bluuebunny/crossref_metadata_2025 huggingface dataset:
Emotional Stress Triggers Intrahypothalamic But Not Peripheral Release of Oxytocin in Male Rats
Authors: Engelmann  , Ebner  , Landgraf  , Holsboer  , Wotjak
Published: March 2003

Previous experiments have shown that an exposure to defined stressors activates not only the ‘classical’ endocrine stress response but also the intrahypothalamic and peripheral release of oxytocin. In the present study we investigated the effects of an acute social defeat experience on the release of oxytocin within the hypothalamic supraoptic nucleus, just outside of the supraoptic nucleus toward the midline within the anterior ventro‐lateral part of the hypothalamus, and into plasma of adult male rats. Our results demonstrate that emotional stress triggers the release of oxytocin into the extracellular fluid of both the supraoptic nucleus and the anterior ventro‐lateral part of the hypothalamus (up to ≈320% and 170%, respectively). Interestingly, oxytocin release within the latter brain area, which is likely to originate from axons forming the hypothalamo‐neurohypophysial tract, was higher in absolute terms than that within the supraoptic nucleus itself, both under basal conditions and in response to social defeat. In contrast to intrahypothalamic release patterns, plasma oxytocin levels remained virtually unchanged upon stressor exposure. This demonstrates that the release of oxytocin within the hypothalamus is triggered by emotional stress. Furthermore, it indicates that under physiological conditions the release of oxytocin from the dendrites and somata upon axon terminals in the neurohypophysis is differentially regulated. Although not yet studied in detail, it may be hypothesized that the spatial and temporal release pattern of oxytocin is controlled by integrative neuronal networks at different brain levels (including hypothalamus and posterior pituitary) to ensure the appropriate involvement of this peptide in the stress response of the animal.
An Association of Elevated Serum Gonadotropin Concentrations and Alzheimer Disease?
Authors: Bowen  , Isley  , Atkinson
Published: March 2003

Alzheimer disease affects almost 4 million Americans and costs $65 billion annually. The disease is more common in women than in men, and studies suggest that oestrogen may have a protective effect. Oestrogen replacement lowers circulating concentrations of gonadotropins. When gonadotropins are added to rat granulosa cells in culture, the number of low density lipoprotein (LDL) receptors and the rate of uptake of low density lipoprotein increases. Many proteins found in Alzheimer disease plaques are ligands for low density lipoprotein receptors (LDLR) on central nervous system (CNS) neurones. This study evaluated whether gonadotropins may be associated with Alzheimer disease. Circulating concentrations of follicle stimulating hormone (FSH) and luteinizing hormone (LH) levels in 40 male residents of long‐term care facilities with the primary diagnosis of dementia were compared to 29 age‐matched controls. Serum concentrations of FSH and LH were significantly higher in dementia patients. We speculate they may play an aetiologic role in the deposition of abnormal proteins, particularly those associated with low density lipoprotein receptors, in CNS neurones.
Intracerebroventricular Administration of Melanin‐Concentrating Hormone Suppresses Pulsatile Luteinizing Hormone Release in the Female Rat
Authors: Tsukamura H. , Thompson R. C. , Tsukahara S. , Ohkura S. , Maekawa F. , Moriyama R. , Niwa Y. , Foster D. L. , Maeda K.‐I.
Published: March 2003

Melanin‐concentrating hormone (MCH) has been reported to be involved in the regulation of feeding behaviour in rats and mice. Because many neuropeptides that influence ingestive behaviour also regulate reproductive function, the present study was designed to determine if central administration of MCH changes pulsatile secretion of luteinizing hormone (LH) in the rats. Wistar‐Imamichi strain female rats were ovariectomized and implanted with oestradiol to produce a moderate inhibitory feedback effect on LH release. The effects of i.c.v. injections of MCH on LH release were examined in freely moving animals. Blood samples were collected every 6 min for 3 h through an indwelling cannula. After 1 h of sampling, MCH (0.1, 1 or 10 μg/animal) or vehicle (saline) was injected into the third cerebroventricle. Because MCH is also reported to affect the hypothalamo‐pituitary‐adrenal (HPA) axis, which in turn, can influence reproductive function, plasma corticosterone concentrations were determined in the same animals at 30‐min intervals during the first and last hours and every 12 min during the second hour of the 3‐h sampling period. When expressed as per cent changes, mean plasma LH concentrations after MCH administration were significantly lower in the animals injected with all doses of the peptide compared with vehicle‐treated animals; LH pulse frequency was significantly lowered by 1 μg of MCH. Per cent changes in mean plasma corticosterone levels were not significantly affected by MCH administration. These results in oestradiol‐treated ovariectomized rats indicate that central MCH is capable of inhibiting pulsatile LH secretion. We have previously shown that 48‐h fasting suppresses pulsatile LH release in the presence of oestrogen. Take together, these results raise the possibility that MCH could play a role in mediating the suppression of LH secretion during periods of reduced nutrition.
Voluntary Sucrose Ingestion, Like Corticosterone Replacement, Prevents the Metabolic Deficits of Adrenalectomy
Authors: Bell  , Bhatnagar  , Liang  , Soriano  , Nagy  , Dallman
Published: March 2003

We tested whether corticosterone replacement causes increased sucrose drinking in adrenalectomized (ADX) rats compared to sham‐ADX (sham) rats. ADX rats given high doses of corticosterone drank as much sucrose as sham rats, whereas at three lower doses of corticosterone, drinking was similar between groups and was only approximately 40% of that ingested by shams. Compared to sham rats, ADX rats drinking saline, or saline and saccharin, gain weight more slowly, contain less white adipose tissue, and have higher sympathetic outflow as assessed by uncoupling protein content in brown adipose tissue. Allowing sucrose as well as saline to drink restored all of these variables to normal in ADX rats with no‐ or low‐corticosterone. All endpoints from sucrose‐drinking ADX rats with no‐or low‐corticosterone were indistinguishable from those in water‐drinking shams. By contrast, sucrose‐drinking ADX rats that were given high doses of corticosterone exhibited the usual catabolic effects of corticosterone on body weight gain and, unlike sucrose‐drinking shams, were obese. We conclude that (i) high corticosterone stimulates the potability of sucrose and inhibits sympathetic stimulation of uncoupling protein; (ii) sucrose, without corticosterone, normalizes metabolic deficits in ADX rats probably through actions mediated both peripherally and by the central nervous system; and (iii) ADX rats have a distinct sucrose appetite.
Suppression of Adrenocorticotropic Hormone Release by Stimulation of the Nerve Fibres in the Anterior Pituitary
Authors: Gao L.‐Z. , Zhang W.‐H. , Ju G.
Published: March 2003

With the recent revelation of considerable peptidergic innervation of the anterior pituitary in several mammalian species, including man, it becomes imperative to elucidate the physiological significance of such a morphological entity. We addressed this issue by employing an anterior pituitary slice in vitro superfusion system coupled with electrical field stimulation. Anterior pituitary slices of 0.8 mm were perfused with Krebs‐Ringer bicarbonate–bovine serum albumin buffer in a superfusion chamber for 30 min before electrical field stimulation. A square current of 30 mA, 10 Hz and 0.5 ms was then applied for 10 min. The perfusate was collected every 10 min and measured for adrenocorticotropic hormone (ACTH) by radio‐immunoassay. It was found that under the experimental condition the basal release of ACTH was suppressed by electrical field stimulation of the nerve fibres in the anterior pituitary. Furthermore, vasopressin was added as a secretagogue. The suppression of ACTH by electrical field stimulation became even more marked. This is the first physiological evidence of the effect of stimulation of the nerve fibres innervating the anterior pituitary on its secretory activity.
Blunted Pituitary‐Adrenocortical Stress Response in Adult Rats Following Neonatal Dexamethasone Treatment
Authors: Felszeghy K. , Bagdy G. , Nyakas C.
Published: March 2003

Glucocorticoids have a prominent impact on the maturation of the stress‐related neuroendocrine system and on the postnatal establishment of adaptive behaviour. The present study aimed at investigating the stress responsiveness of the hypothalamo‐pituitary‐adrenocortical (HPA) axis in young and adult rats after neonatal treatment with the synthetic glucocorticoid agonist, dexamethasone. Newborn male Wistar rats were injected s.c. with 1 µg/g dexamethasone on postnatal days 1, 3 and 5. Circulating adrenocorticotropic hormone (ACTH) and corticosterone concentrations were measured in the resting state and following a 30‐min cold stress at the age of 10 days, as well as after a 30‐min restraint stress at the age of 14 weeks. Also in adults, pituitary and adrenocortical hormone responsiveness was evaluated after i.v. administration of 2 µg/kg corticotropin releasing hormone (CRH). In addition, glucocorticoid (GR) and mineralocorticoid receptor (MR) binding capacities were assessed in the pituitaries of adult rats. The results showed that at day 10 basal ACTH concentration was elevated while the cold stress‐evoked ACTH response was attenuated in the dexamethasone‐treated rats. As adults, treated rats showed a suppressed elevation of both ACTH and corticosterone plasma cncentrations in response to restraint, while basal hormonal concentrations were not altered. There was no difference in the magnitude of the CRH‐induced elevation of ACTH and corticosterone concentrations initially; however, the dexamethasone‐treated animals showed a prolonged secretion of both hormones. These animals also showed a selective decrease in pituitary GR binding capacity. Neonatal dexamethasone treatment strongly suppressed body weight gain, and adrenal and thymus weights in the early phase of postnatal development. By adulthood, the body and adrenal weights were normalized while thymus weight was greater than in controls. These findings indicate that neonatal dexamethasone treatment permanently alters HPA axis activity by reducing stress responses to cold and restraint probably through supra‐pituitary actions, and by decreasing the effectiveness of feedback through a diminished GR binding in the pituitary.
Selective Corticotropin‐Releasing Factor Type 1 Receptor Antagonist Blocks Conditioned Fear‐Induced Release of Noradrenaline in the Hypothalamic Paraventricular Nucleus of Rats
Authors: Otagiri A. , Wakabayashi I. , Shibasaki T.
Published: March 2003

The effects of conditioned fear on the release of noradrenaline in the hypothalamic paraventricular nucleus (PVN) and the involvement of corticotropin‐releasing factor (CRF) receptor type 1 (CRFR1) in conditioned fear‐induced changes in noradrenaline release were examined by intracerebral microdialysis in rats. Conditioned fear was produced by placing animals into a box where they had previously been exposed to a 5‐min period of electric footshock, 135 min prior to the start of experiment. Conditioned fear for 20 min produced a significant increase in the release of noradrenaline in the PVN. Intraperitoneal preadministration of a selective nonpeptidic CRFR1 antagonist, CRA1000, completely blocked the conditioned fear‐induced release of noradrenaline. These results suggest that CRFR1 is involved in the release of noradrenaline in the hypothalamic PVN induced by conditioned fear.
Systemic Administration of Ghrelin Induces Fos and Egr‐1 Proteins in the Hypothalamic Arcuate Nucleus of Fasted and Fed Rats
Authors: Hewson A. K. , Dickson S. L.
Published: March 2003

Ghrelin, a recently identified endogenous ligand for the growth hormone secretagogue (GHS) receptor, induces growth hormone (GH) secretion following systemic administration. We sought to determine whether systemic administration of ghrelin activates cells in the hypothalamic arcuate nucleus by examining the distribution of cells expressing Fos and Egr‐1 proteins. In normally fed rats, both ghrelin and GHRP‐6 (a synthetic GHS) significantly increased the number of cells expressing Fos and Egr‐1 in the arcuate nucleus. The effects of ghrelin and GHRP‐6 to induce Fos or Egr‐1 protein expression was significantly greater in fasted than in fed rats. Thus, we show that (i) ghrelin is a centrally active peptide; (ii) it acts in a similar manner to synthetic GHS; and (iii) its central actions are increased in fasting, presumably reflecting physiological changes that accompany altered food intake and/or nutritional state.
Differential Neuropeptide Responses to Starvation with Ageing
Authors: Kaneda T. , Makino S. , Nishiyama M. , Asaba K. , Hashimoto K.
Published: March 2003

During starvation, counterregulatory responses to loss of food (i.e. responses that lead to an increase in appetite) occur in the central nervous system (CNS). This study was designed to examine whether middle‐aged rats show greater or smaller behavioural, peripheral and central hormonal responses during starvation compared to young rats. In experiment 1, refeeding following 4 days of starvation was measured in both middle‐aged (72‐week‐old) and young (9‐week‐old) rats. The level of refeeding was similar to each prestarved level until 3 days after the end of starvation in both groups. From the 4th day, the level of refeeding in young rats increased and reached beyond the prestarved level, whereas refeeding in middle‐aged rats remained similar to the prestarved level. Thus, overall refeeding throughout 7 days was greater in young rats than in middle‐aged rats. In experiment 2, middle‐aged and young rats were starved for 4 days and were killed in the morning. Middle‐aged rats showed a smaller plasma corticosterone response than that of young rats. The magnitude of decreases in plasma glucose, insulin and leptin was similar in both groups. In the arcuate nucleus, the starvation‐induced increase in neuropeptide Y (NPY) mRNA and the decrease in proopiomelanocortin (POMC) mRNA were smaller in middle‐aged rats than in young rats. In contrast, the starvation‐induced decrease in corticotrophin‐releasing hormone (CRH) mRNA in the hypothalamic paraventricular nucleus was greater in middle‐aged rats than young rats. The magnitude of decrease in type‐2 CRH receptor mRNA in the ventromedial hypothalamus was similar in both groups. The results indicate that (a) ageing impaired refeeding response (b), middle‐aged rats showed the same directional neuropeptide mRNA responses as seen in young rats during starvation and (c) the magnitude of these counterregulatory responses in the CNS in middle‐aged versus young rats was not uniform, but rather was site‐specific or neuropeptide‐specific. This study suggests the importance of NPY and POMC responsiveness in the arcuate nucleus in the age‐related differences resulting from starvation‐induced refeeding.
Effects of Vasoactive Intestinal Polypeptide on Neurones of the Rat Suprachiasmatic Nuclei In Vitro
Authors: Reed H. E. , Cutler D. J. , Brown T. M. , Brown J. , Coen C. W. , Piggins H. D.
Published: March 2003

The suprachiasmatic nuclei (SCN) of the hypothalamus house the main circadian pacemaker in mammals. Vasoactive intestinal polypeptide (VIP) is the most abundant neuropeptide in the SCN and has been shown to phase‐shift the electrical activity rhythm of SCN cells in vitro. However, the effects of VIP on the cellular activity of rat SCN neurones are unknown. In this study, we examined the acute effects of VIP on the extracellularly recorded spontaneous firing rate of SCN neurones in an in‐vitro hypothalamic slice preparation. Furthermore, with the use of receptor‐selective agonists and antagonists, we determined which receptors might mediate the effects of VIP in the SCN. Approximately 50% of cells responded to VIP; the main type of response was suppression in firing rate, although a few cells were activated. Suppression responses to VIP were mimicked by the VPAC2 receptor agonist Ro 25‐1553 and blocked by the selective VPAC2 receptor antagonist PG 99‐465. The PAC1 receptor agonist maxadilan evoked responses from 40% of SCN cells, and activations to this agonist were not altered by PG 99‐465. Responses to VIP were not blocked by antagonists to ionotropic glutamate receptors, but the duration of suppression was modulated by the GABAA receptor antagonist bicuculline. Our data indicate that VIP alters the electrical activity of rat SCN neurones in vitro, via both VPAC2 and PAC1 receptors.
Changes in the Active Membrane Properties of Rat Supraoptic Neurones During Pregnancy and Lactation
Authors: Teruyama R. , Armstrong W. E.
Published: March 2003

To better understand the plasticity of intrinsic membrane properties of supraoptic magnocellular neuroendocrine cells associated with reproductive function, intracellular recordings were performed in oxytocin (OT) and vasopressin (VP) neurones from virgin, late pregnant (E19–22), and lactating (8–12 days of lactation) rats in vitro, using hypothalamic explants. OT neurones from virgin rats displayed a narrower spike width than neurones from pregnant and lactating rats, characterized by faster rise and decay times. Spike width changes in VP neurones were not as prominent as those observed in OT neurones. In OT neurones, the amplitude and the decay of the afterhyperpolarization following spike trains was significantly larger and faster, respectively, in pregnant and lactating rats compared to virgin rats. These properties did not change during pregnancy and lactation in VP neurones. The incidence of the depolarizing afterpotential following spikes significantly increased from approximately 20% in virgin rats to 40–50% during pregnancy and lactation in OT neurones, but was stable (80–90%) across states in VP neurones. Repetitive firing properties (frequency adaptation, the first interspike interval frequency and frequency‐current (F–I) relationship) were altered during pregnancy and lactation in OT neurones, but not VP neurones. The increased incidence of depolarizing afterpotentials in OT neurones enhances excitability, while the increased afterhyperpolarization results in suppression of firing rate. Thus, the changes may favour the short bursting activity seen in OT neurones during lactation. These results confirmed reproductive state‐dependent changes in intrinsic membrane properties of OT neurones during lactation, and suggest these changes are in place during late pregnancy. This argues that the plasticity in the electrical properties in OT neurones associated with lactation is not instigated by suckling.
Changes in the Arginine‐Vasopressin Immunoreactive Systems in Male Mice Lacking a Functional Aromatase Gene
Authors: Plumari L. , Viglietti‐Panzica C. , Allieri F. , Honda S. , Harada N. , Absil P. , Balthazart J. , Panzica G. C.
Published: March 2003

In male rodents, the arginine‐vasopressin‐immunoreactive (AVP‐ir) neurones of the bed nucleus of the stria terminalis (BNST) and medial amygdala are controlled by plasma testosterone levels (decreased after castration and restored by exogenous testosterone). AVP transcription in these nuclei is increased in adulthood by a synergistic action of the androgenic and oestrogenic metabolites of testosterone and, accordingly, androgen and oestrogen receptors are present in both BNST and medial amygdala. We used knockout mice lacking a functional aromatase enzyme (ArKO) to investigate the effects of a chronic depletion of oestrogens on the sexually dimorphic AVP system. Wild‐type (WT) and ArKO male mice were perfused 48 h after an i.c.v. colchicine injection and brain sections were then processed for AVP immunocytochemistry. A prominent decrease (but not a complete suppression) of AVP‐ir structures was observed in the BNST and medial amygdala of ArKO mice by comparison with the WT. Similarly, AVP‐ir fibres were reduced in the lateral septum of ArKO mice and but not in the medial preoptic area, a region where the AVP system is not sexually dimorphic in rats. No change was detected in the supraoptic and suprachiasmatic nuclei. However, a decrease in AVP‐ir cell numbers was however, detected in one subregion of the paraventricular nucleus. These data support the hypothesis that the steroid‐sensitive sexually dimorphic AVP system of the mouse forebrain is mainly under the control of aromatized metabolites of testosterone.
Implant anchored complete mandibular denture: evaluation of masticatory efficiency, oral function and degree of satisfaction
Authors: Pera  , Bassi  , Schierano  , Appendino  , Preti
Published: March 2003

Masticatory efficiency, oral function and degree of satisfaction with the treatment received were analysed in a group of fully edentulous patients with severe atrophy of the mandibular bone, rehabilitated with complete removable dentures, before and after anchoring the dentures to osseointegrated implants. Masticatory efficiency increased significantly and chewing cycles increased in amplitude after anchoring the denture. The component of the chewing cycle that most influenced the increase in functional area was the lateral one. A correlation was found between the increase in the lateral component of the chewing cycle and the increased masticatory efficiency achieved with implant‐anchored dentures. The degree of satisfaction with their rehabilitation reported by the subjects was correlated neither to increased masticatory efficiency nor to improved oral function.
The effect of light premature occlusal contact on tooth pain threshold in humans
Authors: Ikeda  , Nakano  , Bando  , Suzuki
Published: March 2003

The purpose of this study was to assess the influence of an experimentally induced light premature occlusal contact on tooth sensation. This assessment involved monitoring the electric tooth pain threshold (TPT) at multiple times before and after altering the occlusal contact. This alteration was produced by placing high inlays, which were measured with a custom made measuring device in maximum intercuspation. Data were collected on 10 teeth in 5 subjects, all whom were male and between the ages of 24 and 30 years. The contact area of the high inlays varied from 75 μm to 193 μm. The TPT changes in these teeth ranged from –43 to +21% of their baseline level. Seven of these teeth showed a significant decrease (P < 0.05) in the TPT, one showed an increase and two did not show a significant change. Two of the teeth with a decreased TPT had cold water triggered occlusal pain, and 2 teeth had only occlusal pain. After several inlay adjustments to eliminate interferance in maximum intercuspation, all tested teeth returned to their TPT baseline level and all symptoms disappeared. These results suggested that a light premature occlusal contact may change tooth sensation.
Subjective assessment of temporomandibular joint sounds
Authors: Prinz J. F.
Published: March 2003

If it could be shown that the human ear was sufficiently sensitive to describe TMJ sounds, there would be no need to use sophisticated electronic equipment to analyse the sounds. To test this, the ability of normal listeners to distinguish the subtle changes in position, pitch, duration and latency present in TMJ sounds is measured using triangle tests to determine the just‐noticeable differences. The results suggest that the human ear is a rather poor instrument for describing subtle differences in the position, duration and latency of TMJ sounds, but is capable of detecting small differences in frequency. It is therefore doubtful that the human ear can distinguish the reciprocal click associated with disc displacement with reduction from clicks due to defects of form on the basis of their relative position in the envelope of movement.
The periodontal response to cantilevered resin‐bonded bridgework
Authors: Rashid S. A. , Al‐Wahadni A. M. , Hussey D. L.
Published: March 2003

This study investigated 84 cantilevered resin‐bonded bridges (CRBB) in 60 patients. These CRBB (single retainer, single pontic) had been in place for an average of 43·6 months. Periodontal health was assessed on abutment teeth and contralateral control teeth. Periodontal indices utilized were Plaque Index (PI), Gingival Index (GI), Bleeding Index (BI), Pocket Depth (PD) and mobility. The marginal adaptation, the gingival extension of the retainers and the presence or absence of caries around each retainer margin were also assessed. Information about the history of debonding was collected and a success rate of 93% was reported. PI, GI and mean PD compared statistically significantly, less favourably, with scores of the control teeth. Marginal adaptation of the retainers was of a high standard and caries did not appear to be a problem.
Influence of myofunctional therapy on the perioral muscles. Clinical and electromyographic evaluations
Authors: Schievano D. , Rontani R. M. P. , Bérzin F.
Published: March 2003

The purpose of this study was to evaluate the influence of oral myofunctional therapy on the superior and inferior orbicularis oris (OOS and OOI) and mentalis (MT) muscles at rest and with lips closed in mouth breathing patients with no nasal airway obstruction. The sample consisted of 13 children aged 5–10 years. Clinical and electromyographic evaluations were performed before and after treatment. The results showed that muscles (P≪0·05) and functions (P≪0·01) improved after therapy, which can be observed by clinical evaluations. The electrical activity increase between rest and closed lip positions was statistically significant for the muscles studied. Before therapy the significant minimal level (s.m.l.) was P≪0·01 and after therapy it was P≪0·05. When the difference between the rest and closed lip positions before and after therapy was compared, a statistically significant decrease (P≪0·05) in the electrical activity of the OOI and MT muscles was observed. There was no correlation between the root‐mean‐square (RMS) of the OOI and MT muscles with the morphological and functional evaluations. The therapy can improve morphology and function of the muscles in mouth breathing patients with no nasal airway obstruction.
Posture correction as part of behavioural therapy in treatment of myofascial pain with limited opening
Authors: Komiyama O. , Kawara M. , Arai M. , Asano T. , Kobayashi K.
Published: March 2003

In this study, we applied cognitive behavioural intervention to subjects who had painful limited mouth opening, with or without posture correction in daily life. The efficacy of non‐intervention control was then compared with it in order to study the effectiveness of posture correction as part of a biobehavioural therapy. The visual analogue scale (VAS) value of pain intensity at maximum mouth opening and disturbance in daily life sharply declined in the group which received only cognitive behavioural intervention and those who received it together with posture correction in daily life compared to the non‐intervention control group although there was little difference between the intervention groups. Moreover, pain‐free unassisted mouth opening was restored earlier in the group which had added posture correction. This suggests that posture correction in daily life has a positive effect in alleviating myofascial pain with limited mouth opening.
Study on masticatory movement and its ability: efficacy of a test capsule in the evaluation of masticatory movement
Authors: Murai K. , Okimoto K. , Matsuo K. , Terada Y.
Published: March 2003

It has been shown that a test capsule originally designed as a simple and reliable aid to evaluate masticatory ability could help to identify the characteristics of chewing loops between individuals in evaluation of masticatory movement, and detect even a slight disorder in the stomatognathic system. In this study, the Sirognathograph® Analysing System was used to record and analyse mandibular movement with the test capsule and seven foods. In terms of total examination of the chewing rhythm, the test capsule showed a higher SX/SY ratio of chewing cycle duration (SX: variance between individuals, SY: variance between chewing loops of each person) than those of the comparative foods, excluding chewing gum. The coefficient of variation of the test capsule in the dimensions of the chewing path was lower than those of the comparative foods. Reverse and crossover patterns in chewing gum have been frequently observed in subjects with craniomandibular disorders. Subjects with a low frequency of such patterns in chewing gum tended to have a low frequency with the test capsule as well. Those with a high frequency in chewing gum tended to show such patterns with the test capsule more frequently.
Effect of eccentric clenching on mandibular deviation in the vicinity of mandibular rest position
Authors: Minagi S. , Ohmori T. , Sato T. , Matsunaga T. , Akamatsu Y.
Published: March 2003

Although the mechanical compression of the temporomandibular joint (TMJ), which could be caused by bruxism, would probably result in a slight change of the occlusal relationship, the effect of clenching in the eccentric mandibular position on the occlusal contact has not yet been clarified. This study aimed to investigate the effect of eccentric clenching on bilateral condylar position and thus to estimate any change of occlusal contact. Before and after voluntary clenching, with one third of the maximal voluntary clenching force, for 3 min at the canine edge‐to‐edge position, vertical deviation of the bilateral condyles was measured at the 1 mm open mandibular position. This was regulated by the three‐dimensional position of the anterior reference point which stands for the incisor point. The mean vertical displacement of the highly deviated side of the condyle was 141±55 μm, and the calculated mean displacement of the mandibular first molar region of the highly deviated side was 65±27 μm. From the results of this study, it was revealed that the eccentric clenching gave rise to three‐dimensional deviation of the mandible even when the mandible was in the vicinity of the rest position.
Effects of three concentrations of carbamide peroxide on the structure of enamel
Authors: Oltu Ü. , Gürgan S.
Published: March 2003

Carbamide peroxide bleaching agents have raised important questions on their potential adverse effects on the structure of enamel. The purpose of this study was to examine the effects of three carbamide peroxide bleaching agents in different concentrations (10, 16 and 35%) on the structure of enamel. Forty enamel slabs prepared from human third molars were divided equally among four groups. The specimens in the first and second group were subjected to 10% or 16% carbamide peroxide for 8 h per day for 6 weeks. Thirty‐five percent carbamide peroxide was applied to the third group for 30 min a day for a 4 day period according to the manufacturers recommendation. The fourth group served as the control and was kept in artificial saliva during the test period. At the completion of the treatment, all the specimens were examined by infrared absorbtion spectroscopy and X‐ray diffraction analysis. The results revealed that 10% or 16% carbamide peroxide did not seem to effect the structure of enamel, whereas 35% carbamide did affect the structure. The use of lower concentrations of carbamide peroxide (10–16%) is recommended over higher concentrations (35%) to avoid changes to the enamel.
Effect of the reducing agent on the oxygen‐inhibited layer of the cross‐linked reline material
Authors: Yatabe M. , Seki H. , Shirasu N. , Sone M.
Published: March 2003

The purpose of this study was to clarify the effect of the reducing agent on the oxygen‐inhibited layer of the cross‐linked reline material. A commercial autopolymerizing reline resin containing 1,6‐hexanediol dimethacrylate as cross‐linking agent and 1 wt.% sodium sulphite solution as a reducing agent was prepared. The inhibited layer was observed using an optical transmission microscope under the conditions of the application of sodium sulphite for 0, 1, 5 and 15 min after curing for 10 min in air. As a control, the reline material was cured on sealing from air. Moreover, the three‐point flexural strength test was performed under the same conditions. The fracture was then observed using scanning electron microscopy (SEM). Although hardness of the inhibited layer was enhanced after the application of the reducing agent, the layer was still observed. The flexural strength of the control and the groups after application of the reducing agent was significantly higher than the group without reducing agent. SEM examination revealed many polymer beads on the group without reducing agent, whereas polymer beads could not be observed on the groups applying the reducing agent. These results indicated that the application of sodium sulphite was effective in hardening the surface unpolymerized zone.
Effect of mixing method on rheological properties of alginate impression materials
Authors: Inoue K. , Song Y. X. , KamiunteN O. , Oku J. , Terao T. , FujiI K.
Published: March 2003

The apparent viscosity of alginate impression paste prepared by three mixing methods (hand‐mixing technique (HM), semiautomatic instrument (SM) and automatic mixing instrument (AM)), and the gel strength and surface depression of the respective set materials were measured. The materials used were eight commercially available products mixed at a temperature of 23 ± 0.5 °C and allowed to set. The AM had a high mixing speed, which reduced the working time 4.4–31.5%, compared with HM. This was the result of an increase in paste temperature during mixing. In the case of impression materials mixed with the AM, the gel strength and the surface depression at the gel fracture increased significantly, in accordance with Fisher's protected least significant difference (PLSD) analysis. This phenomenon is caused by a decrease of air bubbles in the set material.
A histomorphometric analysis on bone dynamics in denture supporting tissue under continuous pressure
Authors: Imai Y. , Sato T. , Mori S. , Okamoto M.
Published: March 2003

The purpose of this study was to investigate bone dynamics under a denture base, in relation to the intensity of continuous pressure exerted through it to the denture supporting tissue. Two hundred and fifty male rats of Wistar strain were divided into five groups, four of which wore experimental dentures to load continuous pressure of 0·0, 1·0, 10·0 or 20·0 kPa to the molar region of the hard palate. The fifth group was the non‐denture‐wearing group. Fluorescent labelled palatal bone tissue was stained with Villanueva bone stain and was prepared for the undecalcified grinding section. In the 0·0 kPa group whose mucosa was covered with denture base, although no bone resorption was observed, bone formation was inhibited up to 4 weeks after the denture insertion. Bone dynamics in the 1·0 kPa group was similar to those in the 0·0 kPa group. In the 10·0 and 20·0 kPa groups, bone resorption was observed until 3 and 2 weeks after the denture insertion, and the amount of bone resorption (AoBR) was 24 ± 17 and 35 ± 21 lm, respectively. After bone resorption in these groups, although osteoid formation increased earlier than 0·0 kPa group, mineralization showed a similar time course with 0·0 kPa group. In conclusion, bone dynamics under a denture base caused by continuous pressure exerted through it was revealed to show a time course depending on the intensity of the initial pressure. Amount of bone resorption was also revealed to correspond to the intensity of the initial pressure. Bone formation following bone resorption did not cause equivalent recovery of the bone surface level to the level observed in the case without bone resorption.
Oral hygiene habits, denture cleanliness, presence of yeasts and stomatitis in elderly people
Authors: Kulak‐Ozkan Y. , Kazazoglu E. , Arikan A.
Published: March 2003

The purpose of this study was to determine oral hygiene habits, denture cleanliness, presence of yeasts and denture stomatitis in elderly people. Seventy complete denture wearers were investigated clinically and mycologically. Subjects were evaluated according to, presence of denture stomatitis, presence of yeasts, denture cleanliness, frequency of denture brushing and denture cleaning methods. Swabs were taken from the palate investigated mycologically in order to identify the yeast colonies. No statistical relationship was found between denture stomatitis and frequency of denture brushing and denture cleaning methods. However, there was a statistically significant relationship between denture stomatitis, yeasts' presence and denture cleanliness.
Relationship between functional disc position and mandibular displacement in adolescent females: posteroanterior cephalograms and magnetic resonance imaging retrospective study
Authors: Nakagawa S. , Sakabe J. , Nakajima I. , Akasaka M.
Published: March 2003

The purpose of this study was to investigate the relationship between the disc positions of temporomandibular joints (TMJ), the vertical and lateral mandibular displacement (VMD and LMD, respectively) and age in female adolescents with signs and symptoms of the temporomandibular disorders (TMD). The VMD and LMD were assessed, using posteroanterior (PA) cephalograms. The disc positions were assessed by magnetic resonance imaging (MRI) and categorized as follows: normal disc position, functional disc displacement and functional disc dislocation. Excluding patients with osteoarthritis, the total number of subjects was 54 female adolescents who were grouped into three: the bilateral normal disc position group, the unilateral or bilateral functional disc displacement group, and the unilateral or bilateral functional disc dislocation group. We compared the extent of VMD and LMD between the three groups, and investigated their correlation with age. Results indicate that functional disc displacement and dislocation are related to mandibular displacement, and VMD did not correlate with age but LMD did correlate with age. This study suggests that the onset of disc displacement is related to the mandibular displacement and disturbs normal growth of the mandible three‐dimensionally.
Raman scattering determination of the depth of cure of light‐activated composites: influence of different clinically relevant parameters
Authors: Leloup G. , Holvoet P. E. , Bebelman S. , Devaux J.
Published: March 2003

The purpose of this research was to determine the depth of cure of light‐activated composites in relation with different clinically relevant parameters. A Raman spectroscopic method has been used. The measurement of cure is made on a relative basis by comparing the vibration band of the residual unpolymerized methacrylate C=C bond at 1640 cm–1 against the aromatic C=C stretching band at 1610 cm–1 used as an internal standard. The information gained draw attention to the importance of light transmission during the exposure. The influence of sample's thickness on the depth of cure is illustrated by a second order polynomial regression. The shade and translucency of the resin composite also modify the light transmission and thus have a significant influence on the degree of conversion. Moreover the light‐source intensity and the distance from the curing tip are important parameters of influence. A significant reduction of the depth of cure is observed for all sample thickness of resin composite tested when using a light device with an intensity of 300 mW cm–2 as well as using a distance from the curing tip higher than 20 mm.
Complications and failures in removable partial dentures: a clinical evaluation
Authors: Saito M. , Notani K. , Miura Y. , Kawasaki T.
Published: March 2003

The design of removable partial dentures (RPDs) is an important factor for good prognostications. The purpose of this study was to clarify the effectiveness of denture designs and to clarify the component that had high rates of failure and complications. A total of 91 RPDs, worn by 65 patients for 2–10 years, were assessed. Removable partial dentures were classified into four groups: telescopic dentures (TDs), ordinary clasp dentures (ODs), modified clasp dentures (MDs) and combination dentures (CDs). The failure rates of abutment teeth were the highest and those of retainers were the second highest. The failure rates of connectors were generally low, but they increased suddenly after 6 years. Complication and failure rates of denture bases and artificial teeth were generally low. Complication and failure rates of TDs were high at abutment teeth and low level at retainers. Complication and failure rates of ODs were high at retainers.
DTG thermal analyses and viscosity measurements of three commercial agar impression materials
Authors: Taira M. , Araki Y.
Published: March 2003

Three commercial agar impression materials, two for clinical uses and one for dental laboratory, were examined for their thermal properties by differential thermogravimetric (DTG) thermal analyses and viscosity measurements. On DTG profiles, an endothermic peak along with weight loss at around 100 °C was observed on all three agar impression materials as a result of water evaporation. Two clinical agar impression materials were more susceptible to this trend than the remaining one dental laboratory agar impression material. The viscosity of three agar impression materials could be expressed in the exponential function of temperature. Viscosity at 46 °C of one dental laboratory agar impression material far exceeded those of two clinical agar impression materials. Monitoring the viscosity could facilitate the detailed analysis of setting process of agar impression materials upon cooling, and might be useful for future development of agar‐based dental impression materials.
Fluoride release and uptake characteristics of aesthetic restorative materials
Authors: Attar N. , Önen A.
Published: March 2003

Summary The aims of this study were firstly to investigate the fluoride‐releasing characteristics of two composite resins (Tetric and Valux Plus), two polyacid‐modified resin composites (Compoglass and Dyract), and conventional glass–ionomer cement (Ceramfil β). The second aim was to assess the fluoride uptake and subsequent release from the same range of materials. Fifteen discs (6 mm diameter and 1·5 mm height) were prepared for each material. Each disc was immersed in 4 ML of deionized water within a plastic vial. The release of fluoride was measured daily at 1, 2, 3, 4, 5, 15, 30 and 60 days. After daily fluoride release was measured for 60 days, samples were refluoridated in 1000‐ppm sodium fluoride (NaF) solutions (pH 6·6) for 10 min and fluoride release was measured daily for a total of 5 days. The release of fluoride from aesthetic restorative materials was measured by using specific fluoride electrode and an ionanalyser. Results were statistically analysed by two‐way repeated measure ANOVA and Duncan's multiple range test. The results revealed that all fluoride‐containing materials (Ceramfil β, Compoglass, Dyract, Tetric) released fluoride initially and the release was greatest at the first day. At any time during the test period Ceramfil β released the most and Valux Plus did not release any detectable fluoride (P < 0·01). Sample exposures to 1000 ppm NaF solution increased the 24‐h fluoride release from all fluoride‐containing materials. This difference lasted only 24–48 h after exposure. Ceramfil β had a tendency to recharge not seen with the other materials (P < 0·05).
Localization of TMJ sounds to side
Authors: Widmalm S. E. , Williams W. J. , Ang B. K. , Mckay D. C.
Published: March 2003

summary  Differential diagnosis depends in cases with disk displacement on accurate identification of sound source. Mistakes may occur when clicking from one temporomandibular joint (TMJ) is heard on both sides of the head at auscultation and neither examiner nor patient, is sure about side. The hypothesis was that the head tissues affect spectral characteristics of TMJ sounds and that differences due to different positioning of sensors can be used in localization of source. The aim was to compare bilateral electronic recordings of unilateral TMJ sounds to obtain and compare attenuation, phase shift and time delay. Recordings were made from 12 subjects with unilateral clicking. Small electret condenser microphones, bandwidth 40–20 000 Hz, were placed at the openings of the auditory canals and the sounds were recorded at a sampling rate of 48 000 Hz. The head tissues acted as a filter causing a frequency dependent attenuation and phase shift. There was a time difference between the ipsi‐ and the contra lateral recordings, the latter always having a longer delay time (range 0·2–1·2 ms, group mean 0·68 ms, s.d. 0·292 ms). In conclusion, spectral analysis of bilateral electronic TMJ sound recordings is of diagnostic value when bilateral clicking is heard at auscultation and can help to avoid diagnosing a silent joint as clicking.
Fluoride uptake and development of artificial erosions in bleached and fluoridated enamel in vitro
Authors: BURGMAIER G.‐M. , SCHULZE I. M. , ATTIN T.
Published: March 2003

Summary The aim of the present in vitro study was to evaluate the effect of carbamide peroxide (CP) bleaching on fluoride uptake in enamel. Additionally, the susceptibility for erosion in bleached and fluoridated enamel was tested. Each four enamel specimens were prepared from 44 bovine incisors. The four samples gained from each tooth were distributed among four groups (A–D) of 44 specimens each: A: (unbleached/unfluoridated) served for determination of baseline fluoride concentration; B: (unbleached/fluoridated) four times in 2000 ppm NaF solution (2 min); C: (bleached/unfluoridated) four times in 10% CP (8 h); D: (bleached/fluoridated) four times in 10% CP and fluoridation. In 22 specimens of each group both KOH‐soluble and structurally bound fluoride were determined in the outermost 30 μm of the enamel. In the remaining specimens erosions were induced by immersing the samples in 5 mL of 1% citric acid (20 min) and microhardness was evaluated before and after demineralization. Statistical analysis showed that KOH‐soluble fluoride uptake was similar for group B and D specimens. Structurally bound fluoride uptake after fluoride application in unbleached samples was significantly higher than in bleached ones. Bleaching only resulted in a highly significant fluoride loss. In all samples erosion caused a significant microhardness loss. The study showed that pre‐treatment of enamel with CP followed by fluoridation does not improve erosive resistance. Moreover the study reveals that CP treatment decreases concentration of structurally bound fluoride in enamel which could not be outweighed by fluoridation with 2000 ppm NaF. It is concluded that it is not feasible to improve fluoride uptake in enamel with a pre‐treatment with 10% CP.