bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth Hormone Secretagogue Activation of the Arcuate Nucleus and Brainstem Occurs Via a Non‐Noradrenergic Pathway
Authors: Bailey  , Von Englehardt  , Leng  , Smith  , Dickson
Published: March 2003

Noradrenergic systems are integrally involved in the release of growth hormone (GH) from the anterior pituitary gland and in regulating the activity of hypothalamic growth hormone‐releasing hormone (GHRH) neurones. GH secretagogues act at both the pituitary and the hypothalamus to facilitate the release of GH. In male rats, using the induction of Fos protein as an indicator of neuronal activation, we examined whether neurones in the brainstem, the main noradrenergic input to the hypothalamus, were activated by systemic administration of peptide and non‐peptide GH secretagogues. In addition, we examined the effects of chronic central noradrenaline depletion upon GH secretagogue‐induced activation of the arcuate nucleus. Systemic injection of the GH secretagogues, GHRP‐6 and MK‐0677 induced Fos protein expression in a population of area postrema cells, but less than 10% of these cells were noradrenergic. Depletion of hypothalamic noradrenaline by the specific neurotoxin, 5‐ADMP, did not alter GH secretagogue‐induced activation of Fos protein in the arcuate nucleus compared to vehicle‐treated controls. We conclude that the central actions of GH secretagogues involve the activation of non‐noradrenergic cells in the area postrema and that GH secretagogue‐induced activation of the arcuate nucleus occurs independently of noradrenergic tone.
Vasopressin Preferentially Depresses Excitatory Over Inhibitory Synaptic Transmission in the Rat Supraoptic Nucleus In Vitro
Authors: Kombian  , Mouginot  , Hirasawa  , Pittman
Published: March 2003

Endogenous arginine‐vasopressin (AVP) in the supraoptic nucleus is known to decrease the firing rate of some supraoptic nucleus neurones. To determine a possible mechanism by which this locally released AVP produces this change in neuronal excitability, we investigated the effects of AVP on evoked excitatory (e.p.s.c.) and inhibitory post‐synaptic (i.p.s.c.) responses recorded in magnocellular neurones in a hypothalamic slice preparation, using the perforated‐patch recording technique. Our data show that AVP produces a dose‐dependent decrease in the evoked e.p.s.c. in about 80% of magnocellular neurones tested with an estimated EC50 of about 0.9 μM. The maximum decrease in e.p.s.c. amplitude was about 31% of control and was obtained with an AVP concentration of 2 μM. The AVP‐induced synaptic depression was blocked by Manning Compound (MC), a non‐selective antagonist of oxytocin (OXT) and vasopressin (AVP) receptors, but not by a selective OXT receptor antagonist. It was not mimicked by desmopressin (ddAVP), a V2‐receptor subtype agonist. By contrast, AVP used at the same concentration (2 μM), had no global effect on pharmacologically isolated i.p.s.c.s in the majority of magnocellular neurones tested. These results show that AVP acts in the supraoptic nucleus to reduce excitatory synaptic transmission to magnocellular neurones by activating a non‐OXT receptor, presumably the V1 receptor subtype.
Localization and Physiological Regulation of the Exocytosis Protein SNAP‐25 in the Brain and Pituitary Gland of Xenopus laevis
Authors: Kolk  , Nordquist  , Tuinhof  , Gagliardini  , Thompson  , Cools  , Roubos
Published: March 2003

In mammals, the synaptosomal‐associated protein of 25 kDa, SNAP‐25, is generally thought to play a role in synaptic exocytosis of neuronal messengers. Using a polyclonal antiserum against rat SNAP‐25, we have shown the presence of a SNAP‐25‐like protein in the brain of the South‐African clawed toad Xenopus laevis by Western blotting and immunocytochemistry. Xenopus SNAP‐25 is ubiquitously present throughout the brain, where its distribution in various identified neuronal perikarya and axon tracts is described. Western blot analysis and immunocytochemistry also demonstrated the presence of SNAP‐25 in the neural, intermediate and distal lobes of the pituitary gland. Intensity line plots of confocal laser scanning microscope images of isolated melanotropes indicated that SNAP‐25 is produced and processed in the rough endoplasmatic reticulum and Golgi apparatus, and is associated with the plasma membrane. Immunoelectron microscopy substantiated the idea that SNAP‐25 is present in the plasma membrane but also showed a close association of SNAP‐25 with the bounding membrane of peptide‐containing secretory granules in both the neurohemal axon terminals in the neural lobe and the endocrine melanotropes in the intermediate lobe. Quantitative Western blotting revealed that adapting Xenopus to a dark background has a clear stimulatory effect on the expression of SNAP‐25 in the neural lobe and in the melanotrope cells. This background light intensity‐dependent stimulation of SNAP‐25 expression was confirmed by the demonstration of increased immunofluorescence recorded by confocal laser scanning microscopy of individual melanotropes of black background‐adapted toads. On the basis of this study on Xenopus laevis, we conclude that SNAP‐25 (i) plays a substantial role in the secretion of a wide variety of neuronal messengers; (ii) functions in the central nervous system but also in neurohormonal and endocrine systems; (iii) acts at the plasma membrane but possibly also at the membrane of synaptic vesicles and peptide‐containing secretory granules; (iv) acts not only locally (as in synapses), but at various sites of the plasma membrane (as in the endocrine melanotrope cell); and (v) can be upregulated in its expression by physiological stimuli that increase the extent of the molecular machinery involved in exocytosis.
Effects of Chronic Oestrogen Replacement on Stress‐Induced Activation of Hypothalamic‐Pituitary‐Adrenal Axis Control Pathways
Authors: Dayas C. V. , Xu Y. , Buller K. M. , Day T. A.
Published: March 2003

Oestrogen replacement therapy reportedly suppresses hypothalamic‐pituitary‐adrenal (HPA) axis responses to an emotional stressor in postmenopausal women. However, most studies in the rat suggest a facilitatory role for oestrogen in the control of HPA axis function. One explanation for this difference may be the regimen of oestrogen replacement: during oestrogen replacement therapy, oestrogen levels are low and constant whereas most animal studies examined the HPA axis response when oestrogen levels are rising. In the present study, we assessed HPA axis stress responses in mature ovariectomized rats after plasma oestrogen levels had been maintained at physiological levels for a prolonged period (25 or 100 pg/ml for 7 days). In the case of both an emotional stressor (noise) and a physical stressor (immune challenge by systemic interleukin‐1β administration), oestrogen replacement suppressed stress‐related Fos‐like immunolabelling, in hypothalamic neuroendocrine cells and plasma adrenocorticotropin hormone responses. From the present data, and past reports, it appears unlikely that these effects of oestrogen are due to a direct action on corticotropin‐releasing factor or oxytocin cells. Therefore, to obtain some indication of oestrogen's possible site(s) of action, Fos‐like immunolabelling was mapped in the amygdala and in brainstem catecholamine groups, which are neuronal populations demonstrating substantial evidence of involvement in the generation of HPA axis stress responses. In the amygdala, oestrogen replacement suppressed central nucleus responses to immune challenge, but not to noise. Amongst catecholamine cells, oestrogen replacement was more effective against responses to noise than immune challenge, suppressing A1 and A2 (noradrenergic) and C2 (adrenergic) responses to noise, but only A1 responses to immune challenge. These data suggest that, as in postmenopausal women on oestrogen replacement therapy, chronic low‐level oestrogen replacement can suppress HPA axis stress responses in the rat. Moreover, oestrogen appears to exert effects at multiple sites within putative HPA axis control pathways, even though most of the relevant neuronal populations do not contain genomic receptors for this gonadal steroid and the pattern of oestrogen action differs for an emotional vs a physical stressor.
Thyroid Hormones Regulate Pituitary Growth Hormone Secretagogue Receptor Gene Expression
Authors: Kamegai J. , Tamura H. , Ishii S. , Sugihara H. , Wakabayashi I.
Published: March 2003

Thyroid hormones regulate growth hormone (GH) secretion by actions both at the hypothalamus and at the pituitary gland. At the level of the pituitary, thyroid hormones increase GH and GH‐releasing hormone receptor (GHRH‐R) mRNA expression. To test if thyroid hormones might also regulate the pituitary expression of mRNA for the recently identified GH secretagogue (GHS) receptor, GHS‐R, primary pituitary cell cultures from adult male rats were treated with triiodothyronine (T3) and GHS‐R mRNA levels were assessed by reverse transcriptase‐polymerase chain reaction. T3 increased pituitary GHS‐R mRNA levels in a dose‐ and time‐dependent manner. The stimulatory action of T3 on GHS‐R mRNA levels was also observed in the presence of the RNA synthesis inhibitor, actinomycin D, indicating that gene transcription is not required. Closer examination of the decay rates of GHS‐R mRNA in the presence of actinomycin D revealed T3 extended the half‐life of the GHS‐R mRNA from 8 h (basal) to15 h, demonstrating that T3 increases GHS‐R mRNA levels in vitro by increasing message stability.
Oestradiol Microimplants in the Ventromedial Preoptic Area Inhibit Secretion of Luteinizing Hormone via Dopamine Neurones in Anoestrous Ewes
Authors: Anderson G. M. , Connors J. M. , Hardy S. L. , Valent M. , Goodman R. L.
Published: March 2003

Oestradiol exerts a season‐specific negative feedback effect on the GnRH/LH neurosecretory system of the Suffolk ewe. This neuroendocrine suppression is mediated in part by dopamine A15 neurones, but these neurones do not possess the oestrogen receptor. Based on indirect evidence, we hypothesized that oestrogen receptor‐containing neurones in the ventromedial preoptic area (vmPOA) may be the initial step in a neuronal system whereby oestradiol suppresses GnRH secretion during the non‐breeding season. To test this, three experiments were conducted using ovariectomized ewes receiving either empty or oestradiol‐containing bilateral microimplants directed at the vmPOA or s.c. subcutaneous oestradiol‐containing implants. In the first experiment, LH pulse frequency was measured on days 0, 1, 7 and 14 of treatment during seasonal anoestrus. In vmPOA oestradiol and s.c. oestradiol groups only, LH pulse frequency was suppressed on days 7 and 14, with maximal suppression evident by day 7. In the second experiment, this protocol was repeated during the breeding season, with LH pulses examined on days 0 and 7; LH pulse frequency did not change in any group. The third experiment tested if the effect of vmPOA oestradiol during anoestrus could be overcome by an injection of the dopamine‐D2 receptor antagonist (–)‐sulpiride. The vmPOA microimplants and s.c. oestradiol implants again suppressed LH pulse frequency and this was reversed by sulpiride in vmPOA oestradiol ewes. We conclude that oestradiol acts on cells in the vmPOA to stimulate a system involving dopamine neurones that inhibits GnRH/LH pulsatility in the anoestrous ewe.
Functional Cross‐Talk Between the Hypothalamic‐Pituitary‐Gonadal and ‐Adrenal Axes
Authors: Viau V.
Published: March 2003

Under normal conditions, the adrenal glucocorticoids, the endproduct of the hypothalamic‐pituitary‐adrenal (HPA) axis, provide a frontline of defence against threats to homeostasis (i.e. stress). On the other hand, chronic HPA drive and glucocorticoid hypersecretion have been implicated in the pathogenesis of several forms of systemic, neurodegenerative and affective disorders. The HPA axis is subject to gonadal influence, indicated by sex differences in basal and stress HPA function and neuropathologies associated with HPA dysfunction. Functional cross‐talk between the gonadal and adrenal axes is due in large part to the interactive effects of sex steroids and glucocorticoids, explaining perhaps why several disease states linked to stress are sex‐dependent. Realizing the interactive nature by which the hypothalamic‐pituitary‐gonadal and HPA systems operate, however, has made it difficult to model how these hormones act in the brain. Manipulation of one endocrine system is not without effects on the other. Simultaneous manipulation and assessment of both endocrine systems can overcome this problem. This dual approach in the male rat reveals that testosterone can act and interact on different aspects of basal and stress HPA function. Basal adrenocorticotropic hormone (ACTH) release is regulated by testosterone‐dependent effects on arginine vasopressin synthesis, and corticosterone‐dependent effects on corticotropin‐releasing hormone (CRH) synthesis in the paraventricular nucleus (PVN) of the hypothalamus. In contrast, testosterone and corticosterone interact on stress‐induced ACTH release and drive to the PVN motor neurones. Candidate structures mediating this interaction include several testosterone‐sensitive afferents to the HPA axis, including the medial preoptic area, central and medial amygdala and bed nuclei of the stria terminalis. All of these relay homeostatic information and integrate reproductive and social behaviour. Because these modalities are affected by stress in humans, a dual systems approach holds great promise in establishing further links between the neuroendocrinology of stress and the central bases of sex‐dependent disorders, including psychiatric, cardiovascular and metabolic disease.
Comparison Between the Influence of the Intravenous and Intracerebroventricular Injection of a Nitric Oxide Donor on Adrenocorticotropic Hormone Release and Hypothalamic Neuronal Activity
Authors: Seo D. O. , Lee S. , Rivier C.
Published: March 2003

We investigated the ability of the nitric oxide (NO) donor 3‐morpholino‐sydnonimine (SIN‐1) to release adrenocorticotropic hormone (ACTH) and up‐regulate hypothalamic neurones following its intravenous (i.v.) injection. i.v. SIN‐1 (0.2–1.8 mg/kg) produced dose‐related increases in plasma ACTH levels which were blocked by prior neutralization of endogenous corticotropin‐releasing factor (CRF) but not by vasopressin antibodies. In contrast, the intracerebroventricular (i.c.v.) injection of 50‐µg SIN‐1 released significantly larger amounts of ACTH, a response blunted by either CRF or vasopressin antibodies. While i.c.v. SIN‐1 markedly up‐regulated transcripts of the immediate early gene NGFI‐B in the paraventricular nucleus (PVN) of the hypothalamus, no such response was observed following the i.v. injection of up to 2.0 mg/kg SIN‐1. Finally, we found no evidence that the influence of the peripheral administration of SIN‐1 on ACTH secretion is mediated by altered pituitary responsiveness to CRF or vasopressin. The fact that NO has a profound hypotensive influence in the periphery suggests that it may have released ACTH through this mechanism, although the absence of PVN neuronal response in regions that are activated by decreased blood pressure casts some doubt on this hypothesis. As the systemic injection of arginine derivatives that block NOS activity potently augment the ACTH response to circulating pro‐inflammatory cytokines or vasopressin, the present findings indicate that the mechanisms responsible for this phenomenon are distinct from those responsible for ACTH released by i.v. SIN‐1.
Suppression of Pulsatile Luteinizing Hormone Secretion but Not Luteinizing Hormone Surge in Leptin Resistant Obese Zucker Rats
Authors: Todd B. J. , Ladyman S. R. , Grattan D. R.
Published: March 2003

The adipose tissue‐derived hormone leptin may be a primary mediator linking nutritional status and reproduction. The present study used the leptin‐resistant obese female Zucker rat to investigate whether leptin signalling is required for normal pulsatile luteinizing hormone (LH) secretion and/or generation of the LH surge. For the pulsatile LH secretion study, an indwelling atrial catheter was implanted and a low dose of oestrogen given as a subcutaneous implant to lean and obese ovariectomized (OVX) Zucker rats. One week following OVX, blood samples were collected every 10 min for 3 h during the morning. Plasma LH concentrations were measured by radioimmunoassay. For the LH surge study, lean and obese OVX rats were given a high dose of oestrogen as a subcutaneous implant. Two days later, rats were given progesterone at 09.00 h to induce a proestrus‐like LH surge. Blood samples were collected from an indwelling atrial catheter throughout that and the following day and plasma LH concentrations were measured by radioimmunoassay. LH pulse amplitude and mean LH secretion were profoundly attenuated in obese Zucker rats compared with lean littermates, whereas LH pulse frequency was not significantly different between phenotypes. The opioid receptor antagonist naloxone did not affect the pattern of pulsatile LH secretion in obese rats, suggesting that leptin does not exert its facilitatory effects on LH secretion through an opioidergic pathway. Both lean and obese rats showed characteristic steroid‐induced LH surges. It therefore appears that a leptin signal is required for generation of a normal pattern of pulsatile LH secretion, but is not a necessary component of the steroid‐induced LH surge.
Opioid Receptor Subtypes Involved in the Regulation of Prolactin Secretion During Pregnancy and Lactation
Authors: Andrews Z. B. , Grattan D. R.
Published: March 2003

Afferent endogenous opioid neuronal systems facilitate prolactin secretion in a number of physiological conditions including pregnancy and lactation, by decreasing tuberoinfundibular dopamine (TIDA) inhibitory tone. The aim of this study was to investigate the opioid receptor subtypes involved in regulating TIDA neuronal activity and therefore facilitating prolactin secretion during early pregnancy, late pregnancy and lactation in rats. Selective opioid receptor antagonists nor‐binaltorphimine (κ‐receptor antagonist, 15 µg/5 µl), beta funaltrexamine (μ‐receptor antagonist, 5 µg/5 µl) and naltrindole (δ‐receptor antagonist, 5 µg/5 µl) or saline were administered intracerebroventricularly (i.c.v.) on day 8 of pregnancy during a nocturnal prolactin surge, on day 21 of pregnancy during the ante partum prolactin surge or on day 7 of lactation before the onset of a suckling stimulus. Serial blood samples were collected at regular time intervals, via chronic indwelling jugular cannulae, before and after drug administration and plasma prolactin was determined by radioimmunoassay. TIDA neuronal activity was measured using the 3,4‐dihydroxyphenylacetic acid (DOPAC) : dopamine ratio in the median eminence 2 h 30 min after i.c.v. drug injection. In each experimental condition, plasma prolactin was significantly inhibited by both κ‐ and μ‐receptor antagonists, whereas the δ‐receptor antagonist had no effect compared to saline‐injected controls. Similarly, nor‐binaltorphimine and beta funaltrexamine significantly increased the median eminence DOPAC : dopamine ratio during early and late pregnancy, and lactation whereas naltrindole had no effect compared to saline‐injected controls. These data suggest that TIDA neuronal activity, and subsequent prolactin secretion, is regulated by endogenous opioid peptides acting at both κ‐ and μ‐opioid receptors during prolactin surges of early pregnancy, late pregnancy and lactation.
A comparison between the wear resistance of three typesof denture resin to three different dentifrices
Authors: Haselden  , Hobkirk  , Pearson  , Davies
Published: March 2003

This study compares the abrasive effects of three dentifrices on three different denture base resins, a heat cured acrylic resin, a self cured acrylic resin and a light activated urethane dimethacrylate‐based resin. Specimens of the resins were subjected to a regimen of mechanical brushing using measured amounts of paste on standard toothbrushes driven by a reciprocating device. The apparent wear of each specimen was assessed qualitatively using scanning electron microscopy and quantitatively using profilometry and reflex microscopy. The study showed that cleaning pastes play a significant role in the wear of conventional acrylic resins, the relative abrasivity of the dentifrices being substrate related. However, wear was less evident on the light activated urethane dimethacrylate resin. Brushing with water alone produced no detectable wear on any of the specimens.
Denture mobility with six degrees of freedom during function
Authors: Miyashita K. , Sekita T. , Minakuchi S. , Hirano Y. , Kobayashi K. , Nagao M.
Published: March 2003

SUMMARY The purpose of this study was (1) to assemble and verify a system to measure the three‐dimensional (3‐D) movement of the upper and lower complete dentures and the movement of the mandible simultaneously, and (2) to analyse the relation between denture movements and the path of closure of the mandible during function. A 3‐D motion capture system with four infrared TV cameras was used for this purpose. The relation between the dentures and the mandibular movements was analysed through the change of the inner product of normal vectors of the denture occlusal planes and mandibular planes. The mandibular movements were classified into two types the normal stroke (the path of closure was on the ipsilateral side of mastication) and the reverse stroke (on the contralateral side). The results showed that the system could measure the denture mobility within a 0·3 mm error. The mobility of the upper dentures had a correlation to the path of closure of the mandible regardless of the working side or nonworking side, and the lower dentures had a tendency to move toward the working side.
Relationship between juvenile bruxing and craniomandibular dysfunction
Authors: Kieser J. A. , Groeneveld H. T.
Published: March 2003

A longitudinal study was conducted over 5 years to investigate the relationship between juvenile bruxing and craniomandibular disorders. A total of 150 bruxers between the ages of 6 and 9 years were examined for oral parafunctions and TMJ symptoms. Of these, 126 were re‐examined for the same signs and symptoms after 5 years. The results showed that only 17 individuals had retained their bruxing habit. In common with other studies, we found that symptoms reduced with age. It was concluded that juvenile bruxing was a self‐limiting condition which does not progress to adult bruxism and which appeared to be unrelated to TMJ symptoms.
The relationship between satisfaction with mouth and number and position of teeth
Authors: Elias A. C. , Sheiham A.
Published: March 2003

A number of studies have suggested that many people are satisfied with less than 28 natural teeth. This review assesses the evidence. The main conclusion was that less than a complete dentition can satisfy oral functional needs. Missing posterior teeth were not very important from a subjective aspect. The demand for replacement of missing teeth is related to the position of missing teeth. Most studies agree that individuals were more concerned about missing anterior teeth and having anterior rather than posterior teeth replaced. Aesthetics is more important than function for a great majority of individuals. However, certain socio‐demographic factors, such as age, can change the subjective need for replacement of missing teeth. Some studies have assessed the social and psychological impacts on oral health status. The position of missing teeth was assessed, in terms of groups of missing teeth, anterior or posterior, that would affect an individuals’ subjective need for replacement by partial prosthesis. Large numbers of people that have free end removable partial dentures made do not wear them because subjective needs are lower than normatively determined needs for replacement of missing teeth. Some studies have proposed alternatives to the replacement of missing teeth, such as the shortened dental arch concept.
In vitro cytotoxicity of fibre–polymethyl methacrylate composite used in dentures
Authors: Vallittu P. K. , Ekstrand K.
Published: March 2003

The aim of this study was to determine the in vitro cytotoxicity of fibre–polymethyl methacrylate (PMMA) composite used in denture bases. Both heat‐cured and autopolymerized PMMA were tested as the matrix of the fibre composite or as a plain denture polymer. The fibres tested included unsized E‐glass and silica fibres, silica fibres which were sized with a silane coupling agent only, as well as commercially epoxy–silane or methacrylate–chrome complex sized E‐glass fibres. The indirect contact cytotoxicity test by agar diffusion was carried out according to the international standard ISO 10993‐5 after storing the test specimens in water for 24 h. PVC plastic was used as a positive control and polyethylene plastic was used as a negative control. Within the limitations of the agar diffusion test, it can be concluded that neither the unreinforced PMMA nor the fibre composite made from PMMA and fibres was cytotoxic.
The effectiveness of a new algorithm on a three‐dimensional finite element model construction of bone trabeculae in implant biomechanics
Authors: Sato Y. , Teixeira E. R. , Tsuga K. , Shindoi N.
Published: March 2003

More validity of finite element analysis (FEA) in implant biomechanics requires element downsizing. However, excess downsizing needs computer memory and calculation time. To evaluate the effectiveness of a new algorithm established for more valid FEA model construction without downsizing, three‐dimensional FEA bone trabeculae models with different element sizes (300, 150 and 75 μm) were constructed. Four algorithms of stepwise (1 to 4 ranks) assignment of Young's modulus accorded with bone volume in the individual cubic element was used and then stress distribution against vertical loading was analysed. The model with 300 μm element size, with 4 ranks of Young's moduli accorded with bone volume in each element presented similar stress distribution to the model with the 75 μm element size. These results show that the new algorithm was effective, and the use of the 300 μm element for bone trabeculae representation was proposed, without critical changes in stress values and for possible savings on computer memory and calculation time in the laboratory.
Depth of cure of prosthetic composite materials polymerized with laboratory and handheld photo‐curing units
Authors: Matsumura H. , Tanoue N. , Atsuta M.
Published: March 2003

This study examined depth of cure of two prosthetic composite materials (Artglass® and Dentacolor®) polymerized by means of four photo‐curing units for the purpose of comparing the curing performance of laboratory and handheld curing units. Each composite material was photo‐exposed either with one of two laboratory photo‐curing units (Dentacolor XS® and UniXS®) or with one of two handheld photo‐curing units (Translux CL® and Translux EC®). The light sources were differently shaped xenon stroboscopic lamps for the laboratory units, and halogen lamps of differing intensity for the handheld units. Exposure periods were 20, 30, 60, and 90 s, and depth of cure of the materials was determined with a scraping technique. The two handheld curing units generated significantly greater depth of cure for both materials than either of the two laboratory curing units. Of the two laboratory units, the Dentacolor XS® unit produced somewhat greater depth of cure for all combinations than the UniXS® unit, whereas the differences in depth of cure of the two materials exposed with the two handheld units were not significant when the exposure time period was 60 s or more. The Dentacolor® composite generally demonstrated greater depth of cure than the Artglass® composite under identical curing conditions.
Investigation of a possible relationship between kinematic points and condylar attachments of the lateral ligaments
Authors: Pröschel P. A. , Morneburg T.
Published: March 2003

Kinematic points are proposed as reference for assessment of condyle motion. They are defined by coincidence between open–closing and protrusive trajectories. According to anatomical findings, this feature should also apply to the condylar attachment of the lateral ligament that should guide the condyle on an arc around its tubercular fixation. Our aim was to examine if evidence for a correspondence between the kinematic point and the condylar attachment of the ligament could be derived from condylar dynamics. In 60 asymptomatic volunteers, open–closing and protrusive jaw movements were recorded with 6 d.f. Kinematic points were found 2·5±2·9 mm anterior and 4·3±2·9 mm inferior from the terminal‐hinge point. Their coinciding traces could be fitted by arcs with radii of 11·7±2·2 mm. The centres of the arcs were found 10·4±1·6 mm anterior and 4·9±2·4 mm superior from the kinematic points. When compared to anatomy, the local distributions of kinematic points and arc centres corresponded well to the condylar and tubercular fixation areas of the ligament. The findings provide circumstantial evidence for a correspondence between kinematic points and the attachment of the lateral ligament. Kinematic points could provide a better means to assess condyle motion than other posterior landmarks, when in addition, movements of adjacent points and rotational properties are considered.
Streptococcus mutans in saliva of normal subjects and neck and head irradiated cancer subjects after consumption of honey
Authors: Sela MO. , Maroz D. , Gedalia I.
Published: March 2003

The antibacterial activity of natural honey consumption has been examined in patients suffering from head and neck cancer who developed hyposalivation following irradiation treatment. Enumeration of total bacteria and streptococcus mutans was carried out in saliva of the patients and of a normal volunteer group before and after honey consumption. Total bacteria count was not significantly different between both groups, whereas the streptococcus mutans count decreased significantly in the experimental group following honey consumption.
The involvement of the styloid process in head and neck pain—a preliminary study
Authors: Palesy P. , Murray G. M. , De Boever J. , Klineberg I.
Published: March 2003

The styloid process and associated structures have been implicated in a variety of craniomandibular dysfunctions and pain complaints. There have been anecdotal reports that treatment directed at this area can result in a dramatic reduction in referred symptoms, somatic pain and autonomic signs as well as an increase in mandibular range of motion. In the past, an elongation of the styloid process was considered necessary for pain and dysfunction symptoms to arise from this area. The patients in this study did not have elongated styloid processes, yet had orofacial pain and dysfunction symptoms seemingly referred from this area. An injection of local anaesthetic and corticosteroid in the area of the styloid process significantly reduced lateral head pain and improved mandibular function in spite of an absence of any demonstrable pathology at the styloid process.
Stress distribution associated with loaded ceramic onlay restorations with different designs of marginal preparation. An FEA study
Authors: Abu‐Hassan M. I. , Abu‐Hammad O. A. , Harrison A.
Published: March 2003

The design of marginal finish of an inlay or onlay could influence the prognosis of the restoration since this area is subjected to various mechanical or chemical actions during function. This study was carried out to determine the tensile stresses which develop at the marginal area when subjected to vertical and horizontal loads. Onlay restorations with three different types of marginal finish, i.e. shoulder, chamfer and bevel, were modelled in three dimensions using the finite element method, and were then subjected to vertical and horizontal load at three different sites. The results show that horizontal forces acting on the restoration generate the highest tensile stresses whilst the vertical forces generate high tensile stresses at the margins of the chamfer and bevel designs.
Comparison of in vitro fracture strength of metallic and tooth‐coloured posts and cores
Authors: Rosentritt M. , Fürer C. , Behr M. , Lang R. , Handel G.
Published: March 2003

In root‐treated anterior teeth a better aesthetic can be achieved by using translucent and tooth‐coloured post and core restorations instead of traditional metal post systems. The aim of this in vitro study was to compare the fracture strength of tooth‐coloured ceramic and fibre‐reinforced posts as well as titanium posts with clinically proven gold alloy posts as a control. Two all‐ceramic, one gold alloy and three combined post restoration systems (titanium and ceramic, respectively, fibre‐reinforced posts with composite core) were each applied to upper incisors and after thermal cycling and mechanical loading (TCML) the fracture strength was determined. The variant providing the most reliable fracture strength values and the experimental fibre‐reinforced composite (FRC) posts were – in combination with adhesively luted crowns – used to determine the fracture strength of the restoration after thermal cycling and mechanical loading. The median fracture strength of the luted posts and cores fluctuated between 114 and 546 N. Posts with composite cores demonstrate a higher fracture strength in comparison to the all‐ceramic and gold alloy systems. Typical failure of metal systems was marked by loosening of the bonding and pulling out of the post in contrast to fracture of the ceramic posts. After the application of the crowns the ceramic system with composite core provided a fracture strength of 338 N and the FRC system a fracture strength of 228 N. Regarding fracture strength, the ceramic posts with composite cores are an alternative to commonly used gold posts and cores. A standardized technical manufacture of FRC posts and cores would provide better fracture strength results of this new dental material. Post and core restorations with tooth‐coloured, translucent material offer an improved aesthetic especially in anterior restorations. Because of the high fracture strength prefabricated ceramic posts in combination with composite cores should prove their clinical applicability.
Cephalometric estimation of Vertical Dimension of Occlusion
Authors: Orthlieb J.‐D. , Laurent M. , Laplanche O.
Published: March 2003

The literature does not establish a single proven method for determining lower facial height, which is called the Vertical Dimension of Occlusion (VDO), and the concept of a vertical comfort range is generally accepted. This study aimed to test the statistical significance of correlations of mandibular shape versus lower facial height in occlusion, using cephalometric measurements. Correlations for 505 consecutive healthy adults were calculated between angles that estimate the lower facial height and angles that estimate the mandibular shape. The mandibular angle (gonial) showed a higher coefficient of correlation (r=0·691) than the inferior gonial angle. The dispersion remained large, i.e. r2=0·478. Cephalometric measurements, despite theirs imperfections, could help the practitioner to understand what the best course of treatment would be in order to obtain a lower facial height in occlusion showing a skeletal harmony with the mandibular shape.
A study on the mandibular movement of anterior openbite patients
Authors: Koak J.‐Y. , Kim K.‐N. , Heo S.‐J.
Published: March 2003

The purpose of this study was to compare the mandibular movements of anterior openbite patients using those of normal bite (angle class I) patients, to ascertain which components of mandibular movement are different in the two groups, and to use this information for occlusal treatment. The Saphon Visi‐trainer Model 3 and the Denar Pantronic were used to record mandibular movement and a Pantronic survey was performed using an arbitrary hinge axis, according to manufacturer's instructions. The subjects were 43 adults and included 28 subjects presenting with acceptable normal occlusion (angle class I) with no sign of TM dysfunction syndrome (TMD) and 15 subjects with anterior openbite with no anterior guidance. In the anterior openbite group, the average anterior and lateral condylar inclination, maximum opening and the distance between the intercuspal position with retruded contact position distance (anterior–posterior) were significantly lower than normal. The results suggest that in openbite patients the condyle inclination is flatter and the function of the TMJ is more restricted than in the mandibular movements of the normal group. It is hoped that these results will be useful for the correction of the anterior openbite condition.
Fluoride release from glass–ionomer cements, compomers and resin composites
Authors: Vermeersch G. , Leloup G. , Vreven J.
Published: March 2003

The short and long‐term fluoride release of 16 products (seven conventional glass–ionomers, five light‐activated glass–ionomers, two polyacid‐modified resin composites and two resin composites) commercialized as fluoride‐releasing materials were measured. A potential link between the material type and its level of fluoride release was researched. The fluoride release was evaluated after different time intervals. Initial fluoride release from all materials was highest during the first 24 h and decreased sharply over the first week. Some groups of materials appeared to be significantly different after, respectively, 7 and 91 days. However, it was impossible to correlate the fluoride release of the materials by their type (conventional or resin‐modified glass–ionomers, polyacid‐modified resin composite and resin composite) except if we compared the products from the same manufacturer. The link between fluoride release and an acid–base reaction seems to be confirmed. The glass–ionomer composition (glass particles and polyacid's type, powder/liquid ratio) should have more influence on fluoride release than material type.
Finite element analysis on preferable I‐bar clasp shape
Authors: Sato Y. , Tsuga K. , Abe Y. , Asahara S. , Akagawa Y.
Published: March 2003

An I‐bar clasp is one of the most popular direct retainers for distal‐extension removable partial dentures. However, no adequate information is available on preferable shape as determined by biomechanics. This study aimed (1) to investigate, by finite element analysis (FEA), the dimensions and stress of I‐bar clasps having the same stiffness, and (2) to estimate a mechanically preferable clasp design. Three‐dimensional FEA models of I‐bar clasps were created with vertical and horizontal straight sections connected by a curved section characterized by six parameters: thickness of the clasp tip, width of the clasp tip, radius of the curvature, horizontal distance between the base and the vertical axis, vertical dimension between the tip and the horizontal axis, and taper (change of width per unit length along the axis). Stress was calculated with a concentrated load of 5 N applied 2 mm from the tip of the clasp in the buccal direction. A thinner and wider clasp having an taper of 0·020–0·023 and radius of curvature of 2·75–3·00 showed less stress. The results suggest that such a shape might be the preferable I‐bar clasp shape as biomechanical viewpoint.
Pain measurement in TMD patients: evaluation of precision and sensitivity of different scales
Authors: Conti Paulo César Rodrigues , De Azevedo Luciana Reis , De Souza Natália Viana Waltric , Ferreira Fábio Venturini
Published: March 2003

The aim of this study was to evaluate the precision and sensitivity of four different pain rating scales in 59 temporomandibular disorders (TMD) patients. The capacity of describing changes in symptoms during treatment was also addressed. All patients were asked to answer four pain scales: Visual Analogue Scale (VAS), Numerical Scale (NS), Behaviour Rating Scale (BRS) and Verbal Scale (VS). Two measurements were taken before any treatment. After beginning it, follow‐ups and repeated measurements were taken 1 week, 15 days, and every month for 6 months. Statistical analysis showed significant differences (P < 0·05) for all scales, but the NS (P > 0·05), when the two initial measurements were analysed. Regarding the sensitivity, all pain scales demonstrated general symptom improvement of 30–50%, when initial and final figures were compared (P < 0·01). Also, the most significant improvement occurred in the first 2 months after beginning the management programme. Authors concluded that the NS was more accurate to measure reproducibility of pain. As for the capacity of expressing changes during the treatment, all scales demonstrated symptom decrease of 30–50% in a period of 6 months. Caution when analysing the results is recommended because of the subjective aspect of pain measurement, the absence of a ‘gold standard’ for comparison and the natural fluctuation of TMD symptoms.
Anatomical study of the pyramidal process of the palatine bone in relation to implant placement in the posterior maxilla
Authors: Lee S. P. , Paik K. S. , Kim M. K.
Published: March 2003

The placement of dental implants in the molar region of the maxilla is often difficult because of insufficient bone volume and the inferior bone quality. In order to avoid these limitations, the pillar of bone, which is composed of the maxillary tuberosity, the pyramidal process of the palatine bone and the pterygoid process of the sphenoid bone, was introduced for implant placement. In fact, the pyramidal process is the posterior structure where implants are placed but until now, there is no available data of the size or shape of the pyramidal process. Therefore, we measured the height, anteroposterior distance and mediolateral distance of the pyramidal process and observed the shape of lateral and posterior surfaces of the pyramidal process of 54 Korean edentulous dry skulls in this study. The height was 13·1 mm (male: 13·6 mm, female: 12·4 mm). The anteroposterior distance was 6·5 mm (male: 6·7 mm, female: 6·1 mm). The mediolateral distance was 9·5 mm (male: 9·9 mm, female: 9·0 mm). The most common type was the right‐angled triangle in the lateral surface (44·4%) and in the posterior surface (66·7%). There was no statistical significance between the male and the female in all items (P > 0·05). These results provide anatomical features in relation to placement of dental implants in the molar region of the maxilla and would be useful in treatment planning of partially or completely edentulous patients.
Effectiveness of exercise therapy in patients with internal derangement of the temporomandibular joint
Authors: Nicolakis P. , Erdogmus B. , Kopf A. , Ebenbichler G. , Kollmitzer J. , Piehslinger E. , Fialka‐Moser V.
Published: March 2003

This study intended in evaluating the effectiveness of exercise therapy in patients with craniomandibular disorders (CMD). Twenty consecutive patients suffering from CMD with anterior disc displacement without reduction consulting a CMD service were included in the study if they met following criteria: (i) pain in the temporomandibular region, (ii) reduced incisal edge clearance (<35 mm), (iii) magnet resonance imaging confirmed anterior disc displacement without reduction and (iv) evidence of postural dysfunction. All patients were assigned to a waiting list, serving as a no‐treatment control period, according to a before–after trial. The treatment consisted of active and passive jaw movement exercises, correction of body posture and relaxation techniques. A total of 18 patients completed the study, no adverse effects occurred. Following main outcome measures were evaluated: (1) pain at rest (2) pain at stress (3) impairment (4) mouth opening at base‐line, before and after treatment and at 6 month follow‐up. As a result of treatment pain, impairment and mouth opening improved significantly more than during control period (paired samples t‐test P < 0·05). After treatment four patients had no pain at all (chi‐square: P < 0·05) and only seven patients revealed an impaired incisal edge clearance after treatment. (chi‐square Test, P < 0·001). At follow up, seven patients had no pain and experienced no impairment. Exercise therapy seems to be useful in the treatment of anterior disc displacement without reduction.
Water sorption and solubility of dental composites and identification of monomers released in an aqueous environment
Authors: Örtengren U. , Wellendorf H. , Karlsson S. , Ruyter I. E.
Published: March 2003

Water sorption and solubility of six proprietary composite resin materials were assessed, and monomers eluted from the organic matrix during water storage identified. Water sorption and solubility tests were carried out with the following storage times: 4 h, 24 h and 7, 60 and 180 days. After storage, water sorption and solubility were determined. Eluted monomers were analysed by high performance liquid chromatography (HPLC). Correlation between the retention time of the registered peak and the reference peak was observed, and UV‐spectra confirmed the identity. The results showed an increase in water sorption until equilibrium for all materials with one exception. The solubility behaviour of the composite resin materials tested revealed variations, with both mass decrease and increase. The resin composition influences the water sorption and solubility behaviour of composite resin materials. The HPLC analysis of eluted components revealed that triethyleneglycol dimethacrylate (TEGDMA) was the main monomer released. Maximal monomer concentration in the eluate was observed after 7 days. During the test period, quantifiable quantities of urethanedimethacrylate (UEDMA) monomer were observed, whereas 2,2‐bis[4‐(2‐hydroxy‐3‐methacryloyloxypropoxy)‐phenyl]propane (Bis‐GMA) was only found in detectable quantities. No detectable quantities of bisphenol‐A were observed during the test period.
Shear bond strengths of saliva contaminated `one‐bottle' adhesives
Authors: Taskonak B. , Sertgöz A.
Published: March 2003

The aim of this study was to investigate the effect of saliva contamination on the bond strengths of three one‐bottle bonding systems. The dentin of 90 recently extracted, non‐carious human molar teeth was exposed and ground wet on 500 grit silicon carbide (SIC) paper to establish a bonding surface in superficial dentin. Specimens were randomly assigned to nine groups of 10 teeth each. Three testing conditions are: (i) contamination with fresh saliva (pH 5·5) after acid etching, (ii) contamination with fresh saliva after bonding application, and (iii) no contamination. Three adhesive systems are: syntac single component, prime & bond NT, and gluma one bond. Cylinders of composite were applied via PTFE (polytetrafluroethylene) split mould and light cured to the dentin surfaces. All specimens were thermocycled (5000 cycles) between baths of 5 and 55 °C. Shear bond strengths were measured using an Instron Universal testing machine at a crosshead speed of 1 mm min–1. Two‐way ANOVA was used to analyse the data. The results of this study indicated that the saliva contamination of dentin has no adverse effect on the bonding efficiency of one‐bottle adhesive systems (P > 0·05). No statistically significant differences were found between the shear bond strengths of tested adhesives.