UV Feulgen staining after hydrolysis in sulphuric and phosphoric acids at different concentrations and temperatures.
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Animals↗
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How phonons govern the behavior of short, strong hydrogen bonds in urea-phosphoric acid.
Recent neutron diffraction data have shown that the hydrogen atom involved in the short, strong hydrogen bond in urea-phosphoric acid migrates toward the midpoint of the hydrogen bond as the temperature increases. With the help of solid state ab initio calculations and inelastic neutron scattering, we have investigated the temperature dependence of the structural and vibrational properties of the system. The potential energy surface of the proton in the short, strong hydrogen bond and the thermal population of the energy levels therein cannot account for the observed proton migration. Ab initio molecular dynamics simulations clearly reveal the migration of the proton. This molecular dynamics result was reported recently by other authors, but they only offered a tentative explanation in terms of a resonance between high-frequency vibrations, which is not supported by the calculations presented here. We explain the proton migration in terms of phonon-driven structural fluctuations and their impact on the temperature-dependent evolution of the potential energy surface of the short hydrogen-bond proton.
Hydrogen Bonding↗
[Experimental substantiation of maximum allowable concentration of phosphoric acid in the water of reservoirs].
It has been found out on the basis of experimental studies, that the threshold concentration of phosphorous acid is 85.7 mg/l according to the influence on organoleptic water properties, I mg/l--according to the influence on the sanitary regimen of water reservoirs. The preparation is of low toxicity when administered perorally to laboratory animals, cumulation degree is medium. Embryotoxic and gonadotoxic effects, mutagenic and allergic properties have not been detected. The maximum no-effect dose in the chronic experiment is 1.4 mg/kg. MAC is recommended on the level of I mg/l according to the general sanitary indicator of harmfulness (the 3-d class of danger).
Animals↗
Some aromatic hydrazone derivatives as inhibitors for the corrosion of C-steel in phosphoric acid solution.
The effect of furfural benzoylhydrazone and its derivatives (I-VII) as corrosion inhibitors for C-steel in 1M phosphoric acid solution has been studied by weight-loss and galvanostatic polarization techniques. A significant decrease in the corrosion rate of C-steel was observed in the presence of the investigated inhibitors. This study revealed that, the inhibition efficiency increases with increasing the inhibitor concentration, and the addition of iodide ions enhances it to a considerable extent. The effect of temperature on the inhibition efficiency of these compounds was studied using weight-loss method. Activation energy (E(a)*) and other thermodynamic parameters for the corrosion process were calculated and discussed. The galvanostatic polarization data indicated that, the inhibitors were of mixed-type, but the cathode is more polarized than the anode. The adsorption of these compounds on C-steel surface has been found to obey Frumkin's adsorption isotherm. The mechanism of inhibition was discussed in the light of the chemical structure of the undertaken inhibitors.
Adsorption↗
Consumption of soft drinks with phosphoric acid as a risk factor for the development of hypocalcemia in children: a case-control study.
A comparison of 57 cases (in children with serum calcium concentration < 2.2 mmol/L) and 171 controls (in children with serum calcium level > or = 2.2 mmol/L) was carried out to assess whether the intake of at least 1.5 L/wk of soft drinks containing phosphoric acid is a risk factor for the development of hypocalcemia. A significant association was found: odds ratio = 5.27; 95% confidence interval, 3.17 to 8.75; p < 0.001. The hypothesis of a causal relationship between intake of phosphoric acid-containing soft drinks and hypocalcemia warrants further investigation.
Carbonated Beverages↗
Pulpal response to the application of phosphoric acid to dentin.
Experimental cavities were prepared in forty-six clinically intact premolars of young individuals to evaluate the biologic effects of 50 per cent phosphoric acid etchant containing 7 percent zinc oxide by weight. The experimental periods ranged from 30 minutes to 150 days. The remaining dentin thickness varied from 1.8 to 3.5 mm. The teeth treated with the acid showed no more than a moderate pulpal response at the varying time periods. All of the acid-treated teeth demonstrated pulpal imflammation in the absence of clinical pain. Acid etchants should not be used on exposed or unprotected dentin surfaces.
Acid Etching, Dental↗
[PHOSPHORIC ACIDS AND PHOSPHONIC ACIDS: ANALOGIES AND DIFFERENCES IN THEIR BEHAVIOR].
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Chemistry, Pharmaceutical↗
Effects of phosphoric acid concentration and etch duration on the shear bond strength of an orthodontic bonding resin to enamel. An in vitro study.
The purpose of this in vitro study was to determine the effects of phosphoric acid (H3PO4) concentration and duration of etching on the shear bond strength of an orthodontic bonding resin to enamel. Nine bonding procedures, each involving 18 extracted human maxillary permanent canines, were used. Ground enamel surfaces were etched with a 37% H3PO4 solution, a 15% H3PO4 gel, or a 5% H3PO4 solution for 60, 30, and 15 seconds, respectively. Cylinders of an orthodontic bonding resin, Concise, were prepared in a special device. The test specimens were disassembled 15 minutes after preparation and stored in distilled water at 37 degrees C for 24 hours. A shear load was applied to the bonded cylinders at a crosshead speed of 0.02 in.min-1 in an Instron testing machine, and the shear bond strengths were calculated and expressed in MN.m-2. A two-factor analysis of the data showed that the H3PO4 concentration had no significant effect on the shear bond strength, but the duration of etching affected shear bond strength significantly. The enamel aspects of the fractured test specimens were examined microscopically and the percent failure within the bonding resin at the bonding sites estimated. The correlation between shear bond strength and percentage failure within the bonding resin was not significant. The effects of the nine etching procedures on ground and unground enamel surfaces were studied by scanning electron microscopy. The etching procedures produced well-defined etching patterns on both ground and unground enamel surfaces.
Acid Etching, Dental↗
The effects of different phosphoric acid concentrations on surface enamel.
The purpose of this study was to evaluate the effects of different acid concentrations on the enamel surface morphology. The buccal surfaces of 25 extracted premolars from young patients were etched with 40%, 20%, 10%, 5%, and 2% phosphoric acid solutions for 60 seconds. The specimens were examined with a scanning electron microscope in the occlusal, central, and cervical regions. A great variation of the etching patterns was observed in almost all test groups. The extent of the appearance of prism outlines was smaller in the cervical region and at lower acid concentrations. The advantages and disadvantages of the use of lower concentrated acids are discussed.
Acid Etching, Dental↗
A method for bonding to tooth structure using phosphoric acid as a dentin-enamel conditioner.
In clinical practice it is difficult to keep acid etchants off the dentinal surface during bonding procedures. If the acid etchant could be used as part of the overall conditioning system, technique sensitivity would be reduced. This paper reports the data obtained with the use of phosphoric acid as a dentin-enamel conditioner in a bonding system developed by the author. In vitro bond strength and microleakage were examined using Dual Cure Scotchbond as a control. In both tests, the experimental group showed statistically significantly better results than did the control. A clinical study of 140 Class II restorations showed no postoperative sensitivity, and all teeth were vital after 18 months.
Acid Etching, Dental↗
Simple preparation of 1,2-dipalmitoyl-sn-glycero-3-phosphoric acid and deuterated choline derivatives.
Analytically pure 1,2-dipalmitoyl-sn-glycero-3-phosphoric acid was prepared in gram amounts, using a simplified version of a previous procedure. The main step, enzymatic cleavage of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine with freshly extracted phospholipase D, was performed in the presence of chloroform and the crude phosphatidic acid was purified by silica gel column chromatography. The interest of the method was illustrated by the synthesis of two dipalmitoyl phosphatidylcholines selectively deuterated on the polar headgroup.
Deuterium↗
Compression, compaction, and disintegration properties of low crystallinity celluloses produced using different agitation rates during their regeneration from phosphoric acid solutions.
The tabletting characteristics of low crystallinity celluloses (LCPC)-LCPC-700, LCPC-2000, and LCPC-4000-prepared using agitation rates of 700, 2000, and 4000 rpm, respectively, during their regeneration from phosphoric acid, were evaluated and compared with those of Avicel PH-102 and Avicel PH-302. The mean deformation pressure values calculated from the linear region of the Athy-Heckel curves indicated LCPC-4000 to be the most ductile material. The area under the Athy-Heckel curve for LCPC-4000 was 330 MPa, whereas LCPC-700 and LCPC-2000 showed a corresponding value similar to that of Avicel PH-102 and Avicel PH-302 (192-232 MPa). The tensile strength of LCPC and Avicel compacts increased linearly with increasing applied pressures. A comparison of the area under the tensile strength-compression pressure curves indicated that LCPC-4000 formed the strongest tablets. The strengths of LCPC-700 and LCPC-2000 compacts, in contrast, were slightly lower than that of Avicel PH-302 and Avicel PH-102, respectively. The compacts of both LCPC-4000 and Avicel PH-102 were intact in water for 6 hours, whereas LCPC-2000 and Avicel PH-302 compacts disintegrated in 4 minutes and 2 minutes, respectively. In conclusion, LCPC-4000 was the most ductile material and exhibited the highest compression and compaction characteristics. The corresponding properties of LCPC-700 and LCPC-2000, in contrast, were comparable to that of Avicel PH-102 or Avicel PH-302.
Cellulose↗
The effects of phosphoric acid, sodium hypochlorite, ferric oxalate and Scotchbond Multipurpose on the rate of pressure change across dentine: a laboratory study.
The aim of this study was to investigate the consequences of dentine treatment on dentine permeability of crown preparations treated with phosphoric acid, sodium hypochlorite (NaOCl), and then ferric oxalate (Sensodyne sealant) or bis-phenol-A-diglycidyldimethacrylate (BIS-GMA) and hydroxyethylmethacrylate (HEMA) resin combination (Scotchbond Multipurpose). Thirty human premolars received full crown preparations (stage A), were then acid etched (stage B) and subsequently the pulp chamber flushed with NaOCl (stage C). They were then randomly assigned to two groups: group 1 was treated with Scotchbond Multipurpose and group 2 with 6% ferric oxalate (Sensodyne sealant) (stage D). Both groups were acid etched a second time (stage E) as the final step in the sequence. The rise in pressure in the pulp chamber because of the transmission of saline from the pressure chamber through cut dentine was recorded by a pressure transducer after each of the stages described (A to E). The mean rate of pressure change across dentine (Pa s(-1)) for each measurement point (A to E) (n = 30) were A = 2.3; B = 9.8; C = 16; D = 2.1; E = 3.1. Acid etching and NaOCl were both effective in producing significant increases in the rate of pressure change across dentine (P < 0.05). Sensodyne sealant and Scotchbond Multipurpose are both effective dentine sealants and there is no significant difference (P > 0.05) in their abilities in sealing dentine. Acid etching-sealed dentine produced a significant increase in the rate of pressure change across dentine (P < 0.05). The sealing of dentine appears to be a sensible consideration following crown preparations on vital teeth.
Acid Etching, Dental↗
Effects of phosphoric acid concentration and etch duration on enamel depth of etch: an in vitro study.
In a previous study we reported no significant differences among the shear bond strengths resulting from the application of an orthodontic bonding resin to enamel surfaces etched with three phosphoric acid (H3PO4) concentrations, each for three etch durations. The objective of the current study was to determine the depths of etch on ground enamel surfaces exposed to the nine etching procedures. The facial surfaces of 45 extracted human maxillary permanent central incisors were ground wet on 600-grit silicon carbide paper. Annular adhesive disks of 6 mm outer diameter and 3 mm inner diameter were positioned on the ground enamel surfaces and etched with 10 mm3 of 37%, 15%, and 5% H3PO4 for 60, 30, and 15 seconds, respectively. The calcium concentrations of the etching solutions were determined and the depths of etch calculated. The depths of etch were then measured with a surface profilometer. A stepwise decrease in the calculated depths of etch with decreasing acid concentration and duration of etching was obtained. The calculated etch depths ranged from 27.1 microns by etching with 37% H3PO4 for 60 seconds to 3.5 microns by etching with 5% H3PO4 for 15 seconds. The measured depths of etch followed a similar pattern. A highly significant correlation between calculated and measured depths of etch was obtained.
Acid Etching, Dental↗
Fine incremental lines observed on the enamel surfaces with a prismless structure in human teeth after phosphoric acid etching.
In human tooth enamel, the surface prismless layer contains liner laminas homologous to the cross-striations of enamel prisms other than the Retzius lines, while these lines terminate on the perikymata or run in parallel with the enamel surface. In our present scanning electron microscope observations after phosphoric acid etching, many fine incremental lines (FIL) running transversely were found on the inner occlusal enamel with a prismless structure in a young permanent premolar. Almost the same structures were also found on the upper-coronal enamel with scattered prismless and indistinct prism structures in an exfoliated deciduous molar, and the FIL occasionally went across the indistinct prisms or caused the lower half of the prisms to disappear. Their intervals ranged from about 0.5 to 2 microns; less than the diameter of the prisms. Such results suggest that the FIL are not the termination of the laminate striations in the surface prismless layer, but that the previously unnoticed patterns sometimes formed by the sequential completion of the activity of ameloblasts which interact with each other in a transverse row at the final stage of matrix formation.
Acid Etching, Dental↗
Effect of copper salts added to primer on bonding of MMA-TBB resin to dentin treated with phosphoric acid.
The effects of addition of various copper salts to 2-hydroxyethyl methacrylate (HEMA) primer were studied with regard to tensile bond strength of methyl methacrylate-tributylborane (MMA-TBB) resin to dentin. Bovine dentin surfaces were treated with 10% phosphoric acid, then with a primer consisting of aqueous 35% HEMA and a copper salt, and finally bonded to acrylic rods with MMA-TBB resin. The types of copper salts and concentrations in the primers were varied. The optimal concentration of copper salts in the primers was 0.5-3 mumol/g. The primers containing copper salts of sulfate, methacrylate, methacryloyloxyethyl phthalate, or methacryloyloxyethyl succinate were especially effective among the eight copper salts studied in increasing bond strength, producing mean bond strengths of 14.2-16.1 MPa and mean minimum values of 9.9-11.7 MPa. These bond strengths were higher than those obtained with the commercial 4-META/MMA-TBB resin system. A model experimental study concerning the molecular weight of poly (MMA) formed in the presence of some copper salts suggested that the increase in bond strength was produced through an increase in molecular weight of MMA-TBB resin by the copper salts.
Acid Etching, Dental↗
Lead immobilization using phosphoric acid in a smelter-contaminated urban soil.
Transformation of soil lead (Pb) to pyromorphite, a lead phosphate, may be a cost-effective remedial strategy for immobilizing soil Pb and reducing Pb bioavailability. Soil treatment using phosphoric acid (H3PO4) was assessed for its efficacy to reduce Pb solubility and bioaccessibility. Soil containing 4,360 mg of Pb kg(-1), collected from a smelter-contaminated site in Joplin, MO, was reacted with 1,250, 2,500, 5,000, and 10,000 mg of P kg(-1) as H3PO4. The reaction was followed by measurements of Pb bioaccessibility, solubility products, and microprobe analyses. Soluble Pb concentration in the soil decreased with increasing H3PO4 addition. Adding 10,000 mg of P kg(-1) reduced bioaccessible Pb by 60%. The logarithm of bioaccessible Pb decreased as a linear function of increasing H3PO4 addition with an R2 of 0.989. A higher soil/solution ratio was required to extract bioaccessible Pb after the treatment. Microprobe analyses showed that the Pb particles contained P and Cl after the reaction, and the spectra generated by the wavelength-dispersive spectrometer were similar to those of synthetic chloropyromorphite. Lead solubility in the P-treated soil was less than predicted for hydroxypyromorphite [Pbs(PO4)3-OH] and greater than predicted for chloropyromorphite [Pbs(PO4)3Cl]. The P treatment caused approximately 23% redistribution of soil Pb from the clay and silt size fractions to the sand fraction. Soil treatment with H3PO4 resulted in the formation of a compound similar to chloropyromorphite and reduced bioaccessibility of soil Pb, which may have a potential as an in situ technique for Pb-contaminated soil remediation.
Biological Availability↗
The effect of fluoride in phosphoric acid on enamel fluoride uptake and the tensile bond strength of an orthodontic bonding resin.
Decalcification that occurs adjacent to bonded orthodontic brackets is of great concern to orthodontists. Among the many procedures suggested to overcome this problem is the addition of fluoride to the phosphoric acid (H3PO4) etching solution. The purposes of this study were to determine the loss of fluoride from the acidic etching solutions, to evaluate the effect of various fluoride concentrations in H3PO4 on the tensile bond strength of an orthodontic bonding resin, to determine the amount of total and bound fluoride acquired by etched enamel, and to evaluate the effect of these etching solutions on enamel by scanning electron microscopy. Solutions of 50 m/m% H3PO4 containing 0 and approximately 0.01, 0.04, 0.08, 0.2, 0.4 and 0.9% fluoride were prepared. The fluoride concentrations in the etching solutions remained stable up to 3 months after preparation. The tensile bond strengths of the bonding resin to the etched enamel surfaces were not significantly different. Enamel acquired the greatest amount of total fluoride from H3PO4 solutions containing 0.215% fluoride while the bound fluoride acquired by enamel from the fluoride-containing etching solutions was not significantly different. The addition of fluoride to H3PO4 did not impede the etching effect on enamel.
Acid Etching, Dental↗