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The tensile bond strength of Epoxylite 9075 and Enamelite to enamel treated with NaF and SnF2, at two concentrations, in the etching acid (H3PO4) was determined. The average fracture stress of those samples in which fracture occurred in the resin only, may be considered as the tensile strength of the resin, 69.8 +/- 5.6 kg/cm2. The mean fracture stresses of the Epoxy 9075 systems etched with pure phosphoric acid or with acid solutions containing 0.5% F salts were significantly higher than those treated with acid solutions containing 2% F salts. Incorporation of NaF or SnF2 in the etching solutions highly increased the fluoride concentration of enamel. The fluoride increase dependend on the fluoride concentration of the etching solution and was greater for NaF than SnF2.
OBJECTIVES: This study was conducted to evaluate enamel morphology after laser etching and acid etching and to determine the shear bond strength of composite to acid-etched and laser-treated enamel. METHODS: Enamel from freshly extracted permanent molar teeth was subjected to either laser treatment with an Nd:YAG laser in different laser parameters or was exposed to 37% phosphoric acid for 60 s (Gluma Gel, Bayer Dental). Surface profile analysis of the enamel was undertaken with a Perthometer (S8P, Feinpruif). The results were analyzed by SPSS/PC multiple range test and Student-Newman Keuls procedure. Specimens were examined in a scanning electron microscope (SEM). Shear bond strengths of acid-etched and laser-etched enamel/composite (Brilliant Dentin, Coltene AG and Pekalux, Bayer Dental) were also determined. These results were compared by SPSS/PC multiple range test. RESULTS: The acid-etched specimens exhibited a qualitatively different type of enamel surface morphology when compared with the laser-treated specimens. Laser treatment at higher exposures resulted in the formation of microcracks and fissures. No significant difference in surface roughness was observed between laser-treated enamel in three different parameters (10 pps, 0.8 W; 15 pps, 1.0 W; 20 pps, 1.25 W) and acid-etched specimens. However, the mean bond strengths of all laser-treated specimens, regardless of the test parameters, were significantly lower (p < 0.05) than the acid-etched enamel specimens. SIGNIFICANCE: Although the laser roughened the surface of the enamel, it did not provide a surface as retentive as a surface treated with conventional acid etching. It is concluded from this study that the Nd:YAG laser operated under the conditions described cannot be recommended as a viable alternative to acid etching.
The dynamics of the intermolecular short hydrogen bond in the molecular complex of urea and phosphoric acid are investigated using plane-wave density functional theory. Results indicate migration of the proton toward the center of the hydrogen bond as temperature is increased, in line with recent experimental measurements. Computed vibrational frequencies show favorable agreement with experimental measurement. An analysis of existing neutron diffraction data leads us to conclude that the effective potential well experienced by the proton is temperature-dependent. Inspired by our computations and theoretical analysis, we offer a possible explanation for the proton migration phenomenon.
The effect of N-palmitoyl-L-serine phosphoric acid (L-NASPA), which has been used as an inhibitor of lysophosphatidic acid receptors, on intracellular Ca2+ concentration ([Ca2+]i) in human osteosarcoma MG63 cells was measured by using fura-2. L-NASPA (0.1-10 microM) caused a rapid and transient plateau [Ca2+]i rise in a concentration-dependent manner (EC50=0.5 microM). The L-NASPA-induced [Ca2+]i rise was partly reduced by removal of extracellular Ca2+ but was not altered by L-type voltage-gated Ca2+ channel blockers. In Ca2+-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+-ATPase, induced a [Ca2+]i rise, after which the increasing effect of L-NASPA on [Ca2+]i was completely inhibited; also, pretreatment with L-NASPA partly reduced thapsigargin-induced [Ca2+]i rise. U73122, an inhibitor of phospholipase C, abolished histamine (but not L-NASPA)-induced [Ca2+]i rise. Overnight incubation with 1 microM L-NASPA did not affect cell proliferation, but 10-20 microM L-NASPA exerted 4% and 15% inhibition, respectively. Collectively, L-NASPA rapidly increased [Ca2+]i in MG63 cells by evoking both extracellular Ca2+ influx and intracellular Ca2+ release, and is cytotoxic at higher concentrations.
PURPOSE: The purpose of this in vitro study was to determine the shear bond strengths (SBS) of Non-Rinse Conditioner (NRC, Dentsply) combined with Prime & Bond NT (PBNT, Dentsply), a 1-bottle adhesive. The null hypothesis tested was that the use of NRC with PBNT would not result in SBS different from those obtained with conventional phosphoric acid (PA) etching and bonding application to permanent and primary dentin. METHODS: Extracted human third molars and primary molars were mounted length-wise in acrylic resin. The occlusal surfaces were ground to expose a flat dentin surface, and then polished to 600 grit silicon carbide paper to create smear layers similar to those created with high-speed burs. The teeth were randomly assigned to 4 groups (N = 10) according to the etchant/conditioner (PA vs NRC) and dentin (permanent vs primary) used: (Group I: permanent dentin, PA, PBNT; Group II: primary dentin, PA, PBNT; Group III: permanent dentin, NRC, PBNT; Group IV: primary dentin, NRC, PBNT). Specimens were then secured in a split mold, having a 5 mm diameter opening and a polyacid-modified resin composite (Dyract AP, Dentsply) were inserted and light cured incrementally onto the treated dentin surfaces. All specimens were stored in water for 24 hours prior to shear strength testing using a Franell testing machine at a crosshead speed of 0.8 mm/minute. RESULTS: The mean dentin SBS values (MPa) for the groups were: Group I (13.32 +/- 6.6); Group II (15.21 +/- 5.25); Group III (8.87 +/- 3.12); and Group IV (7.42 +/- 2.98). Analysis of variance and Duncan's multiple range tests indicated significant differences among groups at P < 0.05. CONCLUSIONS: In general, the SBS were remarkably greater in the 2 groups etched with PA in comparison with the 2 groups conditioned with NRC. However, the type of dentin tissue did not influence SBS.
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Two experiments were conducted to study the pattern of change in serum inorganic phosphorus level in laying hens fed a diet containing 0.30% total phosphorus after dosing with a known amount of phosphorus. Serum phosphorus level of undosed hens was 2.5 mg/100 ml at oviposition in both experiments. After dosing with 100 mg of phosphorus in 10 ml of a phosphoric acid solution, serum phosphorus level increased sharply and reached a peak of about 7.0 mg/100 ml between 30 and 60 minutes in experiment 2. After the peak the elevated level of serum phosphorus decreased logarithmically until 5 to 6 hours after dosing and eventually decreased to 2.5 mg/100 ml which was the serum phosphorus level of undosed hens in experiment 1. The half-life of the elevated portion of serum phosphorus due to the dosing was about 100 minutes.
In recent years there has been an increasing awareness of the radiological impact of non-nuclear industries that extract and/or process ores and minerals containing naturally occurring radioactive material (NORM). These industrial activities may result in significant radioactive contamination of (by-) products, wastes and plant installations. In this study, scale samples were collected from a decommissioned phosphoric acid processing plant. To determine the nature and concentration of NORM retained in pipe-work and associated process plant, four main areas of the site were investigated: (1) the 'Green Acid Plant', where crude acid was concentrated; (2) the green acid storage tanks; (3) the Purified White Acid (PWA) plant, where inorganic impurities were removed; and (4) the solid waste, disposed of on-site as landfill. The scale samples predominantly comprise the following: fluorides (e.g. ralstonite); calcium sulphate (e.g. gypsum); and an assemblage of mixed fluorides and phosphates (e.g. iron fluoride hydrate, calcium phosphate), respectively. The radioactive inventory is dominated by 238U and its decay chain products, and significant fractionation along the series occurs. Compared to the feedstock ore, elevated concentrations (< or =8.8 Bq/g) of 238U were found to be retained in installations where the process stream was rich in fluorides and phosphates. In addition, enriched levels (< or =11 Bq/g) of 226Ra were found in association with precipitates of calcium sulphate. Water extraction tests indicate that many of the scales and waste contain significantly soluble materials and readily release radioactivity into solution.
In order to improve or supplement the currently used therapy of poisoning with phosphoric acid esters, a protein free extract from calf blood containing low-molecular subtances (Actihaemyl, Solcseryl) has been tested in female Wistar rats. After poisoning with paraoxon, DFP and soman, a combination of Solcoseryl, Toxogonin and atropine sulfate prolonged the time until exitus, improved the overall rate of survival and considerably shortened the phase of regeneration of the experimental animals even when they had been intoxicated with high doses of poison.
The process of phosphor-gyps is associated with the pollution of the working environment by aerosols containing Ca, Fe, Si, P, fluorides, and other substances. Sanitary measures for the working environment and studies of the aerosol effects on human health are proposed.
Formation of S-carbamidomethylmethionine (camMet) occurs as a side reaction during cysteine alkylation with iodoacetamide (IAA). In collision-induced dissociation, peptides with camMet show an abundant neutral loss of 2-(methylthio)acetamide (C3H7NOS = 105.025 Da) at moderate collision offset values which are similar to those optimal for loss of phosphoric acid (H3PO4 = 97.977 Da). Neutral loss analysis is used for spotting of phosphopeptides which contain phosphoserine (pSer) or phosphothreonine (pThr) residues. In the case where precursor ions cannot be accurately assigned in the survey spectrum (e.g. due to low ion abundance or signal overlap), the mass accuracy of a neutral loss tandem mass spectrometry (MS/MS) analysis depends on the precursor ion isolation window. For the charge states 2+, 3+ or 4+, a typical 3.5 Da precursor isolation window results in neutral loss windows of 7, 10.5 or 14 Da, respectively. Consequently, neutral loss of 105 Da from alkylated methionine residues can mimic the phosphoserine/phosphothreonine-specific neutral loss of 98 Da. In the evaluation of quadrupole time-of-flight (QTOF) parent ion scan data for neutral loss of H3PO4, this interference was frequently observed. It is illustrated in this study using the analysis of ovalbumin phosphorylation as an example. The +80 Da molecular weight shift connected with phosphorylation at serine or threonine may also be mimicked by carbamidomethylation of methionine through a combination with sodium adduction (+57 Da +22 Da = +79 Da). For highly sensitive neutral loss analysis of serine and threonine phosphorylation, careful data inspection is recommended if reduction and alkylation by IAA is employed.
Reserpine-rescinnamine group alkaloids are extracted from Rauwolfia serpentina preparations into dimethylsulfoxide (DMSO)-methanol and diluted with 0.5N H2SO4. The chloroform extract of this solution is passed through a 0.1N NaOH-Celite column and then through a silica gel column. The weakly basic alkaloids trapped on the latter column are eluted with chloroform-methanol; a portion of the eluate is treated with a vanadium pentoxide-phosphoric acid solution, and the reserpine-rescinnamine content is determined by measuring the intensity of the resulting fluorescence. The following means and standard deviations (11 collaborators) were obtained for the determination of reserpine-rescinnamine group alkaloids in 4 samples of Rauwolfia serpentina (NF reference powder, 100 and 50 mg commercial tablets, and 45 mg synthetic tablet formation): 0.173%, 0.0050; 0.128%, 0.0030; 0.150%, 0.0069; and 0.142%, 0.0032; respectively. The method has been adopted as official first action.
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The uptake of tritiated N,N-bis(2-chloroethyl)-diamido-phosphoric-acid into Ehrlich-Ascites-Tumor cells of mice was studied by means of the siliconoil-filtration technique. At 10 mM concentration no permeation of the metabolite into the tumor cells could be found within 5 min at 1 degrees C, while its congenors cyclophosphamide and 4-hydroperoxycyclophosphamide (1 mM) were shown to permeate into the cells very easily reaching saturation values. Thus lack of permeation into tumor cells of N,N-bis(2-chloroethyl)-diamidophosphoric-acid seems to be the reason for the poor cytotoxic activity of this metabolite of cyclophosphamide.
In this case report, a congestive cardiomyopathy caused by long-term organic phosphoric acid ester exposure is described. The cardiotoxicity and the role of such poisons in the genesis of cardiomyopathy are also discussed.
Pyromorphite (Pb(5)(PO(4))(3)Cl) is a Pb mineral whose rapid kinetic formation and thermodynamic stability (Geochim. Cosmochim. Acta 37 (1973) 367, Geochim. Cosmochim. Acta 38 (1974) 887) has gained much attention in recent years as a mechanism to diminish Pb toxicity. Our research examined the in vitro formation of pyromorphite (K(sp) = 10(-25)) to significantly reduce Pb bioavailability via the reaction of PbCl(2) and Pb paint with cola soft drinks (regular, caffeine-free, and diet) that contain phosphoric acid. X-ray diffraction spectroscopy was employed to identify and quantify the crystal phases. The experiments consisted of a two-phase experimental design to simulate stomach and gastrointestinal (GI) conditions comprised of an initial reaction system (stomach) at pH 2.0 for 1 h at 37 degrees C and second-phase conditions (GI tract) at pH 7.0 for 5 h at 37 degrees C. The results showed that available Pb in solution was quickly transformed to pyromorphite by a precipitation mechanism. The PbCl(2) experiments observed over 90% Pb removal from solution within 30 s and nearly all (> 93-100%) of the Pb was converted to pyromorphite within 6 h. Similar results were observed in the Pb-paint system in which all of the available Pb initially available in solution was stabilized as pyromorphite within a short reaction period. While approximately 69% of the total Pb in the paint was converted to pyromorphite, there were minimal amounts of Pb in solution. It appeared that the dissolution mechanism allowing Pb in the paint to be released into the cola solution was repressed and was attributed to precipitation of pyromorphite on the surfaces of Pb-paint particles that inhibited further Pb release. The results of this research suggest that the in vivo formation of pyromorphite in children that ingest Pb-contaminated material (soil, dust, paint) with a phosphate source, such as a cola soft drink, may significantly reduce Pb bioavailability and allow passage of the pyromorphite material through the GI tract with minimal Pb absorption into the body.
The objective of this study was to determine the relationship between the consumption of phosphoric acid-containing soft drinks and hypocalcemia in postmenopausal women. A case control study was designed to include 21 cases and 64 controls, matched by age and menopausal duration with similar family income, scholarship, and daily dietary intakes. Clinical and dietetic conditions that may produce hypocalcemia were considered as exclusion criteria. Cases were defined as a serum Ca level < or = 8.8 mg/dl, and controls as a serum CA level > 8.8 mg/dl. Women in the case group had a higher consumption of phosphoric acid-containing soft drink, and showed increased serum levels of PTH and hyperphosphaturia, than those in the control group without significant differences in 1,25(OH)2D3. In the multivariate regression analysis consumption of one or more bottles per day of cola soft drinks showed association with hypocalcemia (1.28, CI 95% 1.06-1.53). The consumption of soft drinks with phosphoric acid should be considered as an independent risk factor for hypocalcemia in postmenopausal women.