a polyether ether ketone tube.

Objectives: To evaluate the esthetics and frictional force of an orthodontic wire passed through a newly designed tube made of a polyether ether ketone (PEEK) resin.

Materials And Methods: Two types of standard PEEK tubes were prepared at 0.5 × 0.

Combination of chewing and stress up-regulates hippocampal glucocorticoid receptor in contrast to the increase of mineralocorticoid receptor under stress only.

In general, acute immobilization stress increases plasma corticosterone levels that signal the hypothalamic-pituitary-adrenal axis. Mineralocorticoid receptors and glucocorticoid receptors in the hippocampus perform crucial roles in this feedback mechanism. In the present study, we investigated the effects of chewing under stress on the rat hippocampal mineralocorticoid and glucocorticoid receptors by immunohistochemistry.

Chewing ameliorates stress-induced suppression of spatial memory by increasing glucocorticoid receptor expression in the hippocampus.

Chewing alters hypothalamic-pituitary-adrenal axis function and improves the ability to cope with stress in rodents. Given that stress negatively influences hippocampus-dependent learning and memory, we aimed to elucidate whether masticatory movements, namely chewing, improve the stress-induced impairment of spatial memory in conjunction with increased hippocampal glucocorticoid receptor expression. Male Sprague-Dawley rats were subjected to restraint stress by immobilization for 2h: the stress with chewing (SC) group were allowed to chew on a wooden stick during the latter half of the immobilization period, whereas the stress without chewing (ST) group were not allowed to do so.

Effects of mandibular deviation on brain activation during clenching: an fMRI preliminary study.

Using functional magnetic resonance imaging (fMRI) in eight healthy human subjects, the present study measured blood oxygenation level-dependent (BOLD) signals during clenching in a malocclusion model, using a custom-made splint that forced the mandible to a retrusive position and a splint of no modification for control, and compared the results to the BOLD signals during the corresponding resting conditions. An individual visual analog scale (VAS) score was also examined during clenching to evaluate the interactions between fMRI data and psychiatric changes. During both clenchings, activations in four brain regions (premotor cortex, prefrontal cortex, sensorimotor cortex, and insula) were seen.

Chewing rescues stress-suppressed hippocampal long-term potentiation via activation of histamine H1 receptor.

We have previously found in rats that chewing, an active behavioral strategy to cope with a stressful situation, rescues long-term potentiation (LTP) in the hippocampus through activating stress-suppressed N-methyl-D-aspartate (NMDA) receptor function. To further examine the mechanisms underlying this ameliorative effect of chewing, we studied the involvement of the histaminergic system, which has been shown to be activated by mastication, in the LTP of hippocampal slices of rats that were allowed to chew a wooden stick during exposure to immobilization stress. Chewing failed to rescue stress-suppressed LTP in the rats treated with histamine H1 receptor (H1R) antagonist pyrilamine (5 mg/kg, i.

Nitric oxide levels in rat hypothalamus are increased by restraint stress and decreased by biting.

Mastication, which includes biting, is of great importance not only for the intake of food but also for the mental, physical and physiological functioning of the body. For example, biting suppresses the stress response. Although biting and nitric oxide (NO) appear to modulate brain dynamics during stress, the underlying mechanisms have not been elucidated.

Measurement of oxidative stress in the rodent brain using computerized electron spin resonance tomography.

The strategy of this study was to improve the electronic spin resonance (ESR) application used to detect free radical-induced oxidative stress in animal models. We have developed an in vivo ESR imaging system with high-quality ESR-computed tomography (CT) images by using a nitroxyl spin probe--BBB-permeable, 3-methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine-1-yloxy (MC-PROXYL)--in living small animals. We first measured the distribution of MC-PROXYL in the head region of a living mouse by using ESR-CT imaging after treatment with MC-PROXYL.

Biting reduces acute stress-induced oxidative stress in the rat hypothalamus.

We investigated the inhibitory effect of para-masticatory activity, namely biting, on restraint stress-induced oxidative stress. A blood brain barrier-permeable nitroxyl spin probe, 3-methoxycarbonyl-2,2,5,5,-tetramethylpyrrolidine-1-oxyl (MC-PROXYL), was administered to rats and L-band electron spin resonance (ESR) and ESR-computerized tomography (ESR-CT) imaging were used to show that the decay rate constant of MC-PROXYL in the hypothalamus of isolated brain after 30 min of restraint stress was more rapid than in unrestrained control rats, suggesting that restraint was associated with oxidative stress. Interestingly, biting during restraint stress caused the decay rate constant of MC-PROXYL in isolated brain to approach that of the control group.