bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Steroid‐Induced Genes in the Rat Preoptic Area‐Anterior Hypothalamus Using a Differential‐Display Reverse Transcriptase‐Polymerase Chain Reaction
Authors: Park S. , Seong J. Y. , Son G. H. , Kang S. S. , Lee S. , Kim S. R. , Kim K.
Published: March 2003

Steroid hormones modulate a variety of physiological functions in the hypothalamus. We attempted to identify steroid‐regulated genes in the rat preoptic area‐anterior hypothalamus by comparing differentially expressed mRNAs. Adult female rats were ovariectomized and, 1 week later, a silastic capsule containing 17β‐oestradiol (180 µg/ml) was subcutaneously implanted. After 2 days, a single injection of progesterone (1 mg) was administered at 10.00 h and rats were killed at 17.00 h on the same day. Differential‐display polymerase chain reaction followed by Northern blot analysis showed that 10 clones were differentially regulated. Using homology search in Genbank, three genes were identified as sodium, potassium‐ATPase β1, protein kinase C‐binding Nell‐homologue protein and evectin‐1. Further characterization of 10 clones showed that the expression patterns were tissue‐specific and differentially regulated during puberty. Among these, mRNAs for protein kinase C‐binding Nell‐homologue protein, evectin‐1 and human CGI‐118 protein‐like gene were induced after vagina opening, and differentially expressed during the oestrous cycle. Taken together, several steroid‐regulated genes identified in the present study may play an important role in regulating hypothalamic functions, including puberty and the oestrous cycle.
Role of Extra‐Ovarian Oestrogens in the Regulation of Gonadotropin Releasing Hormone mRNA Expression in the Rat Brain
Authors: Pelletier G. , Labrie C. , Martel C. , Li S. , Labrie F.
Published: March 2003

To further understand the role of oestrogens in the regulation of gonadotropin releasing hormone (GnRH) mRNA expression in the female rat brain, the effect of EM‐652.HCl, a pure anti‐oestrogen, was studied in intact and ovariectomized rats as well as in rats chronically treated with a GnRH agonist d‐trp6, des‐Gly‐NH210 GnRH ethylamide (GnRH‐A), a treatment which blocks ovarian steroidogenesis. Quantitative in situ hybridization was used to measure GnRH mRNA at the cellular level in the preoptic‐anterior hypothalamic area. It was found that, 49 weeks after ovariectomy (OVX), the number of silver grains per cell corresponding to GnRH mRNA was increased by 34%. Long‐term administration (49 weeks) of EM‐652.HCl to OVX rats resulted in a further increase (11% over the levels measured in OVX rats) in the hybridization signal. By contrast, in intact female rats, treated during 52 weeks with EM‐652.HCl, a 49% increase in the GnRH hybridization signal was detected. In rats treated with GnRH‐A during the same period, a 20% decrease in GnRH mRNA was observed. When EM‐652.HCl was administered concomitantly with GnRH‐A, a further 63% increase over the mRNA levels recorded in GnRH‐A treated rats was found. Thus, long‐term treatment with the anti‐oestrogen EM‐652.HCl can upregulate GnRH mRNA expression in intact female rats, OVX rats and female rats chronically treated with a GnRH‐A. It is suggested that the pure anti‐oestrogen EM‐652.HCl can exert an influence on the oestrogen feedback mechanism involved in the regulation of GnRH neuronal activity by neutralizing the action of locally produced or low circulating levels of oestrogens remaining after OVX or GnRH‐A treatment.
Facilitation of Ca2+ Store‐Dependent Noradrenaline Release After an N‐Methyl‐d‐Aspartate Receptor Antagonist in the Rat Supraoptic Nucleus
Authors: Liu X. , Onaka T. , Yagi K.
Published: March 2003

We examined the role of N‐methyl‐d‐aspartate (NMDA) receptors in the control of noradrenaline release in the supraoptic nucleus (SON) using a microdialysis method in urethane‐anaesthetized rats. Local application of 0.5 mm NMDA into the SON by retrodialysis decreased noradrenaline content in the dialysate from the SON. On the other hand, MK‐801, a channel blocker of NMDA receptors, or D(–)2‐amino‐5‐phosphonopentanoic acid (AP‐5), a competitive NMDA receptor antagonist, increased the basal noradrenaline content. Tetrodotoxin did not completely block the noradrenaline increase after NMDA antagonists. Infusion of Ca2+‐free solution containing Ni2+ and Cd2+, or a mixture of ω‐agatoxin IVA and ω‐conotoxin GVIA, voltage‐sensitive Ca2+ channels blockers, did not block noradrenaline increase after AP‐5, but blocked noradrenaline increase after high K+. Infusion of intracellular Ca2+ blockers, thapsigargin or TMB‐8, impaired noradrenaline increase after AP‐5 but not that after high K+. These data are consistent with the hypothesis that activation of an NMDA receptor inhibits an intracellular Ca2+ store‐dependent noradrenaline release from nerve terminals in the SON.
Differential Expression of Vasopressin, Oxytocin and Corticotrophin‐Releasing Hormone Messenger RNA in the Paraventricular Nucleus of the Prairie Vole Brain Following Stress
Authors: Liu Y. , Curtis J. T. , Fowler C. D. , Spencer C. , Houpt T. , Wang Z. X.
Published: March 2003

Forced swimming, as an effective stressor, has been found to facilitate the development of pair bonds in male but to interfere with this behaviour in female prairie voles (Microtus ochrogaster). In the present study, we found that forced swimming differentially influenced the expression of messenger RNA for vasopressin, oxytocin and corticotrophin‐releasing hormone (CRH) in the paraventricular nucleus of the hypothalamus (PVN) in the prairie vole brain. Forced swimming did not alter vasopressin mRNA labelling, but did induce a sustained decrease in oxytocin mRNA labelling and a progressive increase in CRH mRNA labelling in the PVN. The elevated CRH mRNA labelling appeared to be due to an increased number of cells synthesizing CRH mRNA and an enhanced ability of individual cells to produce CRH mRNA. Male and female prairie voles did not differ in the vasopressin, oxytocin or CRH mRNA expression either at the basal levels or in response to swimming stress. Together, these data indicate that the hypothalamic response of vasopressin, oxytocin and CRH messenger RNAs to swimming stress is regulated by distinct transcriptional factors. In addition, it seems unlikely that these changes are involved directly in the sex differences in pair bond formation.
Ventral Tegmental Area Infusions of Inhibitors of the Biosynthesis and Metabolism of 3α,5α‐THP Attenuate Lordosis of Hormone‐Primed and Behavioural Oestrous Rats and Hamsters
Authors: Frye C. A. , Vongher J. M.
Published: March 2003

The importance of progesterone biosynthesis and metabolism to 5α‐pregnan‐3α‐ol‐20‐one (3α,5α‐THP), which exerts its effects via GABAA/benzodiazepine receptor complexes (GBRs) rather than intracellular progestin receptors (PRs), was investigated for its effects on sexual receptivity. Epostane, a 3β‐hydroxysteroid dehydrogenase inhibitor, blocks progesterone and 3α,5α‐THP biosynthesis. Finasteride, a 5α‐reductase inhibitor, blocks the metabolism of progesterone to dihydroprogesterone (DHP), which is subsequently metabolized to 3α,5α‐THP. Indomethacin, a 3α‐hydroxysteroid oxidoreductase inhibitor, blocks DHP's metabolism to 3α,5α‐THP, and its oxidation to DHP. Epostane, finasteride, indomethacin or vehicle were infused intracranially in the ventral tegmental area (VTA) of hormone‐primed or naturally receptive rats and hamsters and sexual behaviour was recorded. Epostane, finasteride and indomethacin to the VTA significantly reduced lordosis, compared to vehicle infusions, in hormone‐primed and behavioural oestrous rats and hamsters. Radioimmunoassay revealed that concentrations of midbrain 3α,5α‐THP were reduced following epostane, finasteride or indomethacin infusions that significantly decreased lordosis. Immunocytochemistry for 3α,5α‐THP revealed the number of immunoreactive cells were significantly reduced in the VTA following epostane, finasteride or indomethacin infusion to the VTA, but not other midbrain sites. These data suggest that biosynthesis of progestins, and the metabolism of progesterone to 3α,5α‐THP in the VTA, are important for progestin‐facilitated sexual receptivity of rats and hamsters.
Coregulator Proteins and Corticosteroid Action in the Brain
Authors: Meijer O. C.
Published: March 2003

The corticosteroid hormones cortisol and corticosterone are secreted by the adrenal gland in response to stress. They have profound effects on brain function, which are mediated by the related mineralocorticoid (MR) and glucocorticoid (GR) receptors. The MR and GR are ligand‐activated transcription factors and exert different, sometimes opposing effects on the brain. The balance between these two receptor activities is considered essential for appropriate corticosteroid signalling and health. An exciting recent insight in steroid biology is that the nature and magnitude of steroid receptor‐mediated responses depend not only on ligand and receptor availability, but also in a critical manner on the presence of downstream mediator proteins (coregulators), such as the steroid receptor coactivators and nuclear receptor corepressors. Members of the coregulator families differ in their specific interactions with steroid receptors, as well as in their distribution throughout the brain and pituitary. The activity of these proteins can be regulated both at the expression level, and by post‐translational modifications. These characteristics make coregulator proteins of outstanding interest as determinants of receptor, cell and state‐dependent effects of MR and GR signalling (and steroid receptor signalling in general) in the brain.
Genetic Selection For Coping Style Predicts Stressor Susceptibility
Authors: Veenema A. H. , Meijer O. C. , De Kloet E. R. , Koolhaas J. M.
Published: March 2003

Genetically selected aggressive (SAL) and nonaggressive (LAL) male wild house‐mice which show distinctly different coping styles, also display a differential regulation of the hypothalamic‐pituitary‐adrenal axis after exposure to an acute stressor. To test the hypothesis that coping style predicts stressor susceptibility, the present study examined line differences in response to a chronic stressor. Chronic psychosocial stress was evoked using two paradigms. In the first paradigm, a SAL or LAL male was living in sensory contact (except tactile contact) with a dominant SAL male for 25 days (sensory contact stress). In the second paradigm, a SAL or LAL male was, in addition to the first paradigm, defeated by a SAL male for 21 consecutive days (defeat stress). The sensory contact stressor induced in LAL mice chronic body weight loss and increased plasma adrenocorticotropic hormone levels compared to SAL mice and increased corticosterone levels, thymus involution and lower hippocampal mineralocorticoid receptor (MR) : glucocorticoid receptor (GR) ratio compared to LAL controls. The defeat stressor increased corticosterone secretion and caused adrenal hypertrophy and thymus involution in both mouse lines. Defeated LAL mice showed long‐lasting body weight loss and higher corticosterone concentrations than SAL mice and lower hippocampal MR : GR ratio and decreased immobility behaviour in the forced swimming test than LAL controls. Hypothalamic corticotropin‐releasing hormone mRNA expression was higher in defeated SAL than in controls. The present data show that both stress paradigms induced line‐dependent physiological and neuroendocrine changes, but that the sensory contact stressor produced chronic stress symptoms in LAL mice only. This latter stress paradigm therefore seems promising to analyse the role of genetic factors in the individual differences in stress‐related psychopathology.
Effects of stabilization appliances on nocturnal parafunctional activities in patients with and without signs of temporomandibular disorders
Authors: Yap
Published: March 2003

This study was designed to investigate the short‐term effects of stabilization appliances on parafunctional oral motor behaviour (bruxing and clenching) during sleep in patients with and without signs of temporomandibular disorders (TMD). Results revealed that stabilization appliances do not stop nocturnal parafunctional activities in both groups of patients. Active wear facets on the guide ramps of appliances were created by bilateral mandibular excursions. The extension of these facets indicate that the mandible moves laterally far beyond the edge‐to‐edge contact relationship of the canines during eccentric bruxism. Results also indicate that, with the exception of temporomandibular joint (TMJ) clicks, stabilization appliance therapy is effective in eliminating the signs of TMD evaluated.
The adverse effect of commercial dentine‐bonding systems on the skin of guinea pigs
Authors: Katsuno  , Manabe  , Kurihara  , Itoh  , Hisamitsu  , Wakumoto  , Yoshida
Published: March 2003

It was widely known that 2‐hydroxyethyl methacrylate (2‐HEMA) can cause contact dermatitis. Commercially available dentine primers and dentine bonding agents that contain 2‐HEMA are widely used. The purpose of this study was to investigate the cumulative irritation and delayed hypersensitivity caused by commercial dentine bonding systems when applied to the skin of guinea pigs. We have concluded that almost no dentine bonding systems cause cumulative irritation, but some commercially available dentine bonding systems may produce delayed hypersensitivity.
The effect of sprue design on the marginal accuracy of titanium castings
Authors: Chan  , Blackman  , Kaiser  , Chung
Published: March 2003

The purpose of this study was to measure the effects of sprue number and position on cast titanium crown margins. Twenty‐four complete veneer crown wax patterns were fabricated on a stainless steel die with a 30° bevel finish line. Twelve wax patterns were sprued with one 8‐gauge wax sprue and the remaining 12‐gauge double sprued. All patterns were invested with a phosphate bonded investment. Castings were made with a titanium casting machine following the manufacturer’s instructions and using commercially pure titanium (> 99·5%) ingots. The castings were than carefully cleansed and the margins were examined with indirect impression technique. Data were analysed with an ANOVA and the Student’s t‐test with confidence level at 95%. The results revealed that the marginal discrepancy for the double sprueing group (32·1 ± 12·8 μm) has significantly less discrepancy (P < 0·001) than the single sprueing group (49·8 ± 16·4 μm). There was no statistically significant differences in marginal discrepancy between locations within the sprueing techniques (P > 0·05). An improvement in the degree of casting accuracy of titanium crown was indicated by the double sprue design used in this investigation.
Changes on storage of polyacid‐modified composite resins
Authors: Nicholson  , Alsarheed
Published: March 2003

summary Two polyacid‐modified composite resins, Dyract® and Compoglass®, have been studied for water‐uptake on storage in three aqueous media, namely pure water, 0·9% NaCl and 1 M NaCl at 37°C, and the results compared with those of a conventional composite resin, Pekafill®. The equilibrium water‐uptake of Dyract® and Compoglass® varied depending on time of cure and ionic strength of the storage medium. This latter finding contrasted with that for Pekafill®, where equilibrium water content showed almost no variation with ionic strength of the storage medium. Uptake of water was always greater in Dyract® and Compoglass® than in Pekafill®, reflecting the role of water in promoting the later neutralization reaction in these materials and its further role in hydrating the ionic products of that reaction. Despite this and other evidence of neutralization, specimens of Dyract® and Compoglass® stored in wet conditions (0·9% NaCl) showed no change in compressive strength on storage from 24 h to 30 days, a result similar to that reported previously for Dyract® alone for flexural strength for times up to 1 year. By contrast, specimens of Dyract® and Compoglass® stored in dry air at 37°C, and therefore unable to undergo any neutralization, showed an increase in compressive strength of between 40 and 70 MPa by 30 days that was significant at P < 0·01.
Effect of primers on bonding agent polymerization
Authors: Hotta M. , Kondoh K. , Kamemizu H.
Published: March 2003

The aim of the present study was to evaluate the effect of primers on the polymerization of bonding agent. We measured the degree of conversion (radical production) and mechanical properties (surface hardness and direct tensile strength) of various adhesives/primers mixed at different ratios and the effect of varying the visible‐light curing time. With and without primer treatment, the tensile bond strength of adhesive resin to micacious glass ceramic and human enamel was measured. After the tensile bond test, using the Image Capture System, the failure patterns of adhesive resin bonded to micacious glass‐ceramic were analysed. The results show that the mixtures containing the higher amounts of primer yielded a lower degree of conversion and inferior mechanical properties when compared with the mixtures containing a lower proportion of primer, except in the experimental bonding system. The adhesive/primer mixtures inhibited free radical polymerization. The value for the Knoop hardness number and the direct tensile strength of the adhesive/primer mixtures were significantly decreased compared with those of the adhesive bonding agent alone with no primer added. The tensile bond strength of adhesive resin bonded to micacious glass‐ceramic or human enamel without primer treatment was significantly greater than that of adhesive resin with primer treatment in certain cases. Most of the fractures of ceramic surfaces were cohesive (within resins) and/or interface (at the ceramic surface) failure.
Further aspects of design for distal extension removable partial dentures based on the Kennedy classification
Authors: Ben‐Ur Z. , Shifman A. , Aviv I. , Gorfil C.
Published: March 2003

A supplement to the Kennedy classification of partially edentulous arches for restoration with removable partial dentures has been suggested. Factors affecting denture design relating to the position of the abutment teeth, the symmetry of the edentulous distal extensions, the arch form and the cross‐sectional shape of the residual ridges have been discussed and classified. An understanding of the movement of the denture bases in relation to the influence of these factors makes for a rational approach to removable partial denture design and the treatment of complications observed clinically in removable partial denture wearers.
Bilateral variation of the masseteric myotatic reflex and the silent period in young humans
Authors: Kossioni A. E. , Karkazis H. C.
Published: March 2003

Increased bilateral differences in jaw reflexes have been considered as pathological findings. The aim of this study was to investigate the normal variation between sides in the jaw jerk and the silent period and determine the range of its boundaries, using the present experimental set‐up. Electromyographic data were simultaneously recorded from the right and left masseter muscles by surface electrodes, using a computerized recording and analysis system. The reflexes were elicited by chin taps during mandibular rest and at moderate intercuspal clenching in 20 healthy dentate adults (10 males and 10 females) with a mean age of 26 years. The reflexes were always elicited bilaterally and no overall significant differences were observed between sides for occurrence, latency, duration and amplitude of the jaw jerk and for the latency and duration of the silent period (P>0·05). However, in the individual analysis significant bilateral variation was occasionally recorded, particularly for the jaw jerk at rest and mainly in the amplitude measurements. On the other hand, in the silent period duration measurements individual variation was very limited. Bilateral individual latency differences for the jaw jerk did not exceed 1 ms at rest (x=0·3±0·3 ms) and 0·7 ms at clench (x=0·3±0·2 ms), while latency differences for the silent period did not exceed 0·8 ms for the early type (x=0·4±0·2 ms) and 4·8 ms for the late phase of depression (x=1·9±1·7 ms). Bilateral differences for the silent period duration did not exceed 7·1 ms (x=2·2±2·3 ms) in the early type (simple+early phase of combined types) and 3·3 ms (x=1·5±0·9 ms) in the total duration of the combined types.
Amplitude and frequency spectrum of temporomandibular joint sounds from subjects with and without other signs/symptoms of temporomandibular disorders
Authors: Sano T. , Widmalm S.‐E. , Westesson P.‐L. , Takahashi K. , Yoshida H. , Michi K. , Okano T.
Published: March 2003

Temporomandibular joint (TMJ) sound is one of the most commonly recognized signs in patients with temporomandibular disorders (TMD) but is also frequently seen in asymptomatic individuals. Sound recording is therefore only meaningful if the sounds from a normal healthy joint can be differentiated from those in patients. In this study, the amplitude and power spectrum of the TMJ sounds from symptomatic patients and asymptomatic individuals were recorded and compared. The result showed that TMJ sounds from symptomatic patients had a larger amplitude than sounds from asymptomatic subjects. A significant proportion of sounds had frequencies between 2000 and 3000 Hz. It was concluded that the characteristic amplitude is worthy of further study as a sign of possible diagnostic value. Secondly, the bandwidth of the sensors used at electronic TMJ sound recording should not be less than 3000 Hz.
The effectiveness of element downsizing on a three‐dimensional finite element model of bone trabeculae in implant biomechanics
Authors: Sato Y. , Wadamoto M. , Tsuga K. , Teixeira E. R.
Published: March 2003

More validity of finite element analysis in implant biomechanics requires element downsizing. However, excess downsizing needs computer memory and calculation time. To investigate the effectiveness of element downsizing on the construction of a three‐dimensional finite element bone trabeculae model, with different element sizes (600, 300, 150 and 75 μm) models were constructed and stress induced by vertical 10 N loading was analysed. The difference in von Mises stress values between the models with 600 and 300 μm element sizes was larger than that between 300 and 150 μm. On the other hand, no clear difference of stress values was detected among the models with 300, 150 and 75 μm element sizes. Downsizing of elements from 600 to 300 μm is suggested to be effective in the construction of a three‐dimensional finite element bone trabeculae model for possible saving of computer memory and calculation time in the laboratory.
Effect of water storage on the silanization in porcelain repair strength
Authors: Berry T. , Barghi N. , Chung K.
Published: March 2003

This study examined the long‐term water storage affect of silanization on shear bond strength of composite resin to porcelain. One hundred and sixty square‐shaped specimens were fabricated and sanded flat sequentially with silicone carbide papers. The specimens were then placed into four groups and 16 subgroups of 10 specimens each randomly. Four commercially available silane systems, two one‐mix and two two‐mix, were tested in this study. Teflon tubes with an internal diameter of 2·97 mm and 2 mm in height were filled with a dual cure composite resin (Mirage® FLC), placed on the silanated surfaces and light‐cured for 120 s. Specimens were stored in room temperature water and subjected to shear bond strength testing after 24 h, 1 week, 1 month and 3 month periods of immersion. An Instron Universal testing machine with a crosshead speed of 0·5 mm/min was used for the testing. The mean values of the shear bond strengths ranged from 4·38 MPa (24‐h period) to 23·90 MPa (3‐month period).
anova and Scheffe’ tests were used to analyse data with confidence level at 95%. All groups recorded an increase in bond strength after one week as compared with the 24‐h period (P≪0·05). With the exception of a one‐mix system, all systems showed significantly higher bond strength at 3 weeks as compared with the 24‐h and 1‐week water storage periods. In conclusion, bond strength of composite resin to porcelain resulting from silanization of porcelain increased during the experimental period. The bond strength also varied for different silanes used in this study.
Temporomandibular disorders in Saudi females seeking orthodontic treatment
Authors: Akeel R. , Al‐Jasser N.
Published: March 2003

The aim of this study was to describe the prevalence of signs and symptoms of temporomandibular disorders (TMD) in a group of patients seeking orthodontic treatment. One hundred and ninety one consecutive prospective orthodontic female patients, divided into three age groups of 8, 14 and 18 years, were examined for TMD signs and symptoms and orthodontic treatment need (IOTN). The percentages of signs and symptoms found were 41 and 30%, respectively. No significant association was found between IOTN and TMD signs and symptoms. The youngest age group reported significantly less headache and temporomandibular joint (TMJ) noise. Headache was significantly associated with all TMD symptoms and with tenderness to palpation. In conclusion, the results indicate that malocclusion could not be considered as a primary aetiologic factor for TMD within the age range studied.
The properties of polymerizable luting cements
Authors: Nicholson J. W. , McKenzie M. A.
Published: March 2003

The properties of a polyacid‐modified composite resin and two resin‐modified luting cements have been studied. The polyacid‐modified composite resin had the slowest setting reaction and, in this respect, it did not conform to the current international standard for luting cements. The compressive strength of all of the materials was studied after varying periods of storage from 24 h to 1 year. The polyacid‐modified composite resin showed a distinct dip in strength at 1 month in all of the storage media, but otherwise it showed no significant variation with either age or storage medium. The resin‐modified glass–ionomers showed variation at 24 h with storage medium (deionized water, 0·9% NaCl or 20 mmol dm−3 lactic acid), but thereafter they showed little variation, until 1 year, when Vitremer® luting showed a significant decline in strength in pure water. However, at 24 h and when stored in water, all of the materials had strengths that easily exceeded the minimum requirement of the current standard (70 MPa). They all took up water on storage, with diffusion coefficients ranging from 1·32 to 17·19×10−7 cm2 s−1. These values were found to depend on whether the specimens were stored in pure water or in physiological saline. However, equilibrium water contents varied only slightly between water and saline. The polyacid‐modified composite resin, Dyract‐Cem®, took up the least water, as well as showing the smallest variation in strength with age. By contrast, it was more difficult to mix than the other materials and the high viscosity of the paste led to the formation of voids and other imperfections in the specimens.
Relative solubilities of hybrid ionomers and compomers by acid impingement
Authors: Bapna M. S. , Mueller H. J.
Published: March 2003

The purpose of this investigation was to determine the relative erosion/solubility for hybrid glass–ionomers and a compomer using the jet‐impingement technique with lactic acid of various molarities. The materials studied included Dyract®, Duet®, Vitremer®, Advance®, Fuji‐II LC®, and Fuji‐I®, Ketac Cem® and Modern Tenacin® as the control. Data were analysed using anova and Tukey's comparison test. Results indicated that depth of erosion/solubility with hybrid glass–ionomers and compomers was not measurable by the normal procedure. Similarly, weight changes were not detectable at 0·002, 0·02 and 0·05 m (except for Advance® at 0·05 m). All glass–ionomers materials and the compomer revealed weight changes at 0·1 m after 24 h, in the following increasing order: Dyract®<Fuji‐II LC®=Duet®<Advance®<Vitremer®. It was concluded that weight loss is a better parameter to characterize these new hybrids glass–ionomers and compomers for erosion/solubility by jet‐impingement. In addition, a lactic acid of minimum 0·1 m as a test solution is required to generate 24 h‐data that can be measured in most laboratories and thus used for statistical comparison.
The use of gamma irradiation for the sterilization of enamel for intra‐oral cariogenicity tests
Authors: Amaechi B. T. , Higham S. M. , Edgar W. M.
Published: March 2003

The dose of gamma irradiation sufficient to sterilize enamel samples to be used for intra‐oral cariogenicity tests (ICT) without alteration to the structure or solubility of the enamel was determined. Each bovine incisor used was cut vertically into eight portions and each portion assigned to one of eight groups. Group 1 was used as control while other groups were subjected to respective doses of gamma irradiation from a cobalt‐60 source. Following sterilization, both control and experimental groups were incubated in nutrient broth for 7 days at 37 °C under aerobic and anaerobic conditions. Caries‐like lesions were subsequently produced in each specimen using acidic buffer solution, and mineral loss quantified using transverse microradiography. Data were analysed statistically. There was no significant difference in mineral loss between the control and experimental groups, but the numerical value of mineral loss was lower in groups irradiated with> 4080 Gy, in addition to full sterilization and enamel discoloration to cream colour observed in these groups. Microbial growth was observed in the control group and in groups irradiated with <4080 Gy but no discoloration. With 4080 Gy full sterilization without discoloration was observed. It was concluded that 4080 Gy of gamma irradiation is optimal for sterilization of enamel samples for use in ICT.
Adhesive bonding of noble metal alloys with a triazine dithiol derivative primer and an adhesive resin
Authors: Matsumura H. , Taira Y. , Atsuta M.
Published: March 2003

The purpose of this study was to evaluate the bond strength and durability of a metal adhesive system bonded to noble metal alloys. Disc specimens were cast from type IV gold (type IV, Casting Gold M.C.®), metal–ceramic gold (Au–Pt–Pd, Degudent Universal®), metal–ceramic palladium (Pd–Ga–Co, PTM 88®), silver–indium (Ag–In–Zn, Salivan Hard®) and silver–palladium–copper–gold (Ag–Pd–Cu, S12®) alloys and pure silver (pure Ag). The specimens were air‐abraded with 50 μm alumina, conditioned with a thiol‐based primer designed for noble alloys (V‐Primer®), and then bonded with an adhesive resin (Super‐Bond Opaque Ivory®). Shear bond strengths were determined after repeated thermocycling (4–60 °C, 1 min each, 100 000 cycles). The average bond strengths in MPa (n=8) were 30·9 for the type IV alloy, 29·0 for the Ag–Pd–Cu alloy, 28·0 for the Au–Pt–Pd alloy, 26·3 for the pure Ag, 26·0 for the Pd–Ga–Co alloy and 9·3 for the Ag–In–Zn alloy. The Ag–In–Zn alloy exhibited significantly lower bond strength than the other alloys, whereas the bond strengths of the other four alloys and pure Ag were comparable (P<0·05). It is concluded that the combined use of the thiol derivative primer and the adhesive resin is effective for bonding the noble metal alloys examined, with the exception of the Ag–In–Zn alloy.
Morphological interface between hybrid ionomers and dentin with and without smear‐layer removal
Authors: Abdalla A. I.
Published: March 2003

To evaluate the micromorphological interface between dentin and several hybrid ionomer restoratives, a flat dentin surface was obtained on the occlusal surfaces of extracted human molar teeth after sectioning the enamel with an Isomet saw. Three poly‐acid‐modified composite resins, Compoglass®, Dyract® and F2000®, and two resin‐modified glass–ionomer cements, Fuji II LC® and Photac‐Fil® were applied to the dentin surface. A second section, 2 mm apical from the first one, was made to produce a dentin segment containing the tested materials. Each disc was then split fractured along the dentin/material interface. For the poly‐acid‐modified composites, one half of the disc was stored in 6 mol/L HCl for 48 h to remove the dentin. The other was gently decalcified and deprotenized at the interface between the hybrid ionomer and the dentin. Both halves were then sputtered with gold and examined using SEM. For resin‐modified glass–ionomer, samples were only evaluated at the interface. The three poly‐acid‐modified composite resins showed the formation of hybrid layers and resin tags at the interface to the dentin. Removal of the smear layer significantly improves hybridization of these materials. Also, Fuji II LC® produced a hybrid layer while the Photac‐Fil® showed no evidence of hybridization.
Assessment of whole saliva flow rate in denture wearing patients
Authors: Yurdukoru B. , Terzi̇oğlu H. , Yilmaz T.
Published: March 2003

It has been suggested that salivary flow rate decreases with age. As is known, the presence of a thin salivary film layer is essential for the comfort of the mucosa beneath a denture base and for denture retention. The purpose of this study was to determine the flow rates, viscosity and the pH of resting and stimulated whole saliva before and after prosthetic treatment in complete denture wearing patients. Saliva was collected under clinical conditions between 08·00 and 10·00 hours. The flow rates of whole saliva were measured at three stages: (i) resting and stimulated saliva before prosthetic treatment; (ii) immediately after the first wearing of the complete denture; and (iii) resting and stimulated saliva after 2 or 3 months of wearing the complete denture. Saliva production was stimulated by chewing paraffin wax. Flow rate was calculated as collected volume/collection time. It was found that there was a significant difference between resting and stimulated whole salivary flow rates before and after complete denture wearing.
On‐line computerized diagnosis of pain‐related disability and psychological status of TMD patients: a pilot study
Authors: Yap A. U. J. , Tan K. B. C. , Hoe J. K. E. , Yap R. H. C. , Jaffar J.
Published: March 2003

Temporomandibular disorders (TMD) is a collective term embracing a number of clinical problems, which involve the masticatory musculature, the temporomandibular joint or both. Virtually all theories dealing with the aetiology and treatment of TMD have recognized the importance of psychological factors. This paper reports the development of a computerized on‐line program (NUS TMD v1·1) for the diagnosis of pain‐related disability and psychological status of TMD patients based on Axis II of the research diagnostic criteria (RDC)/TMD (Dworkin, S.F. & LeResche, L. 1992. Journal of Craniomandibular Disorders: Facial Oral Pain, 6, 301), which was developed to redress the lack of diagnostic criteria in TMD research. Methods adopted by RDC/TMD for use in assessing Axis II status include a seven‐item questionnaire for grading chronic pain severity, the Symptom Checklist 90 Revised (SCL‐90‐R) and a jaw disability checklist. A pilot study, based on 37 new TMD patient records, was conducted to study the pain‐related disability and psychological status of TMD patients using this newly developed program. The mean age of the predominantly Chinese population (86.5%) was 32.19 years (range 20–72 years) with a sex distribution of 24 females and 13 males. Most patients (78%) had low disability, with 12 patients having low intensity and 17 patients having high intensity pain. Approximately 73% of the sample population were moderately or severely depressed. Patients that were moderately and severely depressed had significantly higher scores for limitation related to mandibular functioning than normal patients. The three most frequent jaw disabilities were: eating hard foods (84%), yawning (78%) and chewing (65%).
The accuracy with which the human condyle can be expressed in the coordinate system of JAWS3D using a unilateral fiducial marker
Authors: Swintara W. , Johnson C. W. L. , Murray G. M. , Huang B. Y.
Published: March 2003

Previous studies have indicated that the selection of condylar referencing points can significantly influence condylar point trajectories, and the use of radiographically determined condylar points is essential for accurate representation of condylar movement. The aim of this investigation was to determine the accuracy with which the three‐dimensional locations of condylar points could be determined in the coordinate system of the JAWS3D tracking device when an ipsilateral fiducial marker is used. A perspex mandible containing condylar radiographic markers was constructed. A JAWS3D target frame and a fiducial marker, supporting radiographic markers, were secured to the perspex mandible. The image data from computer tomography scans of the condyles and fiducial marker, together with photographs of the fiducial marker and the JAWS3D target frame were used to calculate condylar point coordinates in the JAWS3D coordinate system. These data were then compared with the data obtained by direct measurement of the condylar radiographic markers in the JAWS3D coordinates. The results suggest that a unilateral fiducial marker is sufficient to allow the registration of ipsilateral condylar point coordinates to an accuracy of ∼1.0 mm.
Linear shrinkage of photo‐activated composite resins during setting
Authors: Song Y. X. , Inoue K.
Published: March 2003

The linear shrinkages during setting of five commercially available photo‐activated composite resins were measured using a developed weight‐loaded plate plastometer. Six specimens of thickness ranging from 0·25–2·00 mm were used and the linear shrinkage was measured in three stages: under no‐load or load of 200 or 400 g. Two light‐irradiation times of 20 and 60 s were chosen for each specimen. All measurements were carried out in an air cabinet maintained at either 23 °C or 37 °C. The measuring time of linear shrinkage was 11 min from the start of light‐irradiation. The ratio of apparent linear shrinkage decreased according to the increase in specimen thickness and decreased when load was added during setting. Furthermore, the ratio of linear shrinkage of the specimens increased according to the increase in light‐irradiation time and the ambient temperature of the specimens. When the adsorptivity or stickiness of material to a tooth was high, detectable initial time (Ti) of the linear shrinkage became longer and the magnitude of linear shrinkage to the adherent direction decreased.
Numerical investigation of the factors affecting interfacial stresses in an MOD restored tooth by auto‐meshed finite element method
Authors: Lin Chun‐Li , Chang Chih‐Han , Wang Chau‐Hsiang , Ko Ching‐Chang , Lee Huey‐Er
Published: March 2003

Many researches have addressed the high correlation between the fracture of restored teeth and the prepared cavity geometry. In addition, concerns about bonding versus debonding dental materials from cavity walls and different occlusal force conditions could also alter the mechanical responses in a restored tooth. This study employed an automatic mesh procedure to investigate the mechanical interactions between different interfacial conditions and cavity parameters such as pulpal wall depth under different chewing functions. The results indicated that when occlusal force was applied directly on the tooth, it could increase unfavourable stress dramatically. When interfacial fixation was simulated as the contact condition between the tooth tissue and restorative material, it might increase the fracture potential exponentially compared with the bonded interface. For pulpal wall depth analyses, greater risks of fracture for the remaining tooth were observed in deeper cavity of mesio‐occlusal‐distal (MOD) restorations and the existence of a pulpal wall is essential even it is only 1 mm above the gingival wall.
Induction and 3D reconstruction of caries‐like lesions in an experimental dental plaque biofilm model
Authors: Arnold W. H. , Gaengler P. , Sabov K. , Schmitz I. , Gedalia I. , Steinberg D.
Published: March 2003

The aim of this study was to examine an in vitro dental plaque model for volumetric assessment and 3D reconstruction of experimentally bacterial induced caries‐like lesions. Twenty‐three extracted, impacted human molars were coated with a varnish leaving a 3 × 3 mm window on the smooth surface. The teeth were coated with human saliva and Streptococcus sobrinus 6715 adhered onto the enamel via a succrose dependent mechanism. The coated teeth were incubated for 1, 7, 14 and 28 days. At the end of each incubation period microhardness was measured on three sectioned teeth of each incubation period at the enamel surface and at 450 and 750 μm depth perpendicular to the enamel surface. The enamel surface was investigated by scanning electron microscopy (SEM) prior to embedding and serial sectioning of 12 other teeth. The serial sections were studied with polarization light microscopy to investigate subsurface demineralization. The outlines of the caries‐like lesions were then traced consecutively on transparencies, digitized and three‐dimensionally reconstructed to demonstrate the expansion of the lesion into enamel for volumetric assessment. Microhardness was significantly reduced on the enamel surface after 7, 14 and 28 days incubation. The SEM investigation showed a surface demineralization with dissolution of the prism cores after 28 days incubation. Polarization light microscopy demonstrated caries‐like lesions with an irregular expansion into enamel. The results demonstrate that the described method produces caries‐like lesions which can be used for further experimental studies regarding demineralization and remineralization processes.
Investigation of the relationship between oral parafunctions and temporomandibular joint dysfunction in Turkish children with mixed and permanent dentition
Authors: Sari S. , Sonmez H.
Published: March 2003

The purpose of this study was to investigate the relationship between temporomandibular joint (TMJ) dysfunction, bruxism and oral parafunctions in the permanent and mixed dentition of Turkish children. Examinations were performed on 59 children (26 girls and 33 boys) without TMJ dysfunction and 123 children (54 boys and 69 girls) with TMJ dysfunction in the mixed dentition. In the permanent dentition 89 children without TMJ dysfunction (45 girls and 44 boys) and 123 children with TMJ dysfunction (69 girls and 54 boys) were inducted into this study. The children with oral parafunctions (bruxism, nail biting and thumb/finger sucking) were determined through questionnaires. The Z‐test was used for the analyses of the correlation between variables and differences between the groups. Generally a significant correlation was found between finger/thumb sucking and nail biting and TMJ dysfunction in the mixed dentition and bruxism was observed significantly to be associated with TMJ dysfunction in the permanent dentition (P < 0·05). The evaluation of the results showed that in the mixed dentition groups nail biting was significantly higher in the girls with TMJ dysfunction and finger or thumb sucking was significantly higher in the boys with TMJ dysfunction compared with those without TMJ dysfunction (P < 0·01). In the permanent dentition; bruxism and thumb/finger sucking were significantly higher in girls with TMJ dysfunction higher than those without TMJ dysfunction (P < 0·05). However, thumb/finger sucking was significantly higher in boys without TMJ dysfunction than with TMJ dysfunction (P < 0·05). The results of this study showed that the association of parafunctions and TMJ dysfunction is present in the mixed (thumb/finger sucking and nail biting) and the permanent dentitions (bruxism).
Fracture characteristics of carbon fibre, ceramic and non‐palladium endodontic post systems at monotonously increasing loads
Authors: Ottl P. , Hahn L. , Lauer H.‐CH. , Fay M.
Published: March 2003

A carbon fibre post system, three non‐palladium and one palladium metal post systems, two ceramic post systems, and a metal post system with a ceramic core were studiedin vitro. The control group consisted of root‐filled test teeth without posts. The test teeth were identical artificial roots of an upper central incisor made from a posterior composite whose module of elasticity was similar to that of natural dentine. All posts were cemented in the roots using PanaviaTM21 TC. Subsequently, standardized full crowns were cemented onto all roots. On a universal testing machine, the test teeth were loaded palatally at monotonously increasing loads until root fracture. The highest mean fracture loads were found for the carbon fibre post system (312·5 ± 58·8 N). The fracture load of non‐palladium metal posts (242·3–300·4 N) did not differ significantly from that of the Perma‐dorTMpost (265·9 N), which does contain palladium. Values of 300·3 ± 89·3 N (aluminium oxide ceramics) and 193·5 ± 57·0 N (zirconia ceramics) were found for the ceramic posts. The control group exhibited a fracture load of 228·8 ± 35·7 N. The mean distance between the vestibular end of the fracture gap and the point of force application was between 10·1 ± 2·3 and 14·7 ± 1·2 mm.
Effect of silane primers and unfilled resin bonding agents on repair bond strength of a prosthodontic microfilled composite
Authors: Hisamatsu N. , Atsuta M. , Matsumura H.
Published: March 2003

This study examined the effect of silane primers and bonding agents on bonding between layers of a light‐activated composite material when repaired in the laboratory process. Disk specimens were prepared with the dentin portion of a composite material (Dentacolor DA‐30) and abraded with a silicon carbide rotary cutting instrument. The specimens were conditioned with either one of the two silane primers (Porcelain Liner M and Silicer) or one of the two unfilled resin bonding agents (Dentacolor Opaker liquid and New Metacolor Photo Opaque liquid), or one of four combinations of two primers and two bonding agents. An intact surface with a thin air‐inhibited unpolymerized layer, and an unprimed surface with only silicone carbide abrasion were also used for references. After placement of the enamel portion of the same brand of composite material (Dentacolor SA‐30) on each surface of the dentin material, the specimens were light‐exposed, and stored for 24 h in either dry or wet condition. Shear bond strengths were then determined with a mechanical testing device. The results showed that combined use of a silane primer and a bonding agent generally showed the greatest magnitude of bond strength regardless of material variation. The use of an unfilled resin bonding agent after application of a silane primer (Porcelain Liner M) is recommended to ensure adequate repair bonding between layers of the composite material.
Incidence of oral habits in children with mixed dentition
Authors: BOŠNJAK ANDRIJA , VUČIĆEVIĆ‐BORAS VANJA , MILETIĆ IVANA , BOŽIĆ DARKO , VUKELJA MILKO
Published: March 2003

Summary Recognition and elimination of an oral habit is of utmost importance in the treatment of periodontal disease. It is not probable that the influence of such a factor can lead to the alteration of gingival dimension, but a cofactor role of oral habits in the development of gingival recession has been acclaimed. The purpose of this study was to present cross‐sectional data from an epidemiological study performed in two urban settlements in Zagreb, Croatia. The study was performed in 1025 children, in an attempt to try and discover the incidence of oral habits in children with mixed dentition, aged from 6 to 11 years. About 33·37% of the screened population exhibited oral habits, such as nail and object biting, non‐nutritive sucking, simple tongue thrusting and lip or cheek biting. Chi‐square test analysis showed no statistically significant differences between sex and age groups, a result that does not exclude the oral habits from aetiology of the periodontal pathology. We can conclude that oral habits are a frequent finding, although the cause relation to periodontitis has yet to be cleared completely.