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[A comparative study of root smear layer removal using different pH EDTA salts].

OBJECTIVE: To evaluate the effect of different pH EDTA salts on removing root canal smear layers. METHODS: Sixty human teeth with single root were instrumented using step-back technique, then were irrigated with several irrigating solutions including A: 0.9% saline; B: 5.25% NaOCl +3% H2O2; C: 15% EDTA (pH = 6.5); D: 15% EDTA (pH = 13); E: 15% EDTA (pH = 6.5) 25% NaOCl +3% H2O2; F: 15% EDTA (pH = 13) 25% NaOCl +3% H2O2. After the teeth were split, the root canal walls were examined with scanning electron microscopy at the coronal, middle and apical thirds for smear layer removal. RESULTS: Except A and B group, all the groups were effective on removing smear layer at the coronal, middle thirds of the root canal, group C had a stronger effect to remove smear layer than group D (P < 0.05), group E was the most effective among these groups. However, these groups were all ineffective on removing smear layer at the apical thirds of root canal. CONCLUSIONS: 15% EDTA (pH = 6.5) 25% NaOCl +3% H2O2 was the most effective irrigation on removing smear layer.

Edetic Acid↗

Effect of conditioner on bond strength of glass-ionomer adhesive to dentin/enamel with and without smear layer interposition.

The effect of a polyalkenoic acid conditioner pretreatment on the bond strength of a glass-ionomer adhesive to tooth substrates with or without smear layer was evaluated. Smear-layer covered and smear-layer free dentin and enamel surfaces were prepared from 24 extracted human molars. Resin composite was bonded to the surfaces using FujiBond LC with or without a polyalkenoic acid conditioner and subjected to microtensile bond strength (microTBS) testing. Failure modes were determined using scanning electron microscopy. For dentin, smear-layer coverage and conditioner treatment did not reveal significant differences in microTBS, which ranged from 20 to 29 MPa. For enamel, smear-layer coverage did not significantly affect microTBS, whereas, the use of conditioner significantly improved microTBS, reaching the same microTBS-values as when bonded to dentin. Regarding failure mode, most dentin specimens failed mixed adhesive cohesively. For enamel, adhesive failures mostly occurred when no conditioner was used, though mixed failures were predominant when the specimens were conditioned beforehand. Bonding of the glass ionomer adhesive to dentin can be achieved without the separate use of a polyalkenoic acid conditioner, even with the interposition of a smear layer. However, instrumented and non-instrumented enamel requires separate conditioning to provide sufficient micro-mechanical retention.

Acrylic Resins↗

Effect of smear layer thickness and pH of self-etching adhesive systems on the bond strength and gap formation to dentin.

PURPOSE: To measure the buffering capacity of self-etching adhesive systems and to evaluate the effect of smear layer thickness on the mean gap width (GW) and microtensile bond strength (microBS) to dentin of these self-etching adhesives. MATERIALS AND METHODS: Clearfil SE Bond (SE), Optibond Solo Plus Self-Etch Primer + Optibond Solo Plus (SO), Tyrian Self Priming Etchant + One Step Plus (TY) and as controls, Single Bond (SB) and ScotchBond Multi-Purpose Plus (SC) were used with Filtek Z250 Universal Restorative. The self-etching primers and 35% phosphoric acid (0.5 ml) were titrated by adding successive 0.05 ml drops of NaOH (1N). Thirty molars (n = 5) were sectioned in halves upon which thick (60-grit SiC) and thin (600-grit SiC) smear layer surfaces were produced. The adhesive application was randomized (n = 6) and a resin buildup was made. After 24 h, the resin-dentin sticks (0.8 mm2) were prepared. The GW on the sticks was measured at 400X magnification before the microtensile test (0.5 mm/min). The microtensile bond strength index was calculated including the relative failure type contribution. Data were analyzed by a two-way ANOVA and Tukey's multiple comparison. Simple linear regression was performed to determine whether correlation existed between microBS and pH, GW and pH, and microBS and GW. RESULTS: Only the factor "adhesive" significantly effected microBS (p = 0.001). TY had the lowest microBS values. Regarding GW, both main factors adhesive (p = 0.0001) and smear layer thickness (p = 0.03) were significant. The highest mean gap width was observed for SE and under a thick smear layer. A linear relationship was observed between the pH and GW and pH and microBS; however, a significant positive correlation was detected only between pH and GW (R = 0.99, p = 0.02). No relationship between microBS and GW was found (R = 0.04, p = 0.77). CONCLUSION: Although the smear layer thickness had no effect on resin-dentin bond strength, thick smear layers adversely affected the mean gap width. The microBS values were not affected by the acidity of self-etching primers; however, more aggressive self-etching primers showed the lowest mean gap width. The etch-and-rinse adhesive systems showed higher microBS and lower mean gap widths.

Acid Etching, Dental↗

Characterization of the accessory layer of the cuticle of muscle larvae of Trichinella spiralis.

The accessory layer of the cuticle of infective larvae of Trichinella spiralis has been studied with electron microscopy using cytochemical techniques and chemical extractions. The accessory layer lacks negative charges and carbohydrates demonstrable in vivo. Staining with ruthenium red and tannic acid is interpreted as being consistent with their reactions with phospholipids. Freeze fractures demonstrate an external layer of granules that can be partially released by means of detergents (CTAB and SDS). The granules are considered to be proteins. Their removal makes the worms acid sensitive and prevents them from infecting mice. Extraction of whole worms with ethanol, acetone and methanol (via reaction with 2,2-DMP), or chloroform and methanol destroys an internal layer of filaments. Thin-layer chromatography of chloroform/methanol extracts showed principally ethanolamine phospholipids from the surface of the worms. A model is presented for the molecular organization of the accessory layer. Ethanolamine phospholipids are suggested to occur as tubular micelles. Proteins may attach to these by lipophilic moieties and perhaps by a cryptic sugar group (demonstrated by others) that may penetrate into the hydrophilic core of the lipid micelles.

Animals↗

A compositional based model for the tear film lipid layer.

BACKGROUND: The tear film lipid layer is formed from lipids secreted by meibomian glands of the eyelid. After initial analyses of these lipids we concluded that an understanding of the function of the various classes of lipids in a normal lipid layer could only be understood after detailed investigations of both polar and nonpolar lipids of the meibomian gland. METHODS: Meibomian gland secretions were obtained from normals. Lipids were separated by thin layer chromatography and high pressure liquid chromatography, and analyzed by UV absorbance, gas chromatography and mass spectroscopy. RESULTS: Based on our analyses we concluded that the current understanding of lipid layer composition and function were inadequate or misleading. We therefore propose that the more polar lipids function as a structure (with surfactant characteristics) upon which the functional stability of the more nonpolar lipids are dependent. We further suggest that the interrelationships between lipid classes present, length of fatty acids and alcohols, their unsaturation, and hydroxylation are important for maintaining proper thixotropic characteristics of the lipid layer as well as optimal barrier properties. CONCLUSION: The tear film lipid layer is composed of 2 phases: (1) a thin polar phase adjacent to the aqueous-mucin phase and (2) a thick nonpolar phase associated with both the polar phase and the air interface. The structural characteristics of the polar phase and the barrier functions of the nonpolar phase are a direct result of specific compositional parameters.

Chromatography, Gas↗

The fate of fresh, layered, nonsutured and sutured, autogenous cartilage in the rabbit model.

OBJECTIVE: To compare the thickness, area, and volume of sutured and nonsutured multilayered cartilage grafts in a rabbit population. DESIGN: Autogenous rabbit cartilage grafts were harvested, layered, and placed in the contralateral auricle. Half the grafts were sutured; the other half were nonsutured. Graft thickness, area, and volume were measured before implantation, after 90 days in vivo, and after explantation. RESULTS: The area and volume of the cartilage grafts increased during the 90-day period. Histologically, this was caused by increased fibrous tissue around the cartilage grafts. Minimal cartilage resorption was observed. No differences were noted between sutured and nonsutured grafts. CONCLUSIONS: Autogenous, fresh, uncrushed, layered nonsutured or sutured cartilage grafts are well tolerated. Statistically significant increases in the area and volume of autogenous, fresh, uncrushed, layered cartilage grafts occurred primarily because of fibrous tissue formation at the margins of the layered grafts. Suturing had no effect on the postoperative volume retention of these layered grafts. This information will be helpful to the facial plastic surgeon when using fresh-layered autogenous cartilage grafts during cosmetic or reconstructive procedures. Arch Facial Plast Surg. 2000;2:256-259

Animals↗

Posterior collagenous layer of the cornea. Ultrastructural classification of abnormal collagenous tissue posterior to Descemet's membrane in 30 cases.

We studied the transmission electron microscopy of the abnormal collagenous tissue posterior to Descemet's membrane in 30 human corneas that represented 19 different diseases. We named this abnormal tissue the "posterior collagenous layer" of the cornea and classified it into three morphologic types: (1) banded posterior collagenous layer, characterized by 110-nm wide-spacing material, (2) fibrillar posterior collagenous layer, characterized by loose meshwork of collagenous fibrils 20 to 30 nm in diameter, and (3) fibrocellular posterior collagenous layer, characterized by fibroblasts in connective tissue. The published ultrastructural studies of 88 corneas that represented 13 different clinical disorders fit this classification well. The posterior collagenous layers often formed multiple lamellae, but no pattern was invariably associated with a specific clinical disorder. We think these multiple layers represent successive periods of deposition of collagen by a stressed corneal endothelium and provide a lifelong record of senescent and pathologic events.

Adolescent↗

Atypical nerve fiber layer defects in high myopes with high-tension glaucoma.

The incidence of atypical optic nerve head and retinal nerve fiber layer defects was studied in 61 high myopic eyes (greater than or equal to -5 diopters) and 91 emmetropic or hyperopic eyes (0 to +3 diopters) of 152 patients with chronic high-tension glaucoma, and in 45 control myopic eyes (greater than or equal to -5 diopters). Horizontal ovalness or cyclotorsion, oblique insertion of the optic disc, and bean pot disc were more common in the high myopes. In the eyes with high myopia with glaucoma, inferior dominant nerve fiber layer defects, ectopic fiber defects, and multiple nerve fiber layer defects were common. The incidence of superior nerve fiber layer defects or superior-inferior equal nerve fiber layer defects was high in round or vertically oval discs and low in cyclotorted or horizontal oval discs. The oblique insertion of the discs correlated positively with a higher incidence of ectopic defects in high myopic eyes with glaucoma. The incidence of focal type nerve defects is higher in older patients and high myopes with oblique insertion of the optic disc. Atypical shape of the optic disc correlates positively with atypical retinal nerve fiber layer defects in eyes with high-tension glaucoma.

Adolescent↗

Esophagojejunostomy with manual single layer suturing after a total gastrectomy for gastric cancer.

BACKGROUND: We wished to verify the clinical usefulness of manually performed single layer suturing for an esophagojejunostomy after a total gastrectomy versus stapled suturing. METHODS: We compared retrospectively 24 patients who underwent manual single layer suturing with 38 patients who underwent stapled suturing. RESULTS: Anastomotic leakage was seen in one patient (4%) with single layer suturing and one patient (3%) with stapled suturing. No anastomotic stenosis was seen in the patients with single layer suturing. There was no difference in the operative time, blood loss, postoperative days for oral intake, or the length of hospital stay between the patients with single layer suturing and those with stapled suturing. CONCLUSIONS: Manual single layer suturing is considered to be as safe as stapled suturing and is also thought to be clinically useful in reducing anastomotic failure for esophagojejunostomy.

Adult↗

Spatiotemporal pattern of ontogenetic expression of calbindin-28/kD in the retinorecipient layers of rat superior colliculus.

Using an antibody against calbindin-28kD, we have studied the spatial pattern of expression of this protein in the superior colliculi (SC) of four strains of mature laboratory rats. In all four strains, calbindin-expressing cells (CECs) formed horizontally oriented tiers in the retinorecipient and intermediate gray layers but were diffusely distributed throughout the deep layers. Ontogenetically, calbindin-28kD was expressed for the first time in the retinorecipient layers at postconceptional day 20 (PCD 20), by cells located in the rostrolateral region where the first born retinal ganglion cells (RGCs) are represented. Although on the day of birth (PCD 22/23), the CECs were distributed more widely, they were still absent in the most medial part of the SC, that is, the region where the latest born RGCs are represented. The spatial distribution of CECs became adultlike only by PCD 29, that is, at the end of the period of the naturally occurring death of the RGCs. Monocular eye enucleations on PCD 23 prevented the expression of calbindin in the medial fifth of the retinorecipient layers of the contralateral SC, while the unilateral removal of the visual cortices had no discernable effect on the numbers and distribution of the CECs in either SC. Thus, the spatiotemporal pattern of ontogenetic expression of calbindin-28kD in the retinorecipient layers of SC reflects the spatiotemporal pattern of generation of the RGCs, and the retinal input appears to induce neuronal expression of calbindin-28kD in these layers.

Animals↗

Spatial distribution of [14C]2-deoxyglucose uptake in the glomerular layer of the rat olfactory bulb following early odor preference learning.

Previous work has shown that odors induce focal uptake of [14C]2-deoxyglucose (2-DG) within the glomerular layer of the main olfactory bulb and that the amount of 2-DG accumulated in these foci increases after early odor learning. To determine if learning-associated changes in 2-DG uptake occur across the entire glomerular layer, we have mapped uptake throughout the layer at fixed angles in coronal sections through the bulb. Resulting arrays for individual bulbs were corrected for differing bulb size and averaged across experimental groups to address the spatial distribution of uptake. The average arrays revealed at least three discrete fields of uptake in naive, peppermint-exposed rats at postnatal day 19 that were not seen in air-exposed littermates. In agreement with previous studies, early preference training with peppermint odor given on postnatal days 1-18 increased 2-DG uptake at postnatal day 19 within odor-dependent patches of uptake in the posterior half of the midlateral bulb, whereas odor-dependent, ventrolateral patches of uptake did not increase to the same extent. In addition, early preference learning was associated with significantly increased 2-DG uptake average over the entire analyzed glomerular layer. These increases were smaller than those within odor-dependent foci and were distributed widely across the glomerular layer, showing low overlap between trained and control rats in anterior regions where peppermint odor did not stimulate 2-DG uptake. The widely distributed increases in 2-DG uptake after learning may reflect changed activity of centrifugal projections that diffusely innervate the glomerular layer.

Animals↗

Spatial coding of odorant features in the glomerular layer of the rat olfactory bulb.

In order to determine whether molecular features of odorants are represented spatially in the glomerular layer of the olfactory bulb, we used metabolic mapping of [14C] 2-deoxyglucose uptake in rats exposed to equal vapor concentrations of odorants differing systematically in chemical structure. The odorants were ethyl acetate, ethyl butyrate, isoamyl acetate, and isoamyl butyrate. Statistical analysis of anatomically standardized arrays of uptake revealed that each ester produced a characteristic spatial pattern of activity in the glomerular layer. The patterns were similar in different rats exposed to the same odorant, and their complexity increased with increasing odorant carbon number. This finding suggests that the presence of more potentially recognized molecular features is associated with a greater number of activated receptors. Individual regions of the glomerular layer responded specifically to isoamyl esters, and other regions preferred ethyl esters. Regions of similar specificity occurred in lateral and medial aspects of the bulb, the medial representation being more caudal and ventral than the lateral one. This pattern correlates with projections of olfactory sensory neurons expressing the same putative olfactory receptor gene. The patterns overlapped greatly in the posterolateral and posteromedial glomerular layer, a finding one should predict, given the large overlap in chemical structure across the aliphatic esters. Thus, molecular features appear to be encoded spatially in the glomerular layer, and the identity of the odorant may be determined by a subsequent decoding of the combination of molecular features represented in the glomerular layer.

Acetates↗

Development of a capacitive immunosensor: a comparison of monoclonal and polyclonal capture antibodies as the primary layer.

There is widespread interest in capacitance immunosensor systems which directly detect antigen binding to immobilized antibody. Our system comprises an active biolayer of antibodies bound to a silicon--silicon dioxide--silicon nitride (Si-SiO2-Si3N4) surface. As with other groups, our system initially gave poorly reproducible responses on addition of antigen. We mechanically degraded the Si-SiO2-Si3N4 surface, and the responses on addition of transferrin were monitored. The mechanical degradation allowed the affinity reaction to be 'seen' capacitively. Once the system was established, a comparison of capture antibodies was performed to establish the most effective biolayer. Three affinity reactions were examined: (a) 1D2A4, monoclonal antibody (mAb) to human transferrin, as the capture layer; (b) polyclonal goat anti-human transferrin antibody (PcAb) as the capture layer; and (c) 1D2A4 with transferrin (Tf) prebound as the capture layer. There was no response to addition of transferrin where 1D2A4 was the capture layer. Addition of transferrin when the polyclonal antibody was used as the primary layer resulted in a drop in measured capacitance. Addition of goat anti-human transferrin antibody to a device with 1D2A4 plus transferrin as the capture layer also resulted in a measured capacitance decrease. There is a difference in dielectric/blocking effectiveness between the monoclonal and polyclonal antibodies.

Animals↗

Integration of Layered Redox Proteins and Conductive Supports for Bioelectronic Applications.

Integration of redox enzymes with an electrode support and formation of an electrical contact between the biocatalysts and the electrode is the fundamental subject of bioelectronics and optobioelectronics. This review addresses the recent advances and the scientific progress in electrically contacted, layered enzyme electrodes, and discusses the future applications of the systems in various bioelectronic devices, for example, amperometric biosensors, sensoric arrays, logic gates, and optical memories. This review presents the methods for the immobilization of redox enzymes on electrodes and discusses the covalent linkage of proteins, the use of supramolecular affinity complexes, and the reconstitution of apo-redox enzymes for the nanoengineering of electrodes with protein monolayers of electrodes with protein monolayers and multilayers. Electrical contact in the layered enzyme electrode is achieved by the application of diffusional electron mediators, such as ferrocene derivatives, ferricyanide, quinones, and bipyridinium salts. Covalent tethering of electron relay units to layered enzyme electrodes, the cross-linking of affinity complexes formed between redox proteins and electrodes functionalized with relay-cofactor units, or surface reconstitution of apo-enzymes on relay-cofactor-functionalized electrodes yield bioelectrocatalytic electrodes. The application of the functionalized electrodes as biosensor devices is addressed and further application of electrically "wired" enzymes as catalytic interfaces in biofuel cells is discussed. The organization of sensor arrays, self-calibrated biosensors, or gated bioelectronic devices requires the microstructuring of biomaterials on solid supports in the form of ordered micro-patterns. For example, light-sensitive layers composed of azides, benzophenone, or diazine derivatives associated with solid supports can be irradiated through masks to enable the patterned covalent linkage of biomaterials to surfaces. Alternatively, patterning of biomaterials can be accomplished by noncovalent interactions (such as in affinity complexes between avidin and a photolabeled biotin, or between an antibody and a photoisomerizable antigen layer) to provide a means of organizing protein microstructures on surfaces. The organization of patterned hydrophilic/hydrophobic domains on surfaces, by using photolithography, stamping, or micromachining methods, allows the selective patterning of surfaces by hydrophobic, noncovalent interactions. Photoactivated layered enzyme electrodes act as light-switchable optobioelectronic systems for the amperometric transduction of recorded photonic information. These systems can act as optical memories, biomolecular amplifiers, or logic gates. The photoswitchable enzyme electrodes are generated by the tethering of photoisomerizable groups to the protein, the reconstitution of apo-enzymes with semisynthetic photoisomerizable cofactor units, or the coupling of photoisomerizable electron relay units.

Journal Article↗

Bioactive macroporous titanium surface layer on titanium substrate.

A macroporous titanium surface layer is often formed on titanium and titanium alloy implants for morphological fixation of the implants to bone via bony ingrowth into the porous structure. The surface of titanium metal was recently shown to become highly bioactive by being subjected to 5.0 M-NaOH treatment at 60 degrees C for 24 h and subsequent heat treatment at 600 degrees C for 1 h. In the present study, the NaOH and heat treatments were applied to a macroporous titanium surface layer formed on titanium substrate by a plasma spraying method. The NaOH and heat treatments produced an uniform amorphous sodium titanate layer on the surface of the porous titanium. The sodium titanate induced a bonelike apatite formation in simulated body fluid at an early soaking period, whereby the apatite layer grew uniformly along the surface and cross-sectional macrotextures of the porous titanium. This indicates that the NaOH and heat treatments lead to a bioactive macroporous titanium surface layer on titanium substrate. Such a bioactive macroporous layer on an implant is expected not only to enhance bony ingrowth into the porous structure, but also to provide a chemical integration with bone via apatite formation on its surface in the body.

Apatites↗

Effect of 'unstirred' water layer in the intestine on the rate and extent of absorption after oral administration.

The presence of an aqueous diffusion layer or 'unstirred' water layer adjacent to the intestinal membrane has long been regarded as a potential barrier for intestinal absorption of compounds. Theoretical analyses were performed in the present study to quantitatively determine the effect of this layer on the rate and extent of absorption of passively absorbed compounds with different membrane absorption half-lives (10 to 300 min) in humans, dogs, rabbits, rats and mice. Diffusion half-lives across this (40 microns thick) layer were estimated to be 5.8, 2.5, 1.1, 0.65 and 0.32 min, respectively, in the distended intestine of the above five species. These half-lives are reduced by about 5-fold when the intestine is about 80% 'flat' in fasting state. The results of extensive analysis indicate that the presence of such a layer is generally expected to have a relatively mild or insignificant effect on the rate of absorption and an insignificant effect on the extent of absorption. The study also indicates that an aqueous layer of 708 microns has practically no effect on the extent of absorption of progesterone, a highly lipophilic compound, in rats. For prediction of or correlation with the fraction of oral dose absorbed after oral administration, the present study indicates that use of apparent or effective permeability rather than unbiased or true wall (membrane) permeability, as advocated earlier by others, should generally suffice.

Administration, Oral↗

Randomized clinical trial and economic analysis of four-layer compression bandaging for venous ulcers.

BACKGROUND: The aim of this study was to compare the cost-effectiveness of four-layer compression bandaging for venous leg ulcers with that of other available treatments. METHODS: In this pragmatic trial, 200 patients with a venous leg ulcer were randomized either to four-layer bandaging (intervention group; n = 100) or to continue their usual system of care (control group; n = 100). The follow-up for each patient was 12 weeks. Analysis was by intention to treat; the main outcome measures were time to healing and cost to the health board per leg healed. RESULTS: Baseline characteristics were well matched in the two groups. The Kaplan-Meier estimate of the healing rate at 3 months was 54 per cent with four-layer bandaging and 34 per cent in the control group. Throughout the 3 months, four-layer bandaging healed leg ulcers significantly earlier (P = 0.006). There was a significant reduction in the median cost per leg healed with four-layer bandaging (euro 210 versus euro 234; P = 0.040). CONCLUSION: Four-layer bandaging is currently the most effective method of treating venous leg ulcers in a community setting.

Aged↗

A dual-electrode approach for highly selective detection of glucose based on diffusion layer theory: experiments and simulation.

A dual-electrode configuration for the highly selective detection of glucose in the diffusion layer of the substrate electrode is presented. In this approach, a glassy carbon electrode (GCE, substrate) modified with a conductive layer of glucose oxidase/Nafion/graphite (GNG) was used to create an interference-free region in its diffusion layer by electrochemical depletion of interfering electroactive species. A Pt microelectrode (tip, 5 microm in radius) was located in the diffusion layer of the GNG-modified GCE (GNG-G) with the help of scanning electrochemical microscopy. Consequently, the tip of the electrode could sense glucose selectively by detecting the amount of hydrogen peroxide (H2O2) formed from the oxidization of glucose on the glucose oxidase layer. The influences of parameters, including tip-substrate distance, substrate potential, and electrolyzing time, on the interference-removing efficiency of this dual-electrode approach have been investigated systematically. When the electrolyzing time was 30 s, the tip-substrate distance was 1.8 a (9.0 microm) (where a is the radius of the tip electrode), the potentials of the tip and substrate electrodes were 0.7 V and 0.4 V, respectively, and a mixture of ascorbic acid (0.3 mM), uric acid (0.3 mM), and 4-acetaminophen (0.3 mM) had no influence on the glucose detection. In addition, the current-time responses of the tip electrode at different tip-substrate distances in a solution containing interfering species were numerically simulated. The results from the simulation are in good agreement with the experimental data. This research provides a concept of detection in the diffusion layer of a substrate electrode, as an interference-free region, for developing novel microelectrochemical devices.

Carbon↗