bluuebunny/crossref_metadata_2025 huggingface dataset:
Shear Bond Strength of Light-cured Glass Ionomer to Enamel and Dentin
Authors: McCaghren R.A. , Retief D.H. , Bradley E.L. , Denys F.R.
Published: November 2010

The shear bond strengths of a light-cured glass-ionomer cement to enamel and dentin were determined with use of extracted human maxillary permanent canines and molars. Bonding sites on the ground, etched enamel and ground dentin surfaces were demarcated by the punching of a hole, 3 mm in diameter, in an adhesive tape. The mixed glass-ionomer cement was transferred to the demarcated site, cured by exposure to visible light for 30 s, and the cement surface treated with Scotchprep Dentin Primer followed by Scotchbond 2 Light Cure Dental Adhesive. The embedded teeth were positioned in an assembly apparatus, and Silux composite was bonded to the glass-ionomer-cement surfaces. The specimens were disassembled after 15 min and subjected to a shear load (in an Instron machine) immediately after disassembly; after storage in water at 37°C for 24 h, without and with temperature cycling; and after storage in water for four weeks, without and with temperature cycling. The shear bond strength of the glass-ionomer cement to etched enamel was in the order of 12 MN. m-2, and to dentin it was 9 MN.m -2. Temperature cycling and duration of storage had no adverse effect on the shear bond strength. The enamel and dentin aspects of fractured test specimens were examined, and the percentage of the bonding area that failed in the cement was estimated. Most of the test specimens failed partly at the enamel and dentin interfaces and within the glass-ionomer cement.
A Scanning Electron Microscopic Investigation of Bonding of Methacryloyloxyalkyl Hydrogen Maleate to Etched Dentin
Authors: Fukushima T. , Horibe T.
Published: November 2010

Three types of methacryloyloxyalkyl hydrogen maleates-2-(methacryloyloxy)ethyl hydrogen maleate (2MEM), 1-(methacryloyloxymethyl)ethyl hydrogen maleate (MMEM), and 1-(methacryloyloxymethyl)propyl hydrogen maleate (MMPM)-were prepared for use as bonding agents. The relationships between the thickness of an acid-proof dentin layer and the bond strength and chemical structure of the synthesized monomers were investigated. The bond strengths of 2MEM/composite system to dentin treated with either 37% phosphoric acid solution or 10% citric acid-3% ferric chloride solution (10-3 solution) were superior to those of the others. The acid-proof dentin layer for all bonding agents containing the synthesized monomers at the resin-dentin interface was clearly visible in a scanning electron microscope, regardless of the types of dentin etching agents used. After treatment of the dentin with the phosphoric acid solution, the layers of 2MEM, MMEM, and MMPM were 5-6 μm, 3-4 μm, and 2-3 μm thick, respectively. When the dentin was treated with the 10-3 solution, the layer for each bonding agent was approximately 1 μm thick.
Quantitative Radiographic Measurement of Dentinal Lesions
Authors: Heaven T.J. , Firestone A.R. , Feagin F.F.
Published: November 2010

The purpose of this investigation was the comparison of the precision and accuracy of two reference ramp techniques for the quantification of radiographic density changes in teeth. Radiographs (65 kVp, 10 ma, 1 s, and intra-oral ultraspeed film) of transverse sections from extracted permanent human molars were made before and after dentinal lesions were created. Each radiograph contained the image of a tooth section and the aluminum reference ramp. Method A used the image of the ramp on both the before- and after-lesion radiographs, and method B used the image of the ramp only on the before-lesion radiograph. Three groups of lesions (0.525-mm diameter, n = 11; 0.675-mm diameter, n = 9; and the 0.525-mm holes enlarged to 0.675 mm) were measured radiographically by each technique and by direct planimetry of the lesions. Radiographic method B produced results in close agreement with the planimetric measurements. Method B differentiated (p<0.05) between groups that had a mean planimetric size difference of 0.10 mm (equivalent to a change in density difference of 0.6%). These density change measurements are in absolute units of mm of aluminum that can be compared between lesions and between samples. This technique may prove useful for the quantification of changes in mineral density of caries lesions detectable in longitudinal radiographic records.
Cellular Roles in Physiological Root Resorption of Deciduous Teeth in the Cat
Authors: Sasaki T. , Shimizu T. , Watanabe C. , Hiyoshi Y.
Published: November 2010

This study has attempted to assess the importance of mesenchymal cells, fibroblasts, cementoblasts, and mononuclear phagocytes (i.e., macrophages) in physiological root resorption of feline deciduous teeth. Deciduous incisors of three- to six-month-old kittens undergoing root resorption were investigated by means of electron microscopy. In an early phase of root resorption, the resorption organ consisted of many fibroblasts and relatively few macrophages and odontoclasts, the last with a wide, clear zone and narrow, immature, ruffled border. In the active phase of root resorption, the resorption organ contained many odontoclasts with a well-developed ruffled border and a reduced clear zone, cementoblasts, fibroblasts, macrophages, neutrophils, and many blood vessels. Cementoblasts were present usually on the resorbing dentin surface adjacent to odontoclasts and, in many cases, these cells communicated with each other via gap junctions. Cementoblasts frequently extended broad cell processes with secretion granules and with phagosomes containing collagen fibrils into the dentinal tubules exposed to resorption lacunae. Some macrophages exhibiting a clear zone-like structure also appeared on resorbing dentin surfaces. In the resting phase of root resorption, the dentin surface was covered mostly with cementoblasts resembling bone lining cells. There was an occasional macrophage, but no odontoclasts were observed during this phase. During removal of the periodontal ligament concomitant with root resorption, many fibroblasts phagocytosed mature collagen fibrils, as well as amorphous fluffy material. These results suggest that these mesenchymal cells, as well as odontoclasts, are essential for the cellular removal of dental hard and soft tissues during shedding of feline deciduous teeth.
A Biochemical and Immunohistochemical Study of the Proteoglycans of Alveolar Bone
Authors: Bartold P.M.
Published: November 2010

The purpose of this investigation was to study the proteoglycans in alveolar bone of three animal species. Alveolar bone was obtained from humans, pigs, and rabbits. Portions were fixed, sectioned, and stained with monoclonal antibodies against keratan sulfate and chondroitin sulfate. In other samples, biochemical analyses were performed. After removal of the organic matrix by 4 mol/L guanidinium HCl extraction in the presence of proteinase inhibitors, proteoglycans in the mineralized matrix were extracted with 4 mol/L guanidinium HCI/0.5 mol/L EDTAlproteinase inhibitors, and characterized on the basis of their glycosaminoglycan content (cellulose acetate membrane electrophoresis), charge (DEAE-Sephacel and hydroxylapatite chromatography), size (Sepharose CL-6B chromatography and agarose/ polyacrylamide gel electrophoresis), and amino acid content. The results indicated that keratan sulfate could be detected immunohistochemically and biochemically in rabbit bone only. The predominant glycosaminoglycan in pig and human alveolar bone was chondroitin sulfate, although some hyaluronate, dermatan sulfate, and heparan sulfate were also detected. The proteoglycans were found to be slightly smaller than gingival proteoglycans, but similar to those in cementum, dentin, and other bones. In addition to intact proteoglycans, some free glycosaminoglycan chains were also extracted from the mineralized matrix. Amino acid analyses showed some subtle differences between alveolar bone proteoglycan and those of the soft tissues of the periodontium.
Natural History of Periodontal Disease in Adults: Findings from the Tecumseh Periodontal Disease Study, 1959-87
Authors: Ismail A.I. , Morrison E.C. , Burt B.A. , Caffesse R.G. , Kavanagh M.T.
Published: November 2010

The purpose of this epidemiological study was to estimate the degree of change in periodontal attachment level in a sample of adults examined in 1959 and 1987 in Tecumseh, Michigan. Out of 526 individuals between the ages of five and 60 years in 1959, a sample of 325 resided within an 80-km-radius area in 1987. Of those, 167 were re-examined. Loss of periodontal attachment (LPA) was determined with a Michigan #0 probe on four tooth sites (disto-buccal, mid-buccal, mesio-buccal, mid-lingual) for all teeth present. Of the individuals contacted, 28 had lost all their teeth during the 28 years. Of the 167 adults examined, two refused periodontal probing. Out of the 165 adults with LPA measurements in 1987, only 22 (13.3%) had an average increased loss of 2 mm or more per person between 1959 and 1987; five adults (3.0%) had an average LPA increase of 3 mm or more, and only two adults (1.2%) had an average LPA increase of 4 mm or more. The attachment level in 59.3% of all the tooth sites examined in 1959 in the 165 individuals either did not change or changed within ± 1.0 mm. On the basis of bivariate analyses, the individuals with high LPA increase (≥2 mm) had the following characteristics significantly different from those with low LPA increase: They were older, smoked, had tooth mobility at baseline, higher gingivitis, plaque, calculus, and tooth mobility scores at follow-up, lower education level, and irregular dental attendance. However, in logistic regression analyses, only the following risk markers remained significantly associated with high LPA increase: age, smoking, and presence of tooth mobility.
Prevention of Population Shifts in Oral Microbial Communities in vitro by Low Fluoride Concentrations
Authors: Bradshaw D.J. , McKee A.S. , Marsh P.D.
Published: November 2010

A continuous culture system has been used to study the effects of low (sub-MIC) levels of sodium fluoride on the stability and metabolism of a defined oral microbial community. The microflora was also subjected to glucose pulses at pH 7.0, with and without subsequent pH control. At pH 7.0, a continuous supply of 1 mmol/L NaF reduced slightly the viable counts of the oral microflora, although their proportions were relatively unaffected. At pH 7.0, during glucose pulsing, 1 mmol/L NaF prevented the rise in proportions of A. viscosus and reduced the levels of B. intermedius. Glucose pulsing without pH control and in the absence of fluoride markedly inhibited the growth of many species, and L. casei, V. dispar, and S. mutans predominated in the culture. Fluoride (1 mmol/L), either pulsed with the glucose or provided continuously, reduced both the rate of change and the degree of fall in pH, and in doing so prevented the enrichment of S. mutans in the culture. Fluoride also reduced the pH-mediated inhibition of other members of the oral community, although S. sanguis was inhibited even further. Thus, even sub-MIC levels of fluoride may have a beneficial anti-bacterial effect on dental plaque by interfering with acid production. This would reduce the pH-mediated disruption to the balance of the microflora and suppress the selection of S. mutans.
The Relationship between Composition and Properties of Posterior Resin Composites
Authors: Chung K.H.
Published: November 2010

The effects of filler concentration and resinous components on the properties of highly filled composites were determined for prediction of the durability of the restorative resins. Resinous components of seven proprietary light-cured posterior resin composites were extracted by chloroform solvent and examined by the Fourier Transform Infrared (FTIR) method. Filler concentration was determined by the thermogravimetric method. Diametral tensile strength, Knoop hardness, and Barcol hardness tests for the composite, as well as extracted resinous matrix, were performed by standard experimental procedures. Toothbrush abrasion test of the resin composites was evaluated by a toothbrushing machine giving the equivalent of five years' toothbrushing and examined with a roughness meter. The degree of conversion of resin composites ranged from 43.5 to 73.8%. The volume fraction of filler varied from 58.2% to 74.2%. The ranges of diametral tensile strength and Knoop and Barcol hardness numbers obtained were 39.8 MPa to 60.0 MPa, 41.8 to 81.9, and 76.3 to 89.2, respectively. Signiftcant correlations (p<0.01) were obtained between filler fraction and diametral tensile strength (r = 0.89, S.E. = 3.66) and between filler fraction and Knoop hardness number (r = 0.89, S.E. = 8.39). The increase in strength with increased filler concentration might be related to filler/matrix bonding.
Serum Antibody Response to Antigens of Oral Gram-negative Bacteria by Cats with Plasma Cell Gingivitis-Pharyngitis
Authors: Sims T.J. , Moncla B.J. , Page R.C.
Published: November 2010

The etiology of a form of periodontal disease in domestic cats known as plasma cell gingivitis-pharyngitis is not understood. Actinobacillus actinomycetemcomitans and Bacteroides species have been strongly implicated as the cause of periodontitis in humans and other mammalian species, and most affected patients manifest serum antibodies reactive with the infecting bacteria. We and others have isolated Bacteroides species from the oral flora of cats. Using enzyme-linked immunosorbent assay (ELISA) and immunoblot procedures, we measured serum antibodies in affected and control cats reactive with human isolates of A. actinomycetemcomitans, B. gingivalis, and B. intermedius, and purified lipopolysaccharide (LPS) from these and other species, and Bacteroides of cat origin. Affected cats had serum antibody titers reactive with these Gram-negative anaerobic bacteria that were significantly elevated relative to those of normal control cats. The quantitatively major antigens recognized by cat serum antibodies are proteins; this contrasts sharply with serum antibodies from humans with juvenile periodontitis, where LPS is the quantitatively major antigen fraction. Our data support the idea that plasma cell gingivitis-pharyngitis in cats may have a bacterial etiology, and that Gram-negative anaerobes similar to those that cause periodontitis in humans and other mammals may be involved.
Distribution and Prevalence of Mutans Streptococci in the Human Dentition
Authors: Lindquist B. , Emilson C.G.
Published: November 2010

The prevalence of mutans streptococci was determined in 14,859 samples of plaque from all available tooth surfaces in 114 subjects. The clinical examination included location of incipient caries lesions, fillings, and crowns. Mutans streptococci were detected on 40% of all tooth surfaces. The frequency distribution of mutans streptococci and the level of colonization showed a decreasing gradient from molars to incisors for buccal, lingual, occlusal, and approximal surfaces. The location and number of approximal restorations were closely related to the colonization level of mutans streptococci except for second and third molars. Restored surfaces tended to be more colonized by mutans streptococci than sound surfaces, except for occlusal surfaces. A high prevalence of mutans streptococci was found in plaque samples from tooth-colored fillings, especially on buccal and lingual surfaces.
Effects of Fluoride on Matrix Proteins and Their Properties in Rat Secretory Enamel
Authors: Aoba T. , Moreno E.C. , Tanabe T. , Fukae M.
Published: November 2010

This publication concerns the selective adsorption of rat enamel proteins onto hydroxyapatite, their solubility in aqueous solutions, and the effect that systemic fluoride has on these properties. The enamel proteins used as adsorbates were extracted in 0.5 mol/L acetic acid from the secretory enamel of the upper and lower incisors of SD rats (females, 200-220 g body weight). Equilibration of the proteins with hydroxyapatite was performed in two solutions: (i) 50 mmol/L acetate buffer at pH 6.0 and 0°C, and (ii) 50 mmol/L Tris buffer containing 4 mol/ L guanidine at pH 7.4 and room temperature. Enamel was dissected from animals, which were given either de-ionized water (control group) or water containing 25, 50, 75, or 100 ppm fluoride as NaF for four weeks. From these enamel samples, the proteins were extracted in sequence with 160 mmol/ L NaCI and 3 mmol/L phosphate (pH 7.3), 50 mmol/L carbonate buffer (pH 10.8), and finally, with 0.5 mol/L acetic acid for dissolution of the enamel mineral. The F, Ca, and P contents of the various enamel samples were determined. The results showed that: (i) The amelogenin having a 26-kD molecular mass on SDS-PAGE displayed the highest adsorption affinity onto the apatite crystals among the amelogenins; (ii) the same selective adsorption onto the crystals was also observed for the amelogenins separated from the teeth of the animals ingesting fluoride; (iii) the amelogenins can be classified into two groups, neutral-soluble moieties (14-15 kD) and alkaline-soluble moieties (19-28 kD), by the use of solutions having ionic strengths of about 160 mmol/L; and (iv) with regard to the electrophoretic patterns, quantities, and amino acid composition of these two groups of amelogenins, no major differences were obtained between the control group and any groups of animals ingesting fluoride, although the fluoride substitution into enamel mineral increased proportionally with an increase in fluoride concentration in the drinking water, and the incisors from animals in the 75 and 100 ppm F treatment were distinctively brittle. All the foregoing results, as well as those previously reported, indicate that possible functional roles of the amelogenins in early enamel mineralization are common to rat and porcine models, and that the fluoride administration at the doses tested, or the resulting incorporation of fluoride in the forming enamel mineral, caused only a marginal effect, if any, on the properties and degradation processes of amelogenins at the secretory stage of rat amelogenesis.
Facts and Artefacts in Research on Human Dental Plaque Fluid
Authors: Tatevossian A.
Published: November 2010

In 1966, Jenkins suggested that the plaque fluid environment was likely to have higher concentrations of extracellular solutes than was apparent from analyses of total plaque concentrations. Early work on plaque fluid confirmed this contention, but some artefact was also generated by the prolonged centrifugation used for separation.

The solute concentrations in plaque fluid mostly exceed those in saliva or crevicular fluid. Thus, the environmental conditions are distinctly different from those based on the assumption that saliva readily permeates films of dental plaque. In contrast, the presence of serum proteins suggests a crevicular input to plaque fluid. These data suggest that exchange between dental plaque and its environment is apparently restricted. Diffusion rates measured in dental plaque by different methods do not agree on how restricted it is. However, measuring diffusion in plaque introduces artefacts in packing density, a major determinant of the diffusion rate.

The conditions used for collection and analysis have been reported to produce artefactual changes in plaque fluid potassium, a predominantly intracellular ion. Measurements of predominantly extracellular ions, such as calcium, are no less prone to artefact, whether based on ion-selective electrodes or on total calcium.

We have much to learn about the fluid environment of the teeth and about dynamic changes in plaque fluid composition and properties during perturbations. Such information can give insights into pathological processes such as tooth demineralization and dental caries, calculus formation, and gingival inflammation.
Micro-analysis of Plaque Fluid from Single-site Fasted Plaque
Authors: Vogel G.L. , Carey C.M. , Chow L.C. , Tatevossian A.
Published: November 2010

Despite the site-specific nature of caries, nearly all data on the concentration of ions relevant to the level of saturation of plaque fluid with respect to calcium phosphate minerals or enamel are from studies that used pooled samples. A procedure is described for the collection and analysis of inorganic ions relevant to these saturation levels in plaque fluid samples collected from a single surface on a single tooth. Various methods for examining data obtained by this procedure are described, and a mathematical procedure employing potential plots is recommended.
Interactive Effects Between Cytokines on PGE Production by Human Periodontal Ligament Fibroblasts in vitro
Authors: Saito S. , Ngan P. , Saito M. , Lanese R. , Shanfeld J. , Davidovitch Z.
Published: November 2010

Mononuclear cell production of cytokines that stimulate fibroblast production of prostaglandin E (PGE) is an important mechanism by which mononuclear cells regulate fibroblast function. The objective of this investigation was to determine the effects of the cytokines interleukin 1β (IL-1β), interleukin la (IL-1α), tumor necrosis factor a (TNF-a), and interferon γ (IFN--y), alone or in paired combinations, on PGE production by near-confluent human periodontal ligament (PDL) fibroblasts in vitro. Premolars extracted in the course of orthodontic treatment were used for this study. Fibroblast cultures, free of epithelial cells, were obtained after the fourth subculture by the use of accurately-timed trypsin treatment. Cells in the fourth to sixth passage, incubated in DMEM supplemented with 10% equine serum, were used for these experiments. Cells (1 x 105) were seeded in 12- x -75-mm tissue culture tubes and incubated with various doses of IL-1β, IL-la, TNF-a, and IFN-γ, alone or in specific combinations, for 15 min, two, 12, 24, and 72 h. PGE concentrations in the media were measured by radio-immunoassay. The results showed that human PDL fibroblasts responded to the administration of cytokines by an elevation in the synthesis of PGE in a dose- and time-related fashion. The increase in PGE production was inhibited by the addition of indomethacin. The interactions between these cytokines varied in degree, depending on the particular combinations of cytokines. In addition, the administration of cytokine combinations was found to be additive, synergistic, subtractive, or suppressive on the production of PGE by PDL fibroblasts, depending on the duration of incubation. These experiments demonstrate the importance of the consideration of the interplay between cytokines produced by mononuclear cells on the mechanisms that regulate the functions of PDL fibroblasts.
Inhibitory Effect of Human Plasma and Saliva on Co-aggregation Between Bacteroides gingivalis and Streptococcus mitis
Authors: Nagata H. , Murakami Y. , Inoshita E. , Shizukuishi S. , Tsunemitsu A.
Published: November 2010

The effect of human plasma and saliva on co-aggregation between Bacteroides gingivalis and Streptococcus mitis was studied by means of a turbidimetric assay. The co-aggregation activity was obtained from the maximum slope of the absorbance vs. time curve. Its dependence on pH, temperature, and ionic strength was examined, and the number of Bacteroides cells in relation to the number of Streptococcus cells resulting in optimal co-aggregation was established. Co-aggregation inhibition experiments showed that the co-aggregation activity was inhibited by 1-arginine and 1-lysine, although the activity was unaffected by the sugars tested. Human plasma and saliva were able to inhibit the co-aggregation in a dose-dependent reaction. Plasma exhibited the most potent inhibitory activity in these fluids. Fibrinogen was the most potent inhibitor of the plasma-derived proteins tested. These data suggest the possibility that the oral fluids may modulate the attachment of B. gingivalis to Gram-positive bacteria in periodontal pockets.
The Influence of Sucralose on Bacterial Metabolism
Authors: Young D.A. , Bowen W.H.
Published: November 2010

Sucralose (1',4',6' trideoxy-trichloro-galactosucrose) is a nontoxic, intensely sweet sucrose derivative that has been shown to be non-cariogenic in experimental animals. The purpose of this study was to determine whether certain oral bacteria could utilize sucralose. Sucralose, as a sole carbon source, was unable to support growth of ten strains of oral bacteria and dental plaque. When sucralose was incorporated into a liquid medium containing glucose or sucrose, all organisms tested displayed similar pH falls, compared with controls. The incorporation of 126 mmol/L sucralose into glucose agar medium caused total inhibition of growth of Streptococcus sobrinus 6715-17, Streptococcus sanguis 10904, Streptococcus sanguis Challis, Streptococcus salivarius, and Actinomyces viscosus WVU627. Sucralose had no effect on IPS production. Sucralose was not bound to, nor taken up by, cells.

Sucralose inhibited the formation of glucan and fructan polymers in proportion to the sucralose-to-enzyme ratio, but independent of the sucrose concentration in the assay mixture. No radioactive polymer was formed from 14C-U-sucralose added to mixtures containing glucosyltransferase (GTF) or fructosyltransferase (FTF). Inhibition of GTF and FTF by sucralose was removed following dialysis of the enzyme/sucralose mixture. These results show that sucralose was not utilized by the oral bacteria tested and that the inhibitory effect of sucralose on GTF and FTF was non-competitive and reversible. The results further support the concept that sucralose is non-cariogenic.
Effects of Diabetes and Insulin on α-amylase Messenger RNA Levels in Rat Parotid Glands
Authors: Kim S.K. , Cuzzort L.M. , McKean R.K. , Allen E.D.
Published: November 2010

Previous studies have shown that amylase levels are reduced significantly in the pancreas and parotid gland of diabetic rats and that insulin reverses this effect and increases the secretory protein levels. In the pancreas, these changes in amylase protein levels are accompanied by parallel changes in amylase mRNA levels. In the present study, the effects of diabetes and subsequent insulin treatments on contents ( per cell) of amylase protein and its mRNA in parotid glands were compared in rats rendered diabetic with an injection of a beta-cell toxin, streptozotocin (STZ). Both amylase protein and its mRNA contents were reduced significantly in diabetic rats, compared with control rats, and this reduction was reversed following insulin injections of diabetic rats. In insulin-injected diabetic rats, amylase protein contents increased before a detectable increase in amylase mRNA levels was seen. The mRNA contents of a non-secretory protein, actin, did not change during diabetogenesis or subsequent insulin treatments. The reductions in parotid contents of amylase and its mRNA in diabetic rats and the reversal of these changes by insulin are similar to those changes that occur in the pancreas under the same conditions. However, the magnitude of these changes in parotid glands was much smaller than in the pancreas, and the effect of insulin on amylase mRNA synthesis was not as immediate as in the latter gland.
Chondrocyte-like Colony Formation of Mesenchymal Cells by Dentin Extracts in Agarose Gel Culture
Authors: Harada K. , Oida S. , Sasaki S. , Enomoto S.
Published: November 2010

In this study, the effects of guanidine extracts from demineralized bovine dentin matrix on rat mesenchymal cells were investigated by use of an agarose gel culture. The dentin extracts were divided into water-soluble and -insoluble fractions. Rat mesenchymal cells obtained from the cultivation of skeletal muscle tissue and embedded in agarose gel were treated with these two fractions. After three weeks of cultivation, the treated cells formed colonies that were stained metachromatically with toluidine blue in a dose-dependent manner. The activity necessary to form chondrocyte-like colonies by the water-insoluble fraction was significantly higher than that by the water-soluble fraction. Each chromatographic fraction of the water-insoluble part of dentin extracts on tandem Sephacryl S-200 High-resolution columns was also investigated. Chondrocyte-like colony-forming activity was concentrated in a single fraction. However, the electrophoretic pattern of this fraction revealed that there were still some bands of molecular weight between 18 and 30 kDa. According to the Western blot analysis of this fraction, there was a band corresponding to purified transforming growth factor β (TGF-β) under the non-reducing condition. After reduction, this band disappeared and we found a band corresponding to a component of 13 kDa as well as TGF-β. These findings suggest that TGF-β is present not only in bone but also in the dentin matrix.
Microtrauma to Rat Superficial Masseter Muscles Following Lengthening Contractions
Authors: Hutchins M.O. , Skjonsby H.S.
Published: November 2010

Repetitive lengthening contractions have been predicted as a mechanism causing injury, pain, and delayed soreness in the hyperactive masticatory muscle. This mechanism was examined by the mechanical lengthening of the contracted superficial masseter (SM) muscle in anesthetized rats. Repetitive stimulation of the left SM to tetanic tension was followed by mechanical lengthening, which stressed contracted muscle. The contralateral muscle was passively lengthened repetitively. Contractile tension in response to a varying frequency of stimulation was measured in pre- and post-lengthened SM muscles. A selective loss of force at all frequencies up to 100 Hz occurred in the muscles subjected to lengthening contractions. Low-frequency fatigue did not occur in SM muscles passively lengthened. All animals recovered without loss of weight or dehydration. They were killed at 24 or 72 h post-lengthening. The SM muscles were collected, and no significant differences were found in mean weight, length, or cross-sectional area when the right and left SM muscles were compared at 24 or 72 h. Two observers independently examined histological sections of SM muscles and graded the localized inflammatory sites on a scale of 1-4. A non-parametric statistical test was used so that the inflammatory scale for each muscle could be ranked. There were significantly more injured sites in SM muscles subjected to lengthening contractions, compared with the lengthened (but relaxed) SM muscles. The SM muscles of anesthetized rats were internally injured by repetitive lengthening contractions, and they exhibited low-frequency fatigue. These findings support the hypothesis that repetitive lengthening contractions in the masticatory muscle could be a mechanism for the pain and dysfunction of masticatory muscles in humans with certain parafunctional habits.
Inhibition of Streptococcus mutans Adherence by Means of Surface Hydrophilization
Authors: Olsson J. , Carlén A. , Holmberg K.
Published: November 2010

Derivatives of polyalkylene oxide (PAO) were examined for their ability to inhibit adherence of 3H-labeled cells of Streptococcus mutans to hydroxyapatite (HA) and to plastic surfaces treated with buffer or parotid saliva from two individuals. Pellicles formed on HA with saliva from the two subjects were distinct in their binding capacity. One saliva promoted and the other saliva reduced adherence, as compared with the buffer control (BHA). Three of the PAO compounds effectively hindered binding of bacteria to BHA. However, on saliva-treated HA (SHA) the inhibition was not as effective. One compound, a phosphated polypropylene glycol, was potent in inhibiting adherence both to BHA and to the plastic surfaces treated with either buffer or saliva. However, treatment of HA with this compound followed by saliva incubation only gave a limited reduction in the number of bacteria binding. Evidently, salivary constituents are capable of interacting also with the PAOtreated surface. When 14C-labeled hydrophilizing agent was used, it was shown that the PAO was not replaced by salivary molecules. Instead, the components of the saliva that mediate the binding of bacteria seemed capable of adhering directly to the PAO layer.
Preliminary Surface Analysis of Etched, Bleached, and Normal Bovine Enamel
Authors: Ruse N.D. , Smith D.C. , Torneck C.D. , Titley K.C.
Published: November 2010

X-ray photoelectron spectroscopic (XPS) and secondary ion-mass spectroscopic (SIMS) analyses were performed on unground un-pumiced, unground pumiced, and ground labial enamel surfaces of young bovine incisors exposed to four different treatments: (1) immersion in 35% H2O2 for 60 min; (2) immersion in 37% H 3PO4 for 60 s; (3) immersion in 35% H2O2 for 60 min, in distilled water for two min, and in 37% H3PO 4 for 60 s; (4) immersion in 37% H3PO4 for 60 s, in distilled water for two min, and in 35% H2O2 for 60 min. Untreated unground un-pumiced, unground pumiced, and ground enamel surfaces, as well as synthetic hydroxyapatite surfaces, served as controls for intra-tooth evaluations of the effects of different treatments. The analyses indicated that exposure to 35% H2O2 alone, besides increasing the nitrogen content, produced no other significant change in the elemental composition of any of the enamel surfaces investigated. Exposure to 37% H3PO4, however, produced a marked decrease in calcium (Ca) and phosphorus (P) concentrations and an increase in carbon (C) and nitrogen (N) concentrations in unground un-pumiced specimens only, and a decrease in C concentration in ground specimens.

These results suggest that the reported decrease in the adhesive bond strength of resin to 35% H 2O2-treated enamel is not caused by a change in the elemental composition of treated enamel surfaces. They also suggest that an organic-rich layer, unaffected by acid-etching, may be present on the unground un-pumiced surface of young bovine incisors. This layer can be removed by thorough pumicing or by grinding. An awareness of its presence is important when young bovine teeth are used in a model system for evaluation of resin adhesiveness.
The Effect of Oxygen Inhibition on an Unfilled/Filled Composite System
Authors: Rueggeberg F.A. , Margeson D.H.
Published: November 2010

Oxygen is known to inhibit vinyl polymerization in resins used for restorative dentistry. This research examined the effects of unfilled resin being blown into a thin layer on etched bovine enamel in atmospheres of room air, argon, or a combination of the two. Onto this thin, cured resin surface, filled resin was added and cured under atmospheric conditions similar to those of the initial polymerization of the unfilled resin. Comparison of the effects of the different testing atmospheres was made by measurement of the shear bond strength of the resin/composite disc to the etched bovine enamel. Monomer conversion values of the unfilled resin were calculated from the infrared spectra of the simulated tooth/disc assembly. Blowing unfilled resin with compressed room air prior to curing caused poor monomer conversion values and resulted in low shear bond strength to etched enamel. Both high monomer conversion and shear strength values resulted when specimens were cured under all-argon conditions. A clinically practical method of maintenance of the tooth under a continuous stream of argon while being cured in room air was shown to provide greater monomer conversion than curing under room-air conditions alone. SEM evaluation showed that the inhibited layer present in room-air curing was both physically displaced by and absorbed into the overlying filled composite. Specimens cured in argon showed an intact, uniformly thick layer of bonding resin next to the etched enamel, with no displacement by or absorption into the composite addition. Unfilled resin cured in room air had a significantly greater thickness of polymerization-inhibited material than did resin cured in an argon atmosphere.
Gradual Increases in Marginal Leakage of Resin Composite Restorations with Thermal Stress
Authors: Momoi Y. , Iwase H. , Nakano Y. , Kohno A. , Asanuma A. , Yanagisawa K.
Published: November 2010

The effects of thermal stress on the marginal leakage of resin composite restorations in bovine teeth were investigated by a method that preserved the specimens. The changes in marginal leakage of specimens with increasing numbers of thermal cycles were measured by an electrical conductivity method. Four brands of posterior resin composites were used to fill cylindrical cavities (2.0 mm in diameter and 1.5 mm in depth) on the labial surfaces of bovine incisors, according to the manufacturer's instructions. Thermal cycling stress was applied to the specimens for up to about seven weeks (9000 cycles). During this time, the electrical conductance between the pulp and a drop of physiological saline solution covering the resin restoration was measured periodically by application of an electrical potential (60 Hz, 10 Vp-p).

Thermal stress increased the marginal leakage gradually, rather than step-wise. Even before application of any thermal stress, wide variations of marginal leakage were found among different specimens restored with the same brand of resin. Specimens with less initial leakage showed less increase in leakage, and vice versa, throughout the experimental period.
Finite Element Analysis of the Relationship between Clasp Dimensions and Flexibility
Authors: Yuasa Y. , Sato Y. , Ohkawa S. , Nagasawa T. , Tsuru H.
Published: November 2010

A parameter study with use of the finite element method was conducted for examination of the relationships between the shape parameters of a clasp (width and thickness at the base and tip of the clasp) and its displacement or stress. By synthesis of these relationships, a simple formula defining the clasp tip displacement in terms of clasp dimensions ("displacement formula") was obtained. A stiffness parameter "Fd" (the load producing a 1-mm displacement of the clasp tip) was proposed, and a formula defining Fd in terms of shape parameters was derived from the displacement formula. Fd would be a practical parameter for the definition of clasp retention, and the present formulae appear to be useful tools for investigation of the retention of removable partial dentures.
Formation of Acellular Root Cementum in to Dental and Non-dental Hard Tissues in the Rat
Authors: Beertsen W. , Everts V.
Published: November 2010

After the periodontium of the rat was wounded, the formation of acellular extrinsic fiber cementum (AEFC) did not appear to be restricted to the hard dental tissues (pre-existing cementum, dentin, and enamel). Layers resembling AEFC were also deposited along the inner wall of the alveolar bone. At the time of observation (six weeks after being wounded), cells other than fibroblast-like cells could not be distinguished close to the newly formed AEFC-like layers. We suggest that the deposition of this material was related to the activity of periodontal ligament fibroblasts.
Electromyographic Heterogeneity in the Human Temporalis Muscle
Authors: Blanksma N.G. , Van Eijden T.M.G.J.
Published: November 2010

This study examined the possible existence of regional differences in activation of the temporalis muscle. Since the muscle is fan-shaped, its fibers pull in different directions. This suggests regional specialization for different motor tasks. EMG activity was registered by six bipolar fine-wire electrodes inserted anteroposteriorly across the muscle belly. Muscle signals were recorded during different static bite tasks for which both the direction and magnitude of bite force were specified. The results showed that the ratio of activities of the six muscle regions changed with the direction of bite force. This indicates a partitioning of the excitatory command to the muscle's motoneuron pool. Alteration in activity with changing bite-force direction was generally the smallest in the anterior-most region of the muscle, the largest in the posterior-most region, and the intermediate in the interjacent regions. Generally, all muscle regions exhibited the highest EMG activity when the bite force was in an approximately posterolateral direction. The muscle was activated uniformly only for bites in this preferential direction. Activity in the regions appeared to be scaled up or down in a linear way according to the desired bite-force level. The results indicate that the direction of pull of the muscle and the maximal force it can produce are not fixed, but depend on the direction of bite force.
Bacteremia in Children Following Dental Extraction
Authors: Coulter W.A. , Coffey A. , Saunders I.D.F. , Emmerson A.M.
Published: November 2010

The incidence and intensity of bacteremia following tooth extraction in children were measured by blood culture. The effects on bacteremia of the number and type of teeth extracted, oral hygiene, gingival health, presence of abscess, and antibiotic prophylaxis were assessed. Antibiotic prophylaxis reduced the incidence of bacteremia from 63% to 35%. The intensity of bacteremia was 2 cfu/mL of blood or less in 80% of the children. An agar pour-plate method of blood culture was significantly more effective than broth in culturing the small volumes of inoculum. Of 83 bacterial strains characterized, 39 were strict anaerobes or micro-aerophilic, and the remainder mainly streptococci. S. mitior and S. sanguis were most commonly isolated, often in pure culture, and were generally sensitive to antibiotics. No direct association was demonstrated between the plaque and gingival indices and incidence of bacteremia or between the number of teeth extracted and the incidence or intensity of bacteremia. It is concluded that all children at risk from infective endocarditis require antibiotic prophylaxis prior to tooth extraction, since it is impossible for the likelihood or intensity of transient bacteremia to be clinically predicted.
Effect of Pd on the Clinical Performance of Amalgam
Authors: Mahler D.B. , Engle J.H. , Adey J.D.
Published: November 2010

The purpose of this study was to determine the effect of a small amount of Pd on the clinical performance of a high-copper spherical-particle dental amalgam. Two identical alloys, with and without 0.5% Pd, were investigated. The marginal fracture, surface texture, and surface luster of 193 clinical restorations were evaluated at one year, those of 182 at two years, and those of 144 at three years of service. In vitro corrosion tests of anodic polarization and constant potential coulometry were also conducted. Over the three-year period, the results showed no differences in marginal fracture or surface texture between the two alloys. However, the alloy with Pd showed a significant superiority in surface luster over this time period. Both corrosion tests showed less electrochemical activity on the part of the alloy containing Pd.
Preferential Adsorption of Human Neutrophil Myeloperoxidase Isoform III by Oral Bacteria
Authors: Miyasaki K.T.
Published: November 2010

Neutrophil myeloperoxidase (MPO) adsorbs to bacteria as a pre-requisite for killing by the MPO/hydrogen-peroxide/chloride system. Three chromatographically distinct isoforms of MPO (MPO I, MPO II, and MPO III) have been isolated from human neutrophils. The purpose of this study was to determine whether oral bacteria-including Actinobacillus actinomycetemcomitans, Capnocytophaga sputigena, Haemophilus aphrophilus, and Eikenella corrodens-differentially adsorb the three major isoforms of MPO from a mixture of MPO I, II, and III, and to assess the effect of pH and normal human serum (NHS) on MPO adsorption. MPO III adsorbed preferentially (i) at high bacterial concentrations, (ii) in the pH range of 6.0-8.0, and (iii) in the presence and absence of NHS. These results support the role of MPO III in the killing of oral bacteria.
The Effect of Tin on the Corrosion Behavior of the Ag-Hg Phase of Dental Amalgam and Dissolution of Mercury
Authors: Marek M.
Published: November 2010

The anodic polarization behavior of the Ag-Hg matrix phase of dental amalgam (γ1) and the rate of mercury dissolution were examined as a function of the tin content. The objectives were to determine the effect of tin on the electrochemical behavior and dissolution of mercury and to provide evidence on whether tin dissolves in the γ1 phase or precipitates as a tin-rich phase.

Anodic polarization curves were recorded for specimens of the γ1 phase containing 0-1.5% Sn and for the γ2 phase and a γ2-containing dental amalgam, in synthetic saliva. Mercury dissolved in synthetic saliva in 24 h was determined for the γ1 phase containing 0-1.0% Sn, with cold-vapor Atomic Absorption Spectrophotometry used for mercury analysis.

Tin induced passive behavior of the γ1 phase and suppressed mercury dissolution. The passive γ 1 phase did not exhibit a breakdown of passivity occurring at the γ 2 phase. The results were consistent with the tin presence in γ 1 in a solid solution, rather than in tin-rich precipitates, and indicated that at least 1.5% Sn can be dissolved in γ1 at 37°C.
Influence of Hydrophobicity on Oligopeptide Utilization by Oral Streptococci
Authors: Cowman R.A. , Baron S.S.
Published: November 2010

The growth responses of Streptococcus mutans VA-29R, Streptococcus sanguis ATCC 10556, and Streptococcus mitior NIH to hydrophilic and hydrophobic peptides obtained following isopropanol fractionation of Trypticase were compared. Although the two fractions contained peptides of similar molecular size, differences were observed with respect to amino acid compositions. S. mutans VA-29R showed a pronounced difference in growth response to hydrophilic vs. hydrophobic peptides. While growth of this micro-organism on hydrophilic peptides was indistinguishable from that on unfractionated Trypticase, only very slow growth occurred on the hydrophobic peptides. S. sanguis ATCC 10556 and S. mitior NIH also displayed some selectivity, as evidenced by their faster relative growth rates on hydrophilic, as compared with hydrophobic, peptides. The results of this study support the conclusion that the properties of the substrate, as defined by its amino acid composition, may be more important than molecular size as a factor influencing recognition and subsequent utilization of oligopeptides as sources of amino acids for growth by these three oral streptococci.
Setting Reactions and Compressive Strengths of Calcium Phosphate Cements
Authors: Fukase Y. , Eanes E.D. , Takagp S. , Chow L.C. , Brown W.E.
Published: November 2010

Setting reactions and compressive strengths of a self-hardening calcium phosphate cement (CPC) were investigated. The CPC consists of tetracalcium phosphate (TTCP) and anhydrous dicalcium phosphate (DCPA). The cement specimens were prepared by mixing 0.7 g of the powder (TTCP 72.9 wt% + DCPA 27.1 wt%) with 0.175 mL of the liquid (25 mmol/L H3PO4 and 1.32 mmol/L sodium fluoride). The specimens were removed from the molds at pre-determined time intervals after being mixed, and their compressive strengths were measured. Immediately afterward, the fractured specimens were rapidly frozen in ethanol (- 80°C), lyophilized, and examined by powder x-ray diffraction and scanning electron microscopy (SEM). The results showed that (1) hydroxyapatite was the only reaction product; (2) the reaction was nearly completed within four h, during which both the reaction product and compressive strength increased linearly with time, resulting in a strong correlation between the two; and (3) fully set CPC consisted primarily of small rod-like crystals and some platy crystals.
Video Microscope Observations of Human Premolar Eruption
Authors: Proffit W.R. , Prewitt J.R. , Baik H.S. , Lee C.F.
Published: November 2010

It is now possible to observe with an accuracy of 1-2 μm the pattern of eruptive movements of a human premolar as it moves from gingival emergence to the occlusal plane. This was accomplished by use of a video microscope to track the position of an optical ruling on the erupting tooth relative to a reference ruling mounted on adjacent teeth that were in occlusion. Net eruptive movements averaging 25-75 μm occurred from one day to the next until the tooth was almost in occlusion; then the eruptive rate slowed. Eruption occurred almost entirely at night. During the day, there was a marked slowing or cessation of eruption and often intrusion, which appeared to be related to masticatory activity.