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PubMed1975

The use of 50 per cent phosphoric acid as an etching agent in orthodontics: a rational approach.

The chemical treatment of enamel surfaces is an approach used in obtaining increased adhesion of dental materials to tooth surfaces. One of the conditioning solutions extensively used prior to the direct bonding of orthodontic attachments is a 50 per cent phosphoric acid solution. The object of this investigation was to study the effect of various concentrations of phosphoric acid on the bond strength of an epoxy adhesive formulation developed for the direct bonding of orthodontic attachments. Furthermore, an attempt was made to quantitate the etching action of the phosphoric acid solutions by determining the depth of etch on polished enamel surfaces and recording the surface profiles of etched enamel surfaces by means of a surface-roughness measuring instrument. The use of 50 per cent phosphoric acid solution as a conditioning agent prior to the use of the epoxy adhesive formulation is advocated. The rationale supporting this recommendation includes (1) the bond strength of the epoxy adhesive system to enamel surfaces etched with 50 per cent H3PO4 is not significantly improved by the use of phosphoric acid at any other concentration; (2) the depth of etch obtained with 50 per cent H3PO4 is less than that observed with H3PO4 solution at concentrations which produce comparable bond strengths; (3) the surface roughness of enamel surfaces etched with 50 per cent H3PO4 is greater than that obtained with more dilute acid solutions. The optimal phosphoric acid concentration should be determined for each adhesive system.

Dental Bonding↗
PubMed2005

Phosphoric acid incorporated with acidulated phosphate fluoride gel etchant effects on bracket bonding.

The aim of this study was to evaluate the effects of etching with phosphoric acid incorporated in an acidulated phosphate fluoride (APF) gel on the bonding of a bracket and the loss of sound enamel. In the control group, the enamel was etched with 37% phosphoric acid for 30 seconds. In the experimental groups, the enamel was etched for 30 seconds with 37% phosphoric acid blended with 1.23% APF gel at various ratios (25%, 33%, 50%, 67%, and 75% APF gel). The brackets were bonded with Transbond XT light-cured orthodontic adhesive according to the manufacturer's instructions. The specimens were then treated under three different conditions: 37 degrees C for one hour, 37 degrees C for 24 hours, and thermocycling (2500 times) between 5 degrees C and 55 degrees C in deionized water. The shear bond strength of 10 specimens in each condition was measured and the results analyzed using a Tukey multiple comparison test (P = .05). The shear bond strength decreased significantly as the fraction of the APF gel increased in the experimental etchant. An apparent increase in the adhesive remnant index score was also observed in the large fraction of the APF gel. To minimize the damage of the sound enamel surface during the etching and debonding procedures, a mixture of phosphoric acid and an APF gel (50% and 67% APF fraction) can be used as an phosphoric acid etchant substitute without loss of the proper bracket bond strength.

Acid Etching, Dental↗
PubMed1995

Phosphoric acid entrapment leads to apparent protein heterogeneity.

Recombinant proteins produced in prokaryotes or eukaryotes show certain types of heterogeneity due to post-translational modifications. Some preparations of a soluble interferon gamma receptor, produced in Escherichia coli, appeared as a double band with slightly different mobilities in non-reducing sodium dodecylsulfate and native polyacrylamide gels. Ion spray mass spectrometry showed that the two forms had a mass difference of one to three multiples of 97 +/- 2 D. Gas chromatography-mass spectrometry analysis revealed the presence of phosphoric acid in the hydrolysate and in the intact protein. The more slowly migrating protein species had trapped molecules of phosphoric acid during the protein extraction. Most of the trapped phosphoric acid was loosely associated with the protein. One to three molecules were tightly, but non-covalently linked per receptor molecule. Phosphoric acid entrapment did not affect biological activity and most likely did not affect protein conformation. The species carrying phosphoric acid showed higher solubility. Trapping of phosphoric acid by proteins may be a general phenomenon and the results reported here thus useful in the characterization of other recombinant proteins.

Chemical Phenomena↗
PubMed1990

[Development of dental quick casting with zircon-phosphoric acid investments].

The application of zircon (ZrSiO4) that has high refractoriness, high thermal conductivity and a low coefficient of thermal expansion, to quick casting investment was studied. Various zircon powders and phosphoric acid solutions were tested with respect to the higher thermal shock resistance. The formulation and properties of zircon-phosphoric acid investment materials such as water/powder ratio, fluidity of slurry, setting time, setting expansion, thermal expansion, thermal analysis, green and fired compressive strength were measured. Formulation of zircon slurry for coating was zircon flower #600 30%, zircon flower #350 10%, and zircon sand CP 60%, and that for sanding was zircon flower #200. The mixing liquid was 15% phosphoric acid and liquid/powder ratio was 0.1. The slurry using phosphoric acid had good fluidity and good workability. The 24-hour green strength was 1 MPa, fired strength was 10 MPa, 24-hour setting expansion was -0.04% and the thermal expansion at 1000 degrees C was 0.31%. Immediately after coating with zircon slurry, the coating layer was dried, sintered and dewaxed by thermal shock. The thermal shock consisted of the following four-step manipulations. The first is hot air drying (50 degrees C, 5 minutes), the second is heat shock (900 degrees C, 3 seconds), the third is redrying (220 degrees C, 3 minutes) and the fourth is dewaxing (550 degrees C, 3 minutes). Small casting of pure titanium and K-metal could be done successfully by the quick casting method using the zircon-phosphoric acid investments. It was found that the total expansion of the secondary investments influenced the casting adapatability.

Dental Casting Investment↗
PubMed1975

Effect of carbonated beverages and of an antiemetic containing carbohydrate and phosphoric acid on riboflavin bioavailability and salicylamide biotransformation in humans.

Two carbohydrate-phosphoric acid solutions, one a widely used beverage (Solution C) and the other a pharmaceutical product used as an antiemetic (Solution E), administered together with riboflavin-5'-phosphate or salicylamide to healthy human adults, significantly increased the bioavailability of riboflavin and appreciably altered the metabolic fate of salicylamide (increased conversion to the sulfate and decreased formation of the glucuronide). A beverage containing phosphoric acid but no carbohydrates (Solution T) also increased the bioavailability of riboflavin but not as much as Solution C. These effects are attributed to a decrease of the gastric emptying rate caused by carbohydrates and phosphoric acid, consistent with the empirical use of Solution C syrup and Solution E as antinauseants and antiemetics. The results demonstrate also that the choice of beverage to be taken with medication can affect the bioavailability and/or metabolic fate of medicinals with saturable absorption and/or biotransformation characteristics.

Adult↗
PubMed1989

[Investigation into the effect of citric and phosphoric acids on planed root surfaces using S.E.M].

The aim of the present study was to evaluate the effect of citric and phosphoric acid conditioning the diseased root surface on periodontally extracted teeth. Citric acid pH1 and 50 per cent phosphoric acid were topically applied to thoroughly scaled and planed root surfaces for one to three minutes. The specimens were then processed for scanning electron microscopy (S.E.M.) Root surfaces that had received acid treatment after root planing exhibited no smear layer and the overall surface appeared to have an undulating morphology. Whereas, examination of nonacid-treated specimens showed the presence of a smear layer. Furthermore, phosphoric acid treated surfaces demonstrated more irregularity with increasing application time.

Acid Etching, Dental↗
PubMed1981

Preparation of Schiff-type dye-SO2 reagents with phosphoric acid and their cytochemical properties.

A new method employing phosphoric acid in place of hydrochloric acid for the preparation of azure A-SO2 and toluidine blue O-SO2 has been described in this communication. It has been found that o-phosphoric acid in a weak concentration can be a suitable substitute for hydrochloric acid in the preparation of these dye-SO2 reagents. These dye-reagents produce excellent blue nuclei in human uterine tumour. Toluidine blue O-SO2 fortified with an amino aicd, glycine also produces excellent blue chromosomes in the squash preparations of grasshopper testes fixed in acetic acid-alcohol. The shelf-life of these two dye-reagents has also been presented herein.

Animals↗
PubMed1996

Variation in phosphoric acid concentration and treatment time and HEMA diffusion through dentin.

PURPOSE: The effects of phosphoric acid concentration and time of dentin treatment on the movement of 2-hydroxyethylmethacrylate (HEMA) from a bonding resin-resin composite combination through dentin were investigated in vitro. MATERIALS AND METHODS: Freshly extracted human third molar teeth were divided into seven groups each of 10 teeth. A closed chamber was attached to the CEJ of each tooth to contain 1 ml distilled water. An occlusal cavity of 6 mm diameter and remaining dentin thickness of 1.0-1.5 mm was prepared in each tooth. Dentin was treated with either 10% phosphoric acid for 15, 30 or 60 seconds or with 37% phosphoric acid for 15, 30 or 60 seconds. A control group not treated with acid was also prepared. The cavities were rinsed, dried and then treated with the HEMA-containing Scotchbond Multi-Purpose bonding resin which was light-cured for 10 seconds. The cavities were then restored with Z100 and light-cured for 30 seconds. Water samples were retrieved from the chambers over a time course (4.32, 14.4, 43.2, 144 & 432 minutes; 1, 3 and 10 days) and analyzed by high performance liquid chromatography. RESULTS: HEMA was detected in the pulp chambers of all teeth from 4.32 minutes after resin placement. Mean total (cumulative) release at 10 days for all groups was in the 2-4 mumol range. The highest HEMA diffusion rate was 4.32 minutes after placement and were in the range 6-13 times greater than control in the 10%-15 seconds, 10%-30 seconds, 10%-60 seconds, 37%-15 seconds, and 37%-30 seconds groups. Unexpectedly, by far the lowest early rate at 4.32 minutes was in the 37%-60 seconds group (0.6 times of no-acid control).

Acid Etching, Dental↗
PubMed1995

Phosphoric acid as a conditioning agent in the Gluma bonding system.

PURPOSE: To investigate the effect of phosphoric acid conditioning gels on compatibility with the Gluma dentin bonding system. MATERIALS AND METHODS: Sheer bond strengths (BS), marginal performance in dentin cavities and microleakage resistance in mixed cavities were used as target parameters to determine the efficacy of Gluma/Pekafill on dentin pretreated with conditioners of 5, 10, 20 or 35% H3PO4 and different amounts of silica (0, 5 and 10%) after 15, 30 60 or 120-second treatment duration. The thicknesses of the hybrid layers were determined along the dentin cavity margin by light microscopy. RESULTS: Neither the phosphoric acid concentration and the silica content nor the conditioning times tested had a significantly different effect on SBS or marginal performance (P > 0.05). There was no relationship between the hybrid layer thickness and the target parameters either. The SBS recorded on dentin were in the same order of magnitude as previously found on acid etched enamel (+/- 17 MPa). The marginal performance and microleakage results after thermocycling proved adequate dentin bonding and cavity sealing. Phosphoric acid etching of dentin is compatible with the gluma bonding system.

Acid Etching, Dental↗
PubMed1999

Five year evaluation of class III composite resin restorations in cavities pre-treated with an oxalic- or a phosphoric acid conditioner.

An oxalic acid solution has been proposed as a conditioning agent for resin composite restorations in two commercial adhesive systems. The durability of 163 class III restorations, including 12 class IV restorations, in cavities pre-treated with an oxalic acid total etch technique or an enamel etch with phosphoric acid was studied. Each of 52 patients received at least one of each of three experimental restorations. The restorations were evaluated yearly with slightly modified United States Public Health Service (USPHS) criteria. After 5 years 95% of the restorations were evaluated as acceptable. Reasons for failure were the fracture of four fillings, including three class IV, secondary caries contiguous to two fillings and a non-acceptable colour match for one restoration. For eight class III restorations a fracture of the incisal tooth structure was registered. No differences were seen between the three experimental restorations.

Acid Etching, Dental↗
PubMed1992

Effect of dietary phosphoric acid supplementation on acid-base balance and mineral and bone metabolism in adult cats.

Experimental evidence indicates that maintenance of urinary pH < or = 6.4 is the single most effective means of preventing feline struvite crystalluria or urolithiasis of noninfectious causes. This may be accomplished by dietary acidification, but must be moderated to avoid potential adverse effects of excessive acidification, including bone demineralization, negative calcium balance, potassium depletion, and renal disease. Effects of chronic dietary phosphoric acid supplementation on acid-base balance and on mineral and bone metabolism were investigated in adult, domestic cats. One group of 6 cats was fed a basal, naturally acidifying diet without added acidifiers, and another group of 6 cats was fed 1.7% dietary phosphoric acid. Changes observed during 12 months of study included development of noncompensated metabolic acidosis, increased urinary calcium excretion, and lower but positive calcium balance in cats of both groups. Urinary pH decreased in cats of both groups, but was significantly (P < 0.05) and consistently maintained < or = 6.4 in cats given dietary phosphoric acid. Urinary phosphorus excretion increased in cats of both groups, but was significantly (P < 0.05) greater in phosphoric acid-supplemented cats, leading to lower overall phosphorus balance as well. Potassium balance decreased in cats of both groups, but was only transiently negative in the phosphoric acid-supplemented cats midway through the study, and normalized at positive values thereafter. Plasma taurine concentration was not affected by dietary acidification, and remained well within the acceptable reference range for taurine metabolism. Double labeling of bone in vivo with fluorescent markers was followed by bone biopsy and histomorphometric measurement of several static and dynamic variables of bone formation. Overall indices of bone formation decreased in cats of both groups with age and confinement, but were not affected by dietary phosphoric acid supplementation. Dietary supplementation with phosphoric acid used as the principal inorganic P source to achieve moderate and stable degree of urinary acidification, did not appear over the course of 1 year, to have induced adverse effects on mineral, bone, or taurine balance in these adult domestic cats.

Acid-Base Equilibrium↗
PubMed2000

Calcium leaching from dentin and shear bond strength after etching with phosphoric acid of different concentrations.

Based on the H2O-P2O5-CaO phase diagram, we hypothesize that a phosphoric acid concentration around 27 wt% leaches most calcium from dentin. We also hypothesize that bond strength is affected by resin infiltration, and that resin infiltration becomes incomplete when calcium leakage exceeds a certain value. Dentin disks were cut from human molars. Eight phosphoric acid concentrations were prepared (15.7-51.2 wt%). For each acid group, there were four etch time subgroups (15, 30, 60 and 120 s). The dentin disks were etched in acid and rinsed in water for times corresponding to 15 s, 30 s, 60 s and 120 s. The calcium concentrations were analyzed using atomic absorption spectroscopy. Composite cylinders were bonded to the remaining parts of the teeth using the same etching protocol, and shear bond strength was determined. The 29.2 wt% group demonstrated the highest and the 15.7 wt% group the lowest calcium leaching value. Even though there were trends towards lower bond strength for longer etch times, a statistically significant difference was only found between 30 and 120 s. There was no significant correlation between calcium leaching and bond strength. The results support the tested hypothesis that the highest leaching value would be around 27 wt% phosphoric acid.

Acid Etching, Dental↗
PubMedDate not supplied

Extraction behavior of hemoglobin using reversed micelles by dioleyl phosphoric acid.

A new surfactant, dioleyl phosphoric acid (DOLPA), has been applied to the extraction of hemoglobin using reversed micelles. The reversed micelles formed by DOLPA can easily extract hemoglobin from aqueous to reversed micellar solutions. DOLPA is the first surfactant to extract hemoglobin completely without using any cosurfactants. On the basis of the difference between DOLPA and AOT reversed micelles in the forward extraction behavior of hemoglobin, the nature of the interfacial complex that would be formed between surfactants and hemoglobin at the oil--water interface was found to be the dominant factor in determining the extraction efficiency of hemoglobin be reversed micelles. In addition, back-transfer studies of hemoglobin from the DOLPA reversed micelles were also carried out by the phase transfer method. It was found that hemoglobin, once dissolved into the DOLPA reversed micelles, is not transferred to a fresh aqueous solution even when the conditions are adjusted to not allow the forward transfer of hemoglobin. However, the addition of several kinds of alcohol drastically improved the yield in the back-transfer of hemoglobin. The efficiency in the back-transfer of hemoglobin strongly depends on the aqueous conditions that are in contact with the reversed micelles, such as pH, ionic strength, and alcohol concentration. A pH higher than the pI of hemoglobin, a salt concentration lower than that of the water pool, and the proper concentration of alcohol are required for the recovery aqueous phase to ensure the back-transfer of hemoglobin from the DOLPA reversed micelles.

Alcohols↗
PubMed1995

Phosphoric acid tooth conditioner containing copper salt for bonding MMA-TBB resin.

The purpose of this study was to examine the feasibility of a conditioner for treating enamel and dentin simultaneously for MMA-TBB resin bonding. Various phosphoric acid solutions containing copper salts were prepared and used as conditioners before bonding MMA-TBB resin to bovine teeth. Their effects on the surface morphology and bonding were studied by scanning electron microscopy and tensile bond strength testing. The concentrations of phosphoric acid as well as copper salts therein affected the bond strength to dentin. Ten percent phosphoric acid containing 3% copper (II) chloride appeared optimal for treating dentin and was significantly effective in improving the bond strength compared with phosphoric acid alone. This conditioner was applicable also to enamel without any adverse effect on the bond strength. Therefore, enamel and dentin may effectively be treated simultaneously with this conditioner before bonding of MMA/TBB-based resin.

Acid Etching, Dental↗
PubMed2000

The effect of phosphoric acid concentration on resin tag length and bond strength of a photo-cured resin to acid-etched enamel.

OBJECTIVES: To determine the relationship between depth of penetration and tensile bond strength of a photo-cured resin to phosphoric acid etched enamel, and the efficacy of enamel etchants that are less aggressive than a concentration of 10% H3PO4. METHODS: The tensile bond strength and length of tags produced by a photo-cured (20 s) resin consisting of pre-polymerized TMPT/silica in 3% HNPM-TEGDMA on acid-etched enamel was determined. The enamel etchants tested were various concentrations (3-65%) of phosphoric acid. The resin was applied to enamel samples that had been abraded with No. 600-grit SiC paper and acid etched (30 s) to create test specimens that were loaded to fracture on a testing device. The HCl-treated, then cut specimens, were examined under scanning electron microscopy and light microscopy. RESULTS: The tensile bond strength (10 MPa) of resin to enamel, pre-treated with various acid concentrations did not vary significantly. But resin tag length was found to decrease significantly from 22 microns for 35% H3PO4 to 12 microns for 20% H3PO4 to 9 microns for 5, 10 and 65% H3PO4 to 5 microns for 3% H3PO4. SIGNIFICANCE: These findings suggest that the length of the tags created by the tested photo-cured resin on phosphoric acid-etched enamel contributes little to the bond strength of the test specimens, and that the adhesive strength of the resin to H3PO4 etched enamel is mainly attributable to the resin's ability to penetrate between the enamel crystallites and rods. Further, enamel pre-treatment by phosphoric acid etchants of concentrations lower than 10% may be satisfactorily employed. The use of less aggressive acid concentrations might minimize any potential adverse effects to enamel substrates.

Acid Etching, Dental↗
PubMed1984

[Determination of free silica in airborne dust by phosphoric acid method].

Free silica content in airborne dust was measured with a modified procedure collecting sample dust on glass fiber filter and heating the dust together with the filter in phosphoric acid. The insoluble phosphoric acid residue of the glass fiber filter used by us was of small amount. Fifteen mg of dust was enough to determine its free silica content correctly. On dust collected at pottery and foundries works, satisfactory coincidence was found between the values of free silica content by our procedure and by X-ray diffraction. It can be concluded that this is a reliable method for determination of free silica content of airborne dust as well as of deposited one.

Air Pollutants, Occupational↗