bluuebunny/crossref_metadata_2025 huggingface dataset:
An X-ray Diffractometric Investigation of the Sn-Hg Binary System within the 0-40% Hg Interval
Authors: Soderholm K.-J.M.
Published: November 2010

By use of a precise x-ray diffractometric method and a computer program for parameter determinations (PIRUM), the delta phase of the tin-mercury system was identified. The delta phase appeared to be an orthorhombic structure, existing as a solid solution of mercury in tin in the 15 to at least 40 weight-percentage mercury interval. The diffraction pattern of this phase was almost identical with that of the gamma phase, which explains why its existence has been very difficult to demonstrate with most conventional x-ray diffractometric techniques. The difference between these two phases is mainly related to a slight deformation of the hexagonal structure, causing a small angular change at the corners of the hexagonal structure. This angular change, although small, transforms the hexagonal structure to a structure which should be described as a base-centered orthorhombic structure. Since the delta phase is closer than the gamma phase to the liquidus part of the tin-mercury system at room temperature, it is more likely to be formed when a conventional amalgam sets.
In vitro Modulation of T6 Expression on Gingival Langerhans Cells by Interleukin-1 Inhibitors and ETAF
Authors: Walsh L.J. , Lander P.E. , Seymour G.J. , Powell R.N.
Published: November 2010

T6 antigen is a highly specific marker for human Langerhans cells (LC). Previous studies have demonstrated that Interleukin-1 (IL-1) and an IL-1 inhibitor (ILS) modulate LC T6 expression (T6E) in explant culture. The present study examined the in vitro modulation of T6E by two molecules: epidermal-cell-derived thymocyte-activating factor (ETAF), and a bone-derived protein (BP) implicated in the control of bone homeostasis. The effect of purified ILS was also examined. ETAF mimicked the stimulatory effect of IL-1 on LC T6E, while BP depressed T6E in a manner resembling that seen with ILS. No agents altered Class II (DR and DQ) expression by LC. BP was a specific IL-1 inhibitor, and did not inhibit thymocyte proliferation in the standard IL-1 bioassay in the absence of IL-1. These results demonstrate that molecules resembling IL-1 or ILS can modulate T6E, and implicate locally produced ETAF and ILS in the regulation of T6E in the oral mucosa in vivo.
The Effect of Rate of Increase of Electrical Current on the Sensation Thresholds of Teeth
Authors: Abdel Wahab M.H. , Kennedy J.G.
Published: November 2010

The effect of the rate of increase of electrical current during stimulation of human teeth was examined on clinically sound upper anterior teeth. The teeth were stimulated with a current of 10 msec duration at a frequency of 50 Hz. Eight different rates of current increase were used, viz.: 1, 2, 3, 4, 5, 6, 7, and 8 μa/sec.

The results showed that there was a linear relationship between the sensation threshold and the rate of current increase, and that the threshold increased significantly as the rate of current rise increased.

Slowly increasing current gave more accurate and reproducible results than did rapidly increasing current, and a rate of 2 μa/sec was found to be appropriate for clinical pulp-testing.
Movement of Fibroblasts in the Periodontal Ligament of the Mouse Incisor is Related to Eruption
Authors: Beertsen W. , Hoeben K.A.
Published: November 2010

Movement of fibroblasts in the periodontal ligament of the lower incisor of the mouse was studied by pulse-labeling with tritiated thymidine and proline. 3H-Thymidine was administered to mark the nuclei of the cells in the proliferative compartment near the basal end of the tooth; 3H-proline gave rise to a narrow band of radioactivity in the dentin, which served as a reference line for measurement of eruption. One or three weeks after injection in each animal, the lower right incisor was prevented from further eruption by being pinned to its alveolar process. The animals were killed 0, 1, or 2 weeks later, and their mandibles processed for LM-radioautography. It was found that in the left incisors, which were not inhibited in their eruption, labeled cells in the tooth-half of the periodontal ligament moved incisally at a rate similar to the eruption rate. In the pinned incisors, no further incisal migration could be established. It is concluded that fibroblast migration in the tooth-half of the ligament is strictly coupled to the eruptive process.
Intra-oral Effects on Acid-softened Enamel of NaF Lozenges Administered in Divided Daily Doses
Authors: Corpron R.E. , Clark J.W. , Arnold J. , More F.G. , Merrill D. , Kowalski C.J.
Published: November 2010

The purpose of this investigation was to study the intra-oral effects of multiple daily applications of NaF lozenges upon acid-softened enamel. Bovine enamel slabs were softened with 0.1 mol/L lactate buffer at pH 4.0 for 14 hrs and subsequently mounted in a mandibular removable Hawley appliance. Control slabs were worn for seven days by eight adult male subjects who brushed their natural dentition daily with a fluoride-free dentifrice. Test slabs were exposed to one 0.55-mg NaF lozenge (0.25 mg F) 4x/day for seven days and the natural dentition brushed with a fluoride-free dentifrice. The efficacy of 0.25-mg F lozenges used 4x/day over that of a 1-mg F lozenge administered 1x/day was established by a pilot study with two subjects. Microhardness testing was performed after intra-oral exposure (IOE) and following immersion in 0.01 mol/L lactate buffer containing Ca and P04 for 24 hrs at a pH of 4.0. Fluoride uptake was measured on separate control and test slabs after KOH wash and after acid-resistance-testing (ART). Recovery of microhardness following IOE was 40.9% for controls and 53.9% for treated slabs, while control slabs retained 1.3% resistance to ART, compared with 25.6% for test slabs. The F content of the control slabs was significantly less than that of lozenge-treated and lozenge-treated-ART slabs throughout the depth of the lesion. The F content of the lozenge-treated-ART slabs was significantly less than that of the lozenge-treated slabs only at the 0-5-μm depth. The NaF lozenge-treated enamel lesions demonstrated both significantly greater rehardening and F uptake than did the untreated control enamel lesions.
Effect of Histological Decalcifying Agents on Number and Stainability of Gram-positive Bacteria
Authors: Wijnbergen M. , Van Mullem P.J.
Published: November 2010

In tests of the effects of restorative materials on dental pulp, it is important that one evaluate bacterial contamination, and this is usually done histologically. Preceding the usual paraffin-embedding of hard-tissue specimens for microscopical investigations, decalcification is performed. To study the influence of decalcifying agents (nitric acid, formic acid, and ethylenediamine tetraacetic acid) on the number and Gram-stainability of bacteria, we used a model system consisting of suspensions of formaldehyde-fixed Streptococcus faecalis. The Gram-positive organisms were stored in distilled water, in 4% formaldehyde solution, or in the decalcifying agents for various experimental periods. Counts were made by means of a hemocytometer, and smears were stained with the Brown and Brenn staining method. After periods which are averages for the decalcification of teeth, severe reductions of both the number and the Gram-positive stainability were found. After one week in formic acid, only one out of 15 organisms stained blue. With nitric acid and EDTA, the reductions were fewer. Since only blue-staining bacteria can be detected clearly in tissue sections, the results of these experiments indicate that, with limited numbers of organisms, the risk exists for false-negative scores for decalcified hard-tissue sections.
Dental Papilla Cells Synthesize But Do Not Deposit Fibronectin in Culture
Authors: Thesleff I. , Partanen A.-M. , Kuusela P. , Lehtonen E.
Published: November 2010

The dental papilla cells play a major regulatory role during tooth morphogenesis, and they are the only mesenchymal cells capable of differentiating into odontoblasts secreting dentin. In this paper, we have extended our studies on the behavior of cultured dental papilla cells which have been disaggregated from 17-day mouse embryo teeth. Quite unexpectedly, we observed that these cells, which in vivo are embedded in a fibronectin-rich extracellular matrix, lose all surface-associated fibronectin when cultured as monolayers. Fibronectin was, however, detected intracellularly, and metabolic labeling and immunopreciopitation studies indicated that the dental papilla cells continued to synthesize fibronectin in culture. Furthermore, when purified plasma fibronectin was added at 50 μl/mL to the culture medium, it became incorporated as fibrillar matrix on the surfaces of dental papilla cells. This indicates that the cells are not deficient in cell-surface receptors or other surface-associated molecules which bind fibronectin. When pieces of dental palpillae were cultured as explants, an abundant matrix containing fibronectin was deposited on their surfaces. This matrix was gradually lost as the cells migrated from the explants. Furthermore, when the cells were disaggregated and cultured at high cell density, the cells in the central area of the pellet were covered by fibronectin containing fibrillar structures which were lost as the cells spread out. This indicates that the maintenance of close contacts between the dental papilla cells is required for the assembly of fibronectin into the extracellular matrix.

Three other lineages of mesenchymal cells from the jaws of 11-, 13-, and 17-day-old embryos all developed a fibronectin-containing fibrillar network typical of fibroblastic cells in culture. When the ultrastructure of dental papilla cells was compared with that of gingival mesenchymal cells of 17-day-old embryos, both showed electron-dense material in the cisternae of rough endoplasmic reticulum. On the other hand, only minor amounts of extracellular material could occasionnally be found associated with the dental cells, whereas the gingival cells regularly showed abundant deposits of fibrillar extracellular material.
The Effects of Cheese Snacks on Caries in Desalivated Rats
Authors: Krobicka A. , Bowen W.H. , Pearson S. , Young D.A.
Published: November 2010

Rats that had had their submandibular/sublingual glands removed surgically, and their parotid ducts tied, developed fewer and less severe caries lesions on coronal and root surfaces when fed cheese snacks in addition to a cariogenic diet than when fed additional cariogenic snacks or no additional snacks. The effects of cheese snacks were particularly dramatic on root-surface caries. These observations may be relevant for elderly humans who are most likely to develop root surface caries.

Populations of Streptococcus mutans did not differ among the groups. Actinomyces viscosus was not detected at the end of the experiment in any of the groups. The results of this study demonstrate that cheese exerts a protective effect against coronal and root-surface caries in rats with a severely limited salivary function.
Immunocompetent Cells in the Normal Dental Pulp
Authors: Jontell M. , Gunraj M.N. , Bergenholtz G.
Published: November 2010

The existence and location of various immunocompetent cells in the human dental pulp were investigated. Pulp tissue for analysis was obtained both from clinically intact pre-molars and from third molars without restorations or caries. Frozen and acetone-fixed pulp tissue sections were subjected to indirect immunohistochemistry with monoclonal antibodies to the following cell types: all peripheral T cells, helper/inducer T cells, cytotoxic/suppressor T cells, macrophages, B cells, and Class II antigen-expressing cells. Dendritic cells expressing Class II antigens (HLA-DR,-DQ), indicating a capacity for presentation of antigen to T helper cells, were seen in the odontoblastic layer as well as in the central portions of the pulp tissue. T lymphocytes, divided into helper/inducer and cytotoxic/suppressor cells, were observed in all pulp specimens. B cells were not seen in any of the pulp samples examined. The data demonstrate that the human dental pulp is equipped with immunocompetent cells essential for the initiation of immunological responses.
Identification of Merkel Cells in Oral Epithelium Using Antikeratin and Antineuroendocrine Monoclonal Antibodies
Authors: Ness K.H. , Morton T.H. , Dale B.A.
Published: November 2010

Merkel cells are a rare cell type located at or near the basal lamina of oral epithelia and epidermis. They are associated with nerves, and may function as touch receptors. Merkel cells are difficult to identify by routine light microscopy, but have been identified by electron microscopy and specific antibodies. We demonstrate here that Merkel cells can be identified by immunohistochemistry, using a monoclonal antibody (LK2H11, Lloyd and Wilson, 1983) to neuroendocrine granules, and a monoclonal antibody (35βH11, Gown and Vogel, 1982) to a 54-kD keratin generally located in simple epithelia but not in stratified epithelia.

Human oral tissue was fixed in Carnoy's fixative, and adjacent serial sections were stained with the two antibodies. Individual positively-stained cells were generally located at the bases of rete ridges. Cells in the same position in adjacent sections stained with both antibodies. Essentially all cells (94%) staining for neuroendocrine granules also gave a positive reaction for the 54-kD keratin, evidence that a single Merkel cell contains neuroendocrine granules and the 54-kD keratin. Staining of epithelial sheets of human oral tissues revealed a linear distribution of Merkel cells along the bases of rete ridges.

We conclude that antibodies to simple epithelial keratins and neuroendocrine granules may be excellent immunohistochemical markers for Merkel cells, thus facilitating future studies to examine changes in Merkel cells and their distribution in pathologic conditions. The observation that Merkel cells can be stained with an antikeratin antibody strongly supports the epithelial origin of these cells.
Initial Characterization of a Neutral Metalloproteinase, Active on Native 3/4-Collagen Fragments, Synthesized by ROS 17/2.8 Osteoblastic Cells, Periodontal Fibroblasts, and Identified in Gingival Crevicular Fluid
Authors: Overall C.M. , Sodek J.
Published: November 2010

Analysis of collagenolytic activity in gingival crevicular fluid (GCF) has revealed the presence of an enzyme capable of fragmenting native 3/4 and ¼-collagen cleavage products generated by collagenase. An enzyme with similar activity was also identified in media conditioned by fibroblasts from rat periodontal ligament and gingiva, and by rat osteoblastic cells (ROS 17/2.8, 17/2A, 17/2B). In culture, the enzyme was secreted in a latent form that could be activated by organomercurials. For further characterization of this novel enzyme (MMP-V), the osteoblast proteinase was partially purified. ROS 1712.8 conditioned medium was harvested daily and the 25% - 60% sat. ammonium sulfate fraction chromatographed on an AcA 54 gel filtration column. Latent forms of MMP-V (apparent Mr ~54 k) and collagenase (Mr ~54 k) were resolved from gelatinase (Mr ~76 k) and two collagenase inhibitors (Mr ~62 k, ~36 k). Activated MMP-V degraded native 3/4collagen fragments from collagen types I and II in a step-wise manner and was active on denatured collagen. MMP-V showed a divalent cation requirement, was active at neutral pH, and was inhibited by collagenase inhibitor and fetal bovine serum, but not by serine, thiol, or carboxyl proteinase inhibitors. These properties indicate that MMP-V is a member of the matrix-degrading, neutral-metalloproteinase family of enzymes which include collagenase, gelatinase, stromelysin, and telopeptidase. The enzyme may function in the degradation of collagen fibrils by cleaving proteinase-resistant 3/4-collagen fragments that are stabilized by association with neighboring collagen molecules.
The Surface Area of the Adult Human Mouth and Thickness of the Salivary Film Covering the Teeth and Oral Mucosa
Authors: Collins L.M.C. , Dawes C.
Published: November 2010

The surface area of the mouth was measured to calculate the average thickness of the salivary film which separates the opposing layers of the oral mucosa and which also overlies the dental plaque.

The subjects were 10 adults of each sex, all of whom had essentially a full complement of teeth. Impressions were taken of the upper and lower jaws, the buccal and labial vestibular mucosa, and the ventral surface of the tongue, and stone models were cast. The dorsum of the tongue was assumed to have the same area as the palate plus that of the palatal surfaces of the upper teeth. The six separate areas considered were the teeth, the palate, the buccal and lingual gingival and alveolar mucosa, the buccal and labial vestibular mucosa, the ventral surface of the tongue, including the floor of the mouth, and the dorsum of the tongue. Aluminum foil, of known weight per unit area, was adapted to the models of the different regions of the mouth, and the surface areas were calculated from the weights of the foil. The mean total surface area of the mouth was 214.7 ± 12.9 cm 2, and there was no significant difference due to gender. The teeth, keratinized epithelium, and non-keratinized epithelium occupied about 20%, 50%, and 30% of the total surface area, respectively.

Given that the average volumes of saliva present in the mouth before and after swallowing have been estimated to be 0.77 and 1.07 mL, respectively, it can be calculated that the average thickness of the salivary film in the mouth varies between 0.07 and 0.10 mm. Since we have previously assumed that dental plaque is washed by a relatively thick layer of saliva, the results have important implications with regard to diffusion of substances in and out of dental plaque and with regard to the sensation of oral dryness caused by fluid absorption through the oral mucosa or by salivary evaporation.
A Mixed-culture Chemostat System to Predict the Effect of Anti-microbial Agents on the Oral Flora: Preliminary Studies using Chlorhexidine
Authors: McDermid A.S. , McKee A.S. , Marsh P.D.
Published: November 2010

A mixed-culture chemostat system, composed of nine bacterial species representative of plaque in health and disease, has been assessed as an improved laboratory method of evaluating the likely in vivo effects of antimicrobial agents used in dentistry. The advantages of the system include reproducibility, the long-term stable cultivation of bacteria under controllable conditions, and repeated sampling, for bacteriological and biochemical studies, without disrupting the stability of the community. The effects of (i) the continuous provision of chlorhexidine (CHX) and (ii) three pulses of CHX (final concentration in both experiments = 0.24 mmol/L) on the composition of the chemostat communities were monitored. Only L. casei survived the continuous provision of CHX; the other bacteria were killed and were lost at different rates which generally corresponded to their known sensitivities to CHX. After each CHX pulse, the numbers of bacteria fell markedly. Again, L. casei was least affected, while A. viscosus, B. intermedius, and F. nucleatum were temporarily undetectable but returned to their original levels within 2-4 generation times. Counts of S. mutans were affected more by CHX than those of S. sanguis or S. mitior. The effect of successive pulses of CHX on the viability of some bacteria and on acid production (as measured by pH-fall experiments) decreased, suggesting that adaptation to CHX had occurred. The fact that the in vitro observations paralleled previous clinical findings suggests that the mixed-culture system could be used as a predictive model of the probable effect on the oral flora of new anti-microbial agents prior to expensive trials in animals or human volunteers.
Effects of Rare-earth Filters on Patient Exposure and Image Contrast
Authors: Mauriello S.M. , Washburn D.B. , Matteson S.R.
Published: November 2010

Minimizing patient exposure while maintaining a diagnostically acceptable radiograph is a major goal in diagnostic radiography. Rare-earth filters may be the means to achieve this goal due to their "bandpass effect". The purpose of this study was to examine the image contrast effects and exposure reductions for various thicknesses of aluminum, samarium, gadolinium, gadolinium oxysulfide, and gadolinium oxysulfide added to 2.5 mm of aluminum. Trials were conducted on an intra-oral dental x-ray unit (range, 65 to 90 kVp). When compared with conventional aluminum, all of the rare-earth filters provided lower radiation exposures, with gadolinium in the metallic or oxysulfide form providing the lowest exposures. Samarium, at a thickness of 0.127 mm, yielded the highest image contrast. Gadolinium or gadolinium oxysulfide added to 2.5 mm of aluminum resulted in a slight loss of contrast when compared with conventional aluminum filtration. This loss may not be clinically significant, and when coupled with the reduced exposure afforded by these filters, they become viable as acceptable alternatives to aluminum filtration.
Effect of Incompatibility Stress on the Fit of Metal-Ceramic Crowns
Authors: Anusavice K.J. , Carroll J.E.
Published: November 2010

The interactive effect of coping thickness and a positive thermal contraction mismatch between metal and porcelain on the fit of metal-ceramic crowns has not yet been experimentally determined. Previous studies have suggested that marginal distortion may be due to contraction differences, although finite element analyses indicate that these distortion effects should be negligible.

The marginal gap between metal-ceramic crowns and prepared dies was determined under conditions designed to exaggerate distortion effects. These included the use of thin metal copings (0.1 and 0.2 mm), a chamfer preparation, an alloy with relatively poor creep resistance, and a large thermal contraction mismatch between the alloy and porcelain layers. Gap changes which resulted during porcelain firing cycles were relatively small, but larger marginal discrepancies developed in crowns prepared with a compatible porcelain during grinding and abrasive blasting procedures. This study conclusively demonstrates that incompatibility stress induced by a positive contraction mismatch is not a primary cause of marginal or generalized distortion of metal-ceramic crowns and suggests that external grinding and internal abrasive blasting of crowns are more likely causes of this effect.
Dynamic Creep of Dental Amalgam as a Function of Stress and Number of Applied Stress Cycles
Authors: McCabe J.F. , Carrick T.E.
Published: November 2010

Dynamic creep tests on specimens of dental amalgam gave a relationship between creep (∈), applied dynamic stress (a), and number of applied stress cycles (N) as ∈ = AN (mσ + c) where A, m, and c are constants. This equation can be used to predict creep of amalgam at low levels of stress and extended times. The pattern of results produced for different types of amalgam indicates that the creep process is multifactorial in nature.
Physical Model for Non-steady-state Dissolution of Dental Enamel
Authors: Patel M.V. , Fox J.L. , Higuchi W.I.
Published: November 2010

The purpose of this study was to provide a rigorous theoretical understanding of the dissolution behavior of dental enamel over the entire time-course of demineralization and to simulate by computer an erosion-type caries lesion according to the physical "hydroxyapa tite model".

The appropriate diffusion equations which accountfor simultaneous diffusion and equilibrium of all species in enamel pores, boundary layer, and bulk solution, and which also take into consideration surface reaction kinetics, were employed to allow for calculation of the micro-environmental solution concentration and changes in the min eral density as a function of time and distance within the enamel. This comprehensive physical model for non-steady-state enamel dissolution also explicitly takes into account changes in the diffusivity and the dissolution rate constant as a function of mineral density. Demineralization experiments were conducted in 0.1 mol/L sink acetate buffer (pH = 4.50, μ= 0.50) , with ground bovine dental enamel blocks of known surface area mounted (with beeswax) in a rotating disk apparatus. Mineral density profiles were quantified by means of contact x-ray microradiography. The physical model was used to predict mineral density profiles for given demineralization treatments. The experimental profiles agreed quite well with the predicted profiles, when the effective diffusivity of the enamel was assumed to be a function of porosity and when changes in surface area of the crystallites were taken into consideration.
The Color Accuracy of the Kubelka-Munk Theory for Various Colorants in Maxillofacial Prosthetic Material
Authors: Ma T. , Johnston W.M. , Koran A.
Published: November 2010

The reflectance model developed by Kubelka and Munk was evaluated for agreement in color prediction of thick pigmented samples and for linearity of optical absorption and scattering coefficients with concentration of colorant in maxillofacial elastomer. The colorants tested were generic opacifiers, dry mineral earth pigments, and fibrous colorants. Significant linear relationships were commonly found between the optical coefficients and the concentration of the colorants. These relationships indicated occasional optical interaction between the colorants and the elastomer. Color differences between theoretical and observed colors of the thick samples averaged 2.96, 3.47, and 1.60 for the opacifiers, mineral earth pigments, and fibrous colorants, respectively, when measured using the CIELAB uniform-color space. The agreement between theoretical and observed colors was significantly closer for the fibrous colorants than for the dry mineral earth pigments of the same labeled color.
Measurement of Selection Chances and Breakage Functions During Chewing in Man
Authors: Van Der Glas H.W. , Van Der Bilt A. , Olthoff L.W. , Bosman F.
Published: November 2010

Food comminution in man was studied in terms of intra-oral selection and breakage processes, with a silicone rubber used as a test food, aided by a sieving procedure and simultaneous form- and color-labeling of particles. The subjects chewed on mixtures of particles with a specific form (either cubes or half-cubes). In addition, seven particle sizes, within a range of 1.2 to 8.0 mm, each had a specific color. Damaged cubes or half-cubes revealed their chance of being selected for breakage. The color of the fragments indicated their original size, and thus the breakage distribution of selected particles. The selection chance increased as a power function of particle size. The degree of fragmentation was, in general, maximal for a particle size of about 4 mm. Our double-labeling technique permits a detailed unraveling of anatomical and physiological variables in the chewing process.
Human Dentin Matrix Induces Cartilage Formation in vitro by Mesenchymal Cells Derived from Embryonic Muscle
Authors: Somerman M.J. , Nathanson M.A. , Sauk J.J. , Manson B.
Published: November 2010

Dentin matrix was assayed for its potential to elicit chondrogenesis of mesenchymal cells in vitro. The substratum was prepared by demineralization of human tooth root dentin, while embryonic thigh muscle was used as a source of mesenchymal cells. Formation of chondrocytes from mesenchymal cells occurred in the presence of dentin matrix, and in the same sequence as previously shown with substrata of demineralized bone.
Creep of Amalgam at Low Stresses
Authors: Papadogiannis Y. , Boyer D.B. , Lakes R.S.
Published: November 2010

The creep and recovery, of dental amalgam were studied with a torsional creep apparatus. The purpose was to investigate viscoelastic behavior in a low stress range that might result from normal chewing forces. The creep of specimens up to six months old was also studied. Four types of alloys for amalgam were used: two single-composition sphericals (SCS), an admixture-lathe-cut eutectic (ALE), and a conventional (CON). Constant torque was applied to dumbbell-shaped specimens for three hr and, after the stress was released, recovery was followed for 50 hr. All measurements were made in water at 37°C after storage of the specimens for one week in 37°C water. Creep was also measured at nine intervals an specimens aged from three hr to six months. The SCS amalgams exhibited the least amount of creep, followed by the ALE amalgam. The CON amalgam had the highest creep. The SCS amalgams approached linear viscoelastic behavior in the shear stress range of 0.78-4. 10 MPa at 37°C. They did not exhibit steady-state (viscous) creep at stresses less than 4.10 MPa. Recovery was complete but proceeded more slowly than creep. The ALE and CON amalgams exhibited viscous creep at 1.23 MPa and higher. The steady-state creep rate depended on stress, and the stress exponent ranged from 2.3-3.5, All except the ALE amalgam showed essentially constant creep compliance when aged up to six months, once the amalgamation reaction was completed after 24 to 48 hr. The compliance of the ALE amalgam gradually decreased over the six-month period.
Thermal Diffusivity of Composite Restorative Materials
Authors: Watts D.C. , McAndrew R. , Lloyd C.H.
Published: November 2010

The substantial increases in the filler volume fraction of the current generation of composite resins, and the incorporation of radiopacifying heavy elements in many of these fillers, constitute significant changes which may affect thermal transport properties. Thermal diffusivity has been determined for 21 of these composite materials recommended for anterior and posterior applications. For radiopaque hybrid and for microfine composites, there was, however, only a gradual trend to increased thermal diffusivity with increasing volume fraction of inorganic filler. These diffusivity values were not greatly in excess of the level observed for dentin. Nevertheless, a small group of materials, incorporating substantial amounts of quartz or silicon nitride filler particles, exhibited high rates of thermal diffusion, up to three times the level exhibited by dentin.
Sialochemistry of Whole, Parotid, and Labial Minor Gland Saliva in Patients with Oral Lichen Planus
Authors: Gandara B.K. , Izutsu K.T. , Truelove E.L. , Mandel I.D. , Sommers E.E. , Ensign W.Y.
Published: November 2010

This study was undertaken to determine whether oral lichen planus in otherwise healthy patients is associated with sialochemical abnormalities. Unstimulated and stimulated whole saliva, stimulated parotid saliva, and stimulated labial minor gland saliva were collected from 25 patients with oral lichen planus and from 25 age- and sex-matched controls. Flow rate and salivary concentrations of immunoglobulins A and G, albumin, amylase, lysozyme, lactoferrin, and total protein were determined by standard analytical techniques. Concentrations of inorganic components including sodium, potassium, calcium, chloride, and phosphate were also measured. No significant differences were found between the lichen planus patients and the controls. These findings do not support an association between oral lichen planus and salivary dysfunction in otherwise healthy patients.
Early Microbial Colonization of Permucosal Implants in Edentulous Patients
Authors: Nakou M. , Mikx F.H.M. , Oosterwaal P.J.M. , Kruijsen J.C.W.M.
Published: November 2010

In edentulous patients, the microbial colonization of permucosal implants of sintered hydroxyapatite was studied. Samples were taken from mucosa and dentures before insertion of implants and from supra- and subgingival sites two to 10 weeks after insertion. In total, five patients and 10 implants with clinically healthy peri-implant tissues were studied. The samples were investigated by dark-field microscopy and anaerobic culture.

The supragingival plaque of the implants was dominated by Gram-positive cocci and rods, the subgingival plaque by Haemophilus spp. and Veillonella parvula.

A group of bacteria was found specifically related to the implants: Actinomyces odontolyticus, Peptostreptococcus micros, Haemophilus actinomycetemcomitans, Eikenella corrodens, Capnocytophaga sputigena, and Leptotrichia buccalis. Black-pigmented Bacteroides was not found in any of the examined samples. Spirochetes were observed in denture plaque samples and in supragingival plaque of the implants.

It is concluded that bacteria known as potential periodontal pathogens colonize the permucosal implants in the first weeks after insertion. The presence of these species seems to be dependent on the ecological factors provided by the artificial gingival crevice of the permucosal implants in the edentulous mouth.
Regional Lymph Node Metastasis Created by Partial Excision of Carcinomas Induced in Hamster Cheek Pouch with 9,10-Dimethyl-1,2-Benzanthracene
Authors: Kage T. , Mogi M. , Katsumata Y. , Chino T.
Published: November 2010

The feasibility of using the hamster cheek pouchldimethyl-benzanthracene (DMBA) system as an experimental model of lymphatic metastasis was investigated. Forty male Syrian golden hamsters treated with DMBA were divided into two equal groups-one with surgical excision of their tumors and a control group without tumor excision. In the excision group, the animals received three applicationslweek to the left cheek pouch of 0.3% DMBA in acetone for 14 weeks. Following a three-week observation period, the tumors in the pouch were excised at their base, and the animals were killed after four weeks of further observation. In the control group, the animals were treated for 14 weeks in a manner similar to that used for the excision group, left for seven weeks without treatment, and then killed. Cheek pouches with tumors and cervical lymph nodes were processed for histological examination. All of the animals, both with and without metastasis, had borne squamous cell carcinomas (SCC) in their treated cheek pouches. Histologically, seven out of 16 animals in the excision group showed metastatic deposits of SCC confined to the left cervical lymph nodes, while in the control group, metastasis was not found in any of the 19 animals with SCC in their cheek pouches. The results demonstrate that surgical excision of the hamster cheek pouch carcinoma is efficient in producing unequivocal lymph node metastasis.
Comparison of Pain Associated with Mechanical and Chemomechanical Removal of Caries
Authors: Anusavice K.J. , Kincheloe J.E.
Published: November 2010

Previous studies have indicated that a chemomechanical caries removal system (CRS) has been effective in minimizing the use of conventional mechanical instruments and that it may reduce the need for local anesthesia. In the present study, a comparison of the pain experienced both during treatment with a chemomechanical technique and during conventional caries removal (control) was made for each of 47 patients who initially were not given a local anesthetic. One of two dentists was randomly selected to examine and treat patients with a matched pair of carious teeth, and each pair of teeth was treated in a randomized order with the CRS or control procedure.

Responses to the McGill Pain Questionnaire (MPQ) revealed a significantly higher level of pain (p < 0.025) associated with the conventional treatment compared with the chemomechanical procedure. A significantly greater number of patients (p<0.05) requested local anesthetic for the tooth subjected to the control procedure than for the tooth subjected to the CRS procedure. However, 72.3% of the patients did not request local anesthesia for either treatment, although pain was experienced by these patients in 46.8% of the control teeth and 27.7% of the teeth which received the CRS treatment. Of the 20 pain descriptor categories listed on the MPQ, the sensory categories accounted for the greatest mean number of pain descriptors selected for both the CRS (4.4) and control procedures (8.0), compared with the mean number of descriptors selected from the affective pain categories for the CRS (0.8) and control procedures (1. 0). These results suggest that sensory pain factors are more important than affective pain factors in controlling the overall discomfort of patients and the need for local anesthetic during caries removal and subsequent restorative procedures.
Experimental Observation of Silver and Gold Penetration into Dental Ceramic by Means of a Radiotracer Technique
Authors: Moya F. , Payan J. , Bernardini J. , Moya E.G.
Published: November 2010

A radiotracer technique was used to study silver and gold diffusion into dental porcelain under experimental conditions close to the real conditions in prosthetic laboratories for porcelain bakes. It was clearly shown that these non-oxidizable elements were able to diffuse into the ceramic as well as oxidizable ones. The penetration depth varied widely according to the element. The ratio DAg/DA u was about 103 around 850°C. In contrast to gold, the silver diffusion rate was high enough to allow silver, from the metallic alloy, to be present at the external ceramic surface after diffusion into the ceramic. Hence, the greening of dental porcelains baked on silver-rich alloys could be explained mainly by a solid-state diffusion mechanism.
Proteins in the Enamel Fluid of Immature Porcine Teeth
Authors: Aoba T. , Tanabe T. , Moreno E.C.
Published: November 2010

The fluid was separated from the immature soft enamel of porcine permanent teeth in the secretory stage according to procedures reported previously (Aoba and Moreno, 1987). The protein content of the fluid was about 2.8% w/v; its amino-acid composition was characterized by high contents of Pro, Glx, Leu, and His, showing composition similar to that of the 20 kilo-dalton (kd) amelogenin or its C-terminal segments. The two major protein species in the fluid had apparent molecular weights of 13 kd and 11 kd, as determined by SDS electrophoresis; the N-terminal residue of the former was Leu, while that of the latter was Ala. The C-terminal sequence of both of them was -Met-Phe-Ser. By comparison with the published sequence of 20-kd porcine amelogenin, it is concluded that the main fluid constituents were derived by cleavages of N-terminal segments from the 20-kd amelogenin.
Failure Stress Criteria for Composite Resin
Authors: De Groot R. , Peters M.C.R.B. , De Haan Y.M. , Dop G.J. , Plasschaert A.J.M.
Published: November 2010

In previous work (Peters and Poort, 1983), the stress distribution in axisymmetric models of restored teeth was analyzed by finite element analysis (FEA). To compare the tri-axial stress state at different sites, they calculated the Von Mises equivalent stress and used it as an indication for weak sites. However, the use of Von Mises' theory for material failure requires that the compressive and tensile strengths be equal, whereas for composite resin the compressive strength values are, on the average, eight times larger than the tensile strength values. The objective of this study was to investigate the applicability of a modified Von Mises and the Drücker-Prager criterion to describe mechanical failure of composite resin. In these criteria, the difference between compressive and tensile strength is accounted for. The stress criteria applied to an uni-axial tensile stress state are compared with those applied to a tri-axial tensile stress state. The uni-axial state is obtained in a Rectangular Bar (RB) specimen and the tri-axial state in a Single-edge Notched Bend (SENB) specimen with a chevron notch at midspan. Both types of specimens, made of light-cured composite, were fractured in a three-point bend test. The size of the specimens was limited to 16 mm x 2 mm x 2 mm (span, 12 mm). Load-deflection curves were recorded and used for linear elastic FEA. The results showed that the Drücker-Prager criterion is a more suitable criterion for describing failure of composite resins due to multi-axial stress states than are the Von Mises criterion and the modified Von Mises criterion.
Factors Affecting Estimation of Dental Amalgam Mercury Exposure from Measurements of Mercury Vapor Levels in Intra-oral and Expired Air
Authors: Mackert J.R.
Published: November 2010

Several investigators have attempted to assess the extent of mercury exposure from dental amalgam restorations through the use of mercury vapor measurements of intra-oral or expired air. The sampling times and flow rates of the mercury vapor analyzers used in intra-oral measurements are not comparable with physiological inhalation times or flow rates of air through the mouth during inhalation. Analysis of the assumptions and measurement techniques employed in previous attempts to estimate mercury exposure from amalgam restorations shows that adequate compensation had not been made for these measurement parameters. Calculation of the mercury vaporization rates responsible for the mercury vapor concentration values previously reported enabled the daily dose of mercury to be estimated for subjects with various numbers of amalgam restorations. The corrected estimates for daily dose of mercury from amalgam restorations are a factor of sixteen lower than those previously reported.
Distribution of Antigenic Determinants Between Actinomyces viscosus and Actinomyces naeslundii
Authors: Firtel M. , Fillery E.D.
Published: November 2010

A total of 18 monoclonal antibodies was raised against whole cells of Actinomyces viscosus and Actinomyces naeslundii. The monoclonal antibodies were used to determine the cross-reacting patterns among 26 strains of these species. Eleven different antigenic determinants were found. The specificity profiles of the antibodies indicated that the antigenic determinants of A. viscosus and A. naeslundii were arranged in a complicated mosaic. Extensive cross-reactions occurred between A. viscosus strains and strains of "typical" and "atypical" A. naeslundii . However, cross-reactions were rare between the two groups of A. naeslundii. A. viscosus appears to occupy a "middle position" between the two A. naeslundii groups.

In addition to their value in seroclassification, some of the monoclonal antibodies were found to be useful in the identification of these species. One monoclonal antibody appeared to be selective for the "typical" A. naeslundii group. A. viscosus and "atypical" A. naes lundii-specific antibodies were also found, though they did not label every strain in their respective clusters. A. viscosus detection might be improved if mixtures of monoclonal antibodies were used.
Sialographic Images of Pathological Changes in the Mouse Parotid Gland
Authors: Domon M. , Kurabayashi T. , Shiga Y.
Published: November 2010

In order to correlate pathological changes of mouse parotid glands with their sialographic images, we conducted studies on mice with known pathological changes: mice with Stensen's duct ligated, NZB mice with a systemic auto-immune disease, and aged mice. The sialographic images were found to be specific for the pathological changes: The glands after ligation of Stensen's duct were characterized by dilated, large excretory ducts with a reduced system of peripheral ducts; the glands of NZB mice showed lobular leakage of the contrast medium from small excretory ducts; and the glands of aged mice showed a great reduction in the ductal system. It is concluded that sialography yields useful information on the pathological changes of the ductal systems in the mouse parotid gland.
Gallotannins Inhibit Growth, Water-insoluble Glucan Synthesis, and Aggregation of Mutans Streptococci
Authors: Wu-Yuan C.D. , Chen C.Y. , Wu R.T.
Published: November 2010

During screening for anti-plaque agents of plant origin, ethanolic extracts from Melaphis chinensis (Bell), the Chinese Nutgall, exhibited strong inhibition of glucosyltransferase (GTF), in vitro adherence and glucan-induced agglutination of Streptococcus mutans 3209 and S. sobrinus B13. More than 91% inhibition of water-insoluble glucan synthesis from sucrose by GTF was noted at a concentration as low as 7.8 μg/mL. Bactericidal effects on other mutans streptococci, S. salivarius, and Actinomyces viscosus were also evident. Through chemical fractionation and analyses, along with bioassays, the active components were identified as gallotannins.
The Acoustical Characteristics of the Normal Temporomandibular Joint
Authors: Gay T. , Bertolami C.N.
Published: November 2010

Both clinical and empirical evidence suggests that the "normal" temporomandibular joint produces noise during function. The purpose of this study was to determine the conditions under which these noises might arise. Joint sounds and mandibular movements were recorded simultaneously from 200 adults who had no previous history or present symptoms of TMJ pain or dysfunction. The joint sounds were recorded bilaterally by means of two separate miniature vibration transducers mounted on a common headband, and incisal point mandibular movements were measured by a magnetometer tracking system. Recordings were made while each subject opened and closed the mouth, first in a natural and comfortable manner, and then to maximum displacement. Two types of measurements were made: the appearance, onset, and duration of joint-propagated sounds in relation to relative mandibular position; and the spectral properties of the detected sounds. The results of this study showed that for natural opening and closing movements of the mandible, the "normal" TMJ was silent for all age groups. However, for the maximum displacement condition, detectable sounds appeared at the points of maximum displacement in both the opening and closing phases of the cycle in over 80 percent of the subjects. However, these sounds were, as a class, substantially longer than, and spectrally distinct from, abnormal joint sounds, suggesting that they arise from a distinct physical substrate.
Degradation of Starch and its Hydrolytic Products by Oral Bacteria
Authors: Glor E.B. , Miller C.H. , Spandau D.F.
Published: November 2010

Selected strains of oral bacteria were analyzed for their ability to degrade wheat starch, maltose, maltotriose, and maltoheptaose. S. sanguis IUOM-11M and JC804, S. mutans 6715, S. salivarius IUOM-8, A. viscosus IUOM-62, and A. naeslundii ATCC 12104 degraded all four substrates. S. mutans NCTC 10449 degraded starch, maltose, and maltotriose, while A. viscosus ATCC 15987 degraded starch and maltose, and S. sanguis SS34 degraded only maltose. L. casei IUOM-14 did not degrade any of the substrates. Analysis of starch degradation products from S. sanguis IUOM-11M and A. viscosus IUOM-62 demonstrated oligosaccharides, maltose, and trace amounts of glucose for the former and oligosaccharides, maltotriose, and maltose for the latter. S. sanguis IUOM-11M α-glucosidase (EC 3.2.1.20) demonstrated a pH optimum of 6.5 and greatly enhanced activity from maltose-cultured cells as compared with cells cultured in glucose or fructose. The presence of fructose in the growth medium prevented this enhancement of activity by maltose. Maltose inhibited sucrose-dependent synthesis of S. sanguis IUOM-11M insoluble polysaccharide and both primer-dependent and primer-independent synthesis of soluble polysaccharide. Maltoheptaose inhibited primer-dependent but not primer-independent soluble polysaccharide synthesis. Several oral bacteria have the ability to hydrolyze starch and to degrade further the products to acidogenic substrates. These products may also inhibit sucrose-dependent synthesis of polysaccharides, which enhances the production of the acidogenic substrate fructose. The results add further support to the growing body of evidence suggesting that caries-promoting properties of starch may be expressed only when starch is present in diets containing sucrose.