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PubMed1983

Ultrastructural study of new connective tissue attachment following phosphoric acid application on human root dentin.

THE PRESENT STUDY was undertaken to verify whether acid conditioning of the root surface can promote new connective tissue attachment in man. A flap was raised over two maxillary central incisors, with 6-mm pockets, which had to be extracted in a 72-year-old woman. Following root planning, a rectangular area was delineated by a groove on the buccal surface of the teeth. Inside these limits, cementum was removed and the denuded dentin was etched with a 50% gelified phosphoric acid solution (pH, 1.3) for 1 minute and the flap was repositioned. Forty-two days later, the experimental teeth were extracted, and undecalcified specimens were prepared routinely for transmission electron microscopy. Results showed that new connective tissue attachment had occurred between healing connective tissues and acid-treated dentin surface, with functionally oriented Sharpey's fibers. The mechanism of new connective tissue attachment could be observed as a typical cementum crystallites deposition on a denuded dentin matrix coupled with an active collagen fibrils synthesis. This process resulted in the incorporation of fibers into the new superficial layer of cementoïd tissue.

Aged↗
PubMed1998

On the Reaction of Phosphorous Acid with Superacids and the Crystal Structure of H(5)O(2)(+)SbF(6)(-) and Me(4)N(+)HPF(5)(-).

Phosphorous acid reacts with the superacidic system HF/SbF(5) with formation of HPF(4), water, and oxonium hexafluoroantimonate, which crystallizes as H(5)O(2)(+)SbF(6)(-) in the triclinic space group P&onemacr; with a = 6.492(6) Å, b = 7.469(8) Å, c = 8.095(6) Å, alpha = 116.17(7) degrees, beta = 93.90(7) degrees, and gamma = 112.34(7) degrees, with two formula units per unit cell. The unit cell contains two H(5)O(2)(+) ions of approximate symmetry C(2)(h)() with an intramolecular O.O distance of 2.418(8) or 2.40(1) Å, respectively. The reaction is discussed with regard to the formation of protonated species in various superacidic media. In addition the crystal structure of Me(4)N(+)HPF(5)(-) which is formed by the reaction of HPF(4) with Me(4)N(+)F(-) is reported. The salt crystallizes in the tetragonal space group P4/nmm with a = 8.564(5) Å and c = 5.687(2) Å, with two formula units per unit cell. The P-F distances of P-F(eq) = 1.595(6) Å and P-F(ax) = 1.594(9) Å for the psi-octahedral HPF(5)(-) show no significant interaction exercised by hydrogen on the cis- and trans-fluorine.

Journal Article↗
PubMed2003

Alterations in human enamel surface morphology following the use of an office bleaching agent and consecutive application of 37% phosphoric acid in vivo.

OBJECTIVE: The aim of this in vivo study was to evaluate the effects of a visible light-activated in-office bleaching agent, Opalescence Xtra (35% hydrogen peroxide) on the external enamel surface of human teeth by using scanning electron microscopy (SEM). METHODS: The labial surfaces of nine upper incisors from nine different patients were divided into four parts, and a bleaching agent was applied to the mesial halves of the teeth. Three weeks following this treatment, the teeth were extracted and divided into four quadrants. Each quadrant was treated with a different procedure and the samples were examined under SEM. The SEM photographs were blindly evaluated by a jury of four experts. RESULTS: Although there were no statistical differences in the rating of surface morphology of bleached and control groups, the 37% phosphoric acid etched and acid etched + bleached enamel samples demonstrated a statistically significant dissimilar surface morphology (p < 0.05). CONCLUSION: The bleached + etched enamel treatment showed an uneven etched surface compared to the acid etched control.

Acid Etching, Dental↗
PubMed1986

[The role of phosphoric acid residues in the formation of antigenic determinants of the structural components of DNA].

The inhibitory activity of thymidine, thymidine triphosphate and thymidyl oligonucleotides was studied in thymidine-antithymidine antibodies reaction. Thymidine was shown to have the greatest inhibitory effect, with thymidine triphosphate and thymidyl oligonucleotide inhibitory activity less expressed and reducing with the increase in oligonucleotide length. The effect of thymidine, thymidine triphosphate and thymidyl oligonucleotides on the interaction of antisera and SLE patients' sera with denatured DNA was studied. It was shown that thymidine triphosphate and particularly thymidyl oligonucleotides are characterized by greater inhibitory capacity, as compared to thymidine. It was found that only thymine dimers bound by phosphate groups can inhibit the interaction of UV-irradiated DNA with antiserum specific for UV-modified DNA. The data obtained suggest that the charge determined by phosphoric acid residues plays an essential role in the interaction of antibodies induced to charged structural DNA components.

Antibodies, Antinuclear↗
PubMed1979

The phosphorus excretion pattern and balance during one egg cycle of the laying hen fed a phosphorus deficient diet with or without a single dose of phosphoric acid.

A balance trial was conducted to study the phosphorus excretion pattern of laying hens in relation to egg cycle. Excreta were collected quantitatively at 4, 8, 12, and 24 hr after oviposition. The amount of feed consumed corresponding to the excreta collected at a specific time interval was calculated using chromic oxide as a marker. The percent recovery of chromic oxide with laying hens was 73.97 +/- .56%. The maximum apparent digestibility of the dietary phosphorus, all of plant origin, was estimated to be 28.9 +/- 3.1% during 0 to 4 hr after oviposition when the endogenous excretion of phosphorus was theoretically minimized. Laying hens fed a diet containing .30% phosphorus excreted 24.3 mg less phosphorus than intake during the day, indicating that hens had to withdraw approximately 100 mg of phosphorus from their body to produce an egg. These hens excreted 63.1 +/- 27.0 mg of endogenous phosphorus during the 24 hr period, most of which was excreted during the period between 12 to 24 hr after oviposition of the previous egg. The excretion pattern of phosphorus was closely related to the egg laying cycle of the hen. Hens dosed with 100 mg of phosphorus, as a phosphoric acid solution, excreted more phosphorus than the undosed control birds. Approximately 45 mg of 100 mg of the phosphorus dose were excreted during the 24 hr period. At least 84.8 mg of the dosed phosphorus were absorbed within 12 hr and a part of it was excreted during the later period. Data indicated that the true absorption rate of the dosed phosphorus might have been much faster.

Animal Feed↗
PubMed1996

Determination of the O/M ratios of polynary uranium oxides by Ce(IV)-Fe(II) back titration after dissolution in mixed sulphuric and phosphoric acids.

Uranium (IV) in polynary uranium oxides is determined after the solid has been dissolved in a warm mixed solution of sulphuric and phosphoric acids containing excess Ce(IV). The latter is titrated with a Fe(II) standard solution using ferroin as indicator. This method is especially effective for (mixed) uranium oxides which are difficult to dissolve in hot Ce(IV) sulphuric acid. The standard deviation of the determined x value in polynary oxides is estimated to be below +/- 0.004 for samples of 10-30 mg.

Journal Article↗
PubMed2004

Surface modification with phosphoric acid of SiO2/Nb2O5 prepared by the sol-gel method: structural-textural and acid sites studies and an ion exchange model.

In this work, the structural and textural properties of the SiO2/Nb2O5 system prepared by the sol-gel method and then modified by phosphoric acid were studied. The different materials were prepared, with three different mol % Nb2O5 (2.5, 5.0, and 7.5 mol %), and calcined in the temperature range of 423-1273 K. BET specific surface area determinations, scanning electron microscopy connected to a X-ray emission analyzer, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS) were used for the investigation. For the lowest temperature of calcination (423 K), the mesopores and micropores of the modified material were blocked, resulting in a decrease of the specific surface area compared to the SBET values obtained for the SiNb matrix. Under intermediate temperatures of calcination (423-873 K), the modified material acquired textural stability. By XPS analysis, the presence of the dihydrogenphosphate species was identified, the P/Nb atomic ratios being independent of the thermal treatment. 31P magic angle spinning NMR confirmed the XPS data and also showed that the chemical shift of the (H2PO4)- ions strongly depended on the crystallization degree of the Nb2O5. Structural thermal stability was also shown by the presence of Brønsted acid sites in the modified material calcined at high temperature (1273 K). The thermal stability is directly associated with obtainment of the same value for K+ exchange capacity (0.74 mmol g(-1), average value) for the modified materials calcined at 423 and 1273 K. The chemical analyses of phosphorus for the modified materials were made by using the inductively coupled plasma. The value was 0.36 mmol g(-1), corroborating the presence of (H2PO4)- ions. The ion exchange isotherms presented an S-shaped form characteristic of energetically heterogeneous ion exchangers, permitting application of a model of fixed polydentate centers, in which ion exchange took place.

Journal Article↗
PubMed2001

Effect of level of acidification by phosphoric acid, storage temperature, and length of storage on the chemical and biological stability of ground poultry mortality carcasses.

Two experiments were conducted to evaluate the addition of feed-grade H3PO4 in comparison to lactic acid fermentation as a means of preserving ground poultry mortality carcasses. Mortality silage quality in both experiments was evaluated by measuring the rise in pH after initial acidification (deltapH) and the content of nonprotein N (NPN), volatile nitrogen (VN), NH3-N, and fecal coliform bacteria in the silage treatments. Preliminary work in Experiment 1 evaluated the preservative effects of six initial levels of acidification with H3PO4 (pH 2.0, 2.5, 3.0, 4.0, or 5.0) at two storage temperatures (21 and 45 C). Experiment 2 compared silages preserved with different levels of feed-grade 74.5% H3PO4 (4.13, 5.52, 6.90, and 8.28% wt/wt, concentrated acid basis) to silages made by lactic acid fermentation. Based on the evaluations in Experiment 1, acidification with H3PO4 to pH < or = 3.0, when incubated at 45 C, or pH < or = 2.0, when incubated at ambient temperatures, produced the most biologically favorable poultry mortality silage for subsequent use as a feed ingredient. In Experiment 2, mortality silages containing 8.28% H3PO4 (wt/wt, concentrated acid basis) contained significantly (P < 0.05) lower levels of the protein degradation by-products VN and NH3-N than silages prepared by lactic acid fermentation. Therefore, feedstuffs manufactured from mortality silages prepared using 8.28% H3PO4 would be expected to result in improved animal performance vs. feedstuffs manufactured using silages prepared by lactic acid fermentation.

Animals↗
PubMed2006

Phosphoric acids as amplifiers of molecular chirality in liquid crystalline media.

[structure: see text] A new system for the double amplification of the molecular chirality of simple chiral amines in achiral liquid crystalline media is described. It involves a conformationally flexible phosphoric acid based receptor that by binding to chiral amines induces chirality in the liquid crystalline matrix. Efficient cholesteric phase formation was shown by several chiral amines that were not able to induce measurable helicity in nematic liquid crystals by themselves.

Journal Article↗
PubMedDate not supplied

Effect of self-etching primer vs phosphoric acid etchant on bonding to bur-prepared dentin.

This study evaluated the effect of dentin conditioner on tensile bond strength to dentin prepared with different types of burs. A self-etching primer system, Mac-Bond II (MB, Tokuyama Dental) and a phosphoric acid etching system, Single Bond (SB, 3M) were used for conditioning. Twenty-four extracted intact human molars were ground flat to expose occlusal dentin. After the dentin surfaces were polished with #600 SiC paper, the teeth were randomly divided into a control group and three experimental groups according to the bur grits used: #600 SiC paper only as the control, fine cut steel bur (SB600), crosscut steel bur (SB703) and regular grit diamond bur (DB) mounted in a dental handpiece utilizing water cooling. The dentin surfaces were treated with one of two adhesive systems, then composite buildups were done with Clearfil AP-X (Kuraray Medical). After soaking the bond specimens for 24 hours in 37 degrees C water, multiple vertical serial sections (0.7 mm thick, 7-8 slices per one tooth) were made, trimmed to form an hour-glass shape with a 1.0 mm2 cross-section and tensile bond strengths were determined at a crosshead speed of 1 mm/minute. Statistical analysis was made using one and two-way ANOVA and Fisher's PLSD test (p<0.05). Six additional molars were used for SEM observations of the dentin surfaces of each group before and after treatment with the self-etching primer of MB, and another four teeth were used to observe the resin-dentin interface of each group of SB. Using MB, the DB group produced the lowest tensile bond strength (TBS) among the groups that received bur preparation, and there were no statistical differences among SB600, SB703 and the control. For SB, the TBS of SB703 was the highest, and there were no statistical differences among the other groups and the control. The influence of the method used to prepare dentin for micro-tensile bond strength testing was dependent on the adhesive system used.

Acid Etching, Dental↗
PubMed2002

In vitro lead bioaccessibility and phosphate leaching as affected by surface application of phosphoric acid in lead-contaminated soil.

Phosphate treatment of lead-contaminated soil may be a cost-effective remedial alternative for in situ stabilizing soil Pb and reducing Pb toxicology to human. The leaching behaviors of the P added to soil surface and the effect on subsurface Pb bioaccessibility must be addressed for this remedial technology to be acceptable. A smelter-contaminated soil containing an average of 2,670 mg Pb kg(-1), collected from the Jasper County Superfund Site located in Jasper County, Missouri, was surface treated with 10 g P kg(-1) as phosphoric acid (H(3)PO(4)). Following a simulated column leaching and 90-day treatment of field plots, respectively, bioaccessible Pb, P, and pH in soil profile were measured. Surface treatment using H(3)PO(4) effectively stabilized soil Pb and reduced leachable Pb and the bioaccessibility. Phosphate leached into deeper profile significantly lowered bioaccessible Pb in subsurface. Reduction of Pb bioaccessibility increased as a linear function of increasing soil P. Although surface H(3)PO(4) treatment resulted in an enhanced leaching of added P and may increase potential risk of surface and groundwater pollution, the P leaching under field conditions is very limited. Lime addition following the treatment may reduce the leachability of added P and further immobilize soil Pb.

Animals↗
PubMed1978

Some kinetic aspects of the mechanism of hydrolysis of phosphoric acid esters by nonspecific acid phosphatase from Schizosaccharomyces pombe.

1. The kinetics of the hydrolysis of nitrophenylphosphate by nonspecific acid phosphatase (orthophosphoric-monoester phosphohydrolase (acid optimum), EC 3.1.3.2.) from Schizosaccharomices pombe was studied. 2. The kinetic parameters, Km and V, were determined as well as the inhibition constants, K1, for the inhibitors, phosphate and fluoride, as a function of pH. 3. The results, interpreted according to the theories of Dixon and Waley indicated the presence of three ionizable groups on the enzyme itself and one on the enzyme-substrate complex. 4. A model of the hydrolysis of phosphoric acid monoesters by the S. pombe acid phosphatase is proposed based on the ionization state of the reactants and on the results of the inhibition by the competitive inhibitors.

Acid Phosphatase↗