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PubMedDate not supplied

Self-etching primer vs phosphoric acid: an alternative concept for composite-to-enamel bonding.

The purpose of this in vitro study was (1) to investigate the composite-to-enamel bond strength and (2) to analyze the marginal adaptation of resin composite restorations in class 2 cavities using three self-etching priming agents in comparison to conventional phosphoric acid etching and bonding application. In the first part of the study 24 extracted bovine incisors were embedded in acrylic resin and ground flat with 800-grit paper. The following three self-etching priming agents/composite resins were applied to the enamel surfaces of six teeth each: Clearfil Liner Bond 2/Clearfil AP-X (Group I), Etch & Prime 3.0/Degufill mineral (Group II), Resulcin AquaPrime + MonoBond/Ecusit (Group III). In Group IV Ecusit-Mono/Ecusit was used after enamel etching with phosphoric acid (37%). Shear bond strength values measured on a T22 K testing machine at a crosshead speed of 1 mm/min were: 24.2 +/- 3.0 MPa (Group I), 21.9 +/- 1.4 MPa (II), 34.0 +/- 3.6 MPa (III), and 26.3 +/- 1.8 MPa (IV). ANOVA revealed significant (P < 0.05) differences in shear bond strength between groups, except comparison of Group I and II, and Group I and IV. In the second part of the study 24 standardized class 2 cavity preparations with the approximal box extending 1 mm above the CEJ were prepared in extracted human molars. Enamel margins were beveled and the teeth were divided into four groups of six teeth each. Cavities were restored using the self-etching priming agents Clearfil Liner Bond 2 (Group I), Etch & Prime 3.0 (Group II), and Resulcin AquaPrime + MonoBond (Group III). In Group IV composite resin restorations were placed after 37% phosphoric acid etching and bonding application (Ecusit-Mono). Quantitative SEM analysis of the marginal adaptation of the restorations after thermocycling (5-55 degrees C, 2500 cycles) and mechanical loading (100 N, 500,000 cycles) revealed excellent, gap-free margins in 91.2% (Group I), 93.0% (Group II), 92.0% (Group III), and 92.5% (Group IV) of the restorations' approximal area. There were no statistically significant differences between the four groups (P < 0.05). In conclusion, results of the present in vitro study indicate that use of self-etching primers may be an alternative to conventional phosphoric acid pre-treatment in composite-to-enamel bonding restorative techniques.

Acid Etching, Dental↗
PubMed1996

Pulpal response to dentin etched with 10% phosphoric acid.

PURPOSE: To histopathologically evaluate the effect of etching sound dentin with 10% phosphoric acid, in cavities prepared just within the DEJ on young patients. MATERIALS AND METHODS: Twenty-four orthodontic patients who required premolar extractions were selected for the study. Each of the patients had facial Class V resin composite restorations placed in two maxillary premolars selected for extraction. Each preparation was cut circular, 2 mm in circumference and 0.5 mm into dentin. The dentin of one maxillary premolar preparation, randomly selected, was etched with 10% phosphoric acid (Bisco) for 20 seconds. This was followed by the placement of a dentin bonding agent (All-Bond 2) and a microfilled composite restoration (Silux). The contralateral maxillary premolar, received a similar preparation, but the dentin surface was lined with a light-cured glass ionomer liner before etching of the enamel, followed by placement of a dentin bonding agent and a microfilled resin composite restoration. One of the mandibular premolars was randomly selected as a negative control, having no treatment. Fourteen days after the placement of the restorations, the teeth were extracted, and histologically examined for insult to the pulpal tissues. Injury to the pulp was evaluated by quantitative measures of histopathology, including necrosis, infiltration by inflammatory cells, and other indicators of tissue injury. RESULTS: Using a Kruskal-Wallis analysis, there was no statistically significant difference in pulpal histopathology of the teeth with etched dentin versus teeth with dentin protected by a liner or the negative control teeth (P < 0.05).

Acid Etching, Dental↗
PubMed1998

Effect of 10% phosphoric acid conditioning on the efficacy of a dentin bonding system.

The efficacy of a commercial total-etch wet-bonding dentin bonding system and the effect of conditioning using 10% phosphoric acid both on the Ca-content in the substrate dentin and on the efficacy of the experimental contraction gap-free dentin bonding system were evaluated by measuring the wall-to-wall polymerization contraction gap width of a commercial light-activated resin composite filled into a cylindrical cavity prepared in extracted human dentin. The Ca-content in the dentin was measured with an EDS. Complete marginal adaptation was obtained only in the experimental contraction gap-free dentin bonding system group. The Ca-content in the dentin was rapidly reduced by the 10% phosphoric acid conditioning. It was concluded that the dentist should not decalcify the dentin cavity wall possibly by using a dentin conditioner such as 10% phosphoric acid because the resin composite paste is apt to separate easily from the decalcified dentin cavity wall during polymerization.

Acid Etching, Dental↗
PubMed2005

A randomized controlled study evaluating the effectiveness of a two-step self-etch adhesive with and without selective phosphoric-acid etching of enamel.

OBJECTIVES: The purpose of this randomized controlled clinical trial was to test the hypothesis that a two-step self-etch approach is equally effective to restore cervical class-V lesions as a self-etch approach with beforehand selective etching of enamel using phosphoric acid. METHODS: Twenty-nine patients received two or four restorations randomly following two experimental protocols ('paired-tooth' study design): (1) A 'mild' self-etch adhesive (Clearfil SE, Kuraray) was applied following a self-etch approach on both enamel and dentin (C-SE non-etch); (2) Similar application of Clearfil SE, but including beforehand selective acid-etching of the enamel cavity margins with 40% phosphoric acid (C-SE etch). Clearfil AP-X (Kuraray) was used as restorative composite for all 100 restorations. The clinical effectiveness was recorded in terms of retention, marginal integrity and clinical micro-leakage after 2 years of clinical service. RESULTS: No restoration losses were recorded. Clinical micro-leakage was slight and only rarely observed. No significant differences were found between both groups for the diverse parameters evaluated except for the number of small incisal marginal defects, which was significantly higher in the C-SE non-etch group (McNemar: p = 0.0391). SIGNIFICANCE: The clinical effectiveness of the mild two-step self-etch adhesive Clearfil SE was excellent after 2 years of clinical service. Although in general no difference in clinical performance was recorded when Clearfil SE was applied following either of the experimental protocols, more marginal defects at the enamel side were noticed when enamel was not beforehand etched with phosphoric acid. However, these defects were small and of clinically negligible relevance.

Acid Etching, Dental↗
PubMedDate not supplied

Bond strength of a sealant to primary and permanent enamel: phosphoric acid versus self-etching adhesive.

PURPOSE: The objective of this study was to compare the effect of phosphoric acid and a self-etching adhesive on the short and long-term bond strength of a light-curing sealant to unground primary and permanent enamel. METHODS: A light-curing resin sealant (Delton Light Curing Pit & Fissure Sealant-CLEAR) was bonded to the flattest, peripheral surface of 40 primary and 40 permanent molars following conditioning of the cleaned enamel with 38% phosphoric acid or with the self-etching adhesive Prompt L-Pop (N=10/group). After either 1 week or 1 year in water, shear bond strengths were measured. Failure mode was determined in a stereo microscope. RESULTS: There was no significant difference in bond strengths between the phosphoric acid-etch and the self-etching adhesive groups, nor between the 1-week and 1-year results (P>.05). However, the bond strengths to primary enamel were lower than those to permanent enamel (P=.0021). The number of pure adhesive failures in each of the 8 groups varied between 0 and 3 (0-30%), and the remaining teeth displayed mixed adhesive-cohesive failures. CONCLUSIONS: The self-etching adhesive studied seems an attractive alternative to the acid-etch technique for sealant application in young children where simplifications in the clinical procedure are warranted.

Acid Etching, Dental↗
PubMed1992

Kinetics of hydroxyapatite dissolution in acetic, lactic, and phosphoric acid solutions.

The present study was undertaken in an attempt to relate the kinetics of hydroxyapatite dissolution to solution parameters, under experimental conditions relevant to the dental caries process. Thus, the dissolution of hydroxyapatite was studied in acetic, lactic, and dilute phosphoric acid solutions having initial pH values from 4 to 6. Rates of dissolution and the corresponding degree of saturation with respect to hydroxyapatite were determined at various times throughout the dissolution process. Rates of dissolution of all solutions were found to decrease with increasing degree of solution saturation and were greater in solutions with lower initial values of pH. However, rates of dissolution in partially saturated phosphoric acid solutions (without added organic acid) were at least one order of magnitude lower than those observed in the organic acid buffers with the same initial pH, over the same range of saturation values. The data obtained are consistent with a surface-controlled dissolution model in which the rate of dissolution is dependent upon the degree of saturation and the sum of the activities of the acidic species in solution, i.e., phosphoric and organic acids. These results suggest that in order to assess the cariogenic potential of a given medium (e.g., plaque fluid), one must determine both the degree of saturation with respect to the dissolving mineral and the activities of acidic species in solution.

Acetates↗
PubMed1995

Effect of reduction of phosphoric acid concentration on the shear bond strength of brackets.

The purpose of this study was to evaluate in vitro the effect of the reduction of phosphoric acid concentration on the shear bond strength of brackets to enamel. Twelve pairs of contralateral maxillary premolars were randomly divided into group 1 and group 2. Twelve additional upper premolars formed group 3. The three acid concentrations examined were 37% in group 1, 2% in group 2, and 5% in group 3. The buccal surfaces of the teeth were etched for 30 seconds, and metal brackets were bonded were Concise adhesive (3M Dental Products, St. Paul, Minn.). After storage of teeth in water at 37 degrees C for 1 week, a shear force was applied to the occlusal bracket wings in a direction parallel to the bracket base. The results showed that the mean shear bond strength after etching with 37% acid (x = 18.30 MPa) was significantly higher than that after etching with 2% acid (x = 15.28 MPa). The mean bond strength after etching with 5% acid (x = 16.49 MPa) was not significantly different from that after the use of the two other acids. The assessment of the Adhesive Remnant Index (ARI) showed that the amount of adhesive left on the teeth after debonding was smaller after etching with 2% acid than after etching with 37% acid or 5% acid. It was concluded that 2% phosphoric acid solution is appropriate for bonding of brackets. The reduced etching could be favorable in preventing enamel damage during the treatment and at the time of debonding.

Acid Etching, Dental↗
PubMed2004

Stabilisation of heavy metal containing dusts by reaction with phosphoric acid: study of the reactivity of fly ash.

Water-washed fly ash was reacted with phosphoric acid in order to transform available heavy metals into insoluble metal phosphate compounds. The temperature, pH and concentration of free phosphate were monitored during the first 80 min of reaction. Phosphoric acid reacted rapidly with second order kinetics and an apparent rate constant of 0.015 l/(mol s m2). Analysis of the evolution of the concentrations of other major elements of fly ash shows that the reaction follows a dissolution-precipitation type mechanism. The solubility of trace heavy metals tends to increase at low pH values. Various heat and mass transfer coefficients are derived and help understand the phosphate stabilisation procedure and design industrial reactors for this purpose. Calcium phosphates are formed which can trap heavy metals in a stable apatite mineral structure.

Carbon↗
PubMed2002

Automated trace anion determinations in concentrated electronic grade phosphoric acid by ion chromatography.

Modifications have been made to the method of ion-exclusion pre-separation followed by ion exchange with conductivity detection for the determination of trace levels of chloride, sulfate and nitrate in concentrated phosphoric acid. Ion-exclusion separation and pre-concentration of impurity anions is performed using Dionex AS6-ICE and AS11-HC (4 mm) columns, respectively, with water eluent. Final separation is performed using Dionex AG11-HC and AS11-HC (2 mm) columns, KOH gradient elution, and suppressed conductivity detection. Improvements to the method include addition of an autosampler and eluent generator, and use of external standard calibration. These instrumental and procedural changes significantly improve the method's throughput, while the method's capability relative to phosphoric acid specifications is maintained, as verified through statistical evaluation of control sample analyses. Detection limits of 60, 680, and 4,0 ppb (w/w) are obtained vs. semiconductor-grade phosphoric acid specifications of 1000, 12,000, and 5000 ppb for chloride, sulfate, and nitrate, respectively.

Anions↗
PubMed1994

Shear bond strength of a resin composite to enamel etched with maleic or phosphoric acid.

The purpose of this study was to evaluate the effect of 10 per cent maleic and 37 per cent phosphoric acid on the shear bond strength of Z100 composite resin with Scotchbond Multi-Purpose adhesive to primary and permanent tooth enamel. Four groups of 20 teeth each were established: 1, permanent teeth, 10 per cent maleic acid etched for 15 seconds; 2, permanent teeth, 10 per cent maleic acid etched for 30 seconds; 3, permanent teeth, 37 per cent phosphoric acid etched for 15 seconds; 4, primary teeth, 10 per cent maleic acid etched for 15 seconds. Five teeth from each group were randomly assigned for SEM examination of the etched enamel surface. Scotchbond Multi-Purpose primer and adhesive were applied to the etched enamel surface of the remaining 15 teeth and cured following the manufacturer's instructions. Z100 composite resin was placed in a nylon cylinder and cured for two 40 second intervals. Following thermocycling, the specimens were sheared on an universal testing machine and debonded areas were examined visually with a stereo microscope and with SEM. The mean shear bond strengths in MPa were: 1, 17.00; 2, 14.58; 3, 14.66; 4, 11.18. ANOVA and Student-Newman-Keuls analyses revealed no statistically significant difference among the groups. SEM examination showed the majority of specimens fractured at the adhesive-resin interface.

Acid Etching, Dental↗
PubMed2004

Improved wet bonding of methyl methacrylate-tri-n-butylborane resin to dentin etched with ten percent phosphoric acid in the presence of ferric ions.

The objective of this study was to determine the influence of dissolved dentinal substances in demineralized dentin on the hybridization of resin for bonding to dentin. It was hypothesized that these substances, including polyelectrolytes, significantly change the substrates, which could then be assessed by the addition of Na(+), Ca(2+), or Fe(3+) in 10% phosphoric acid. Bovine dentin specimens were etched for 10 s with a solution of 10% phosphoric acid (control) or of 22.0 mM dissolved sodium chloride (10P-Na), calcium chloride (10P-Ca), or ferric chloride (10P-Fe). The specimens were then rinsed, blot-dried, and primed three times with 5% 4-methacryloyloxyethyl trimellitate anhydride in acetone for 60 s. Methyl methacrylate-tri-n-butylborane resin was then applied. The tensile bond strength of each of the dumbbell-shaped specimens was then measured. The fractured surfaces and modified cross-sections were examined by scanning electron microscopy. The cross-sections were soaked in 6N HCl for 10 s and then in 1% sodium hypochlorite for 30 min to determine the resin content in the hybridized specimens. Shrinkage of the demineralized dentins upon drying was assessed by atomic force microscopy. The tensile bond strengths were 10.8 +/- 4.5 (control), 15.0 +/- 7.0 (10P-Na), 19.3 +/- 5.5 (10P-Ca), and 27.8 +/- 8.1 (10P-Fe) MPa. The atomic force microscopy studies showed that Fe(3+) minimized the shrinkage by drying for 10 s but Ca(2+) and Na(+) did not decrease the shrinkage the same as the control. The results support the hypothesis that the monomer permeability of wet demineralized dentin is effectively improved by dissolving ferric ions in the phosphoric acid, resulting in a greater bond strength and higher resin content in the hybridized dentin. The dissolved dentinal substances, including the polyelectrolytes, had a significant influence on the characteristics of the demineralized dentin, changing the degree of hybridization and bonding.

Animals↗
PubMed2005

Utilization of date stones for production of activated carbon using phosphoric acid.

Date stone wastes have been utilized for production of activated carbon by chemical activation with phosphoric acid using a fluidized-bed reactor. The effects of the activation time, activation temperature, impregnation ratio, and particle size on the yield and the adsorptive capacity towards iodine were studied. The yield and the quality of the activated carbon prepared by using H3PO4 were compared with that prepared from date stones using the same equipment, and under similar conditions by using ZnCl2 as an oxidizing agent. The maximum value of the iodine number of the activated carbon produced using H3PO4 in this work was about 495 under the following conditions: impregnation ratio 0.4, activation time 60 min, activation temperature 800 degrees C, particle size 0.60 mm. The iodine number for the produced activated carbon was higher when phosphoric acid was used, compared to that when zinc chloride was used as impregnation reagent; however, the yield obtained when H3PO4 was used was lower than the yield when ZnCl2 was used. The iodine number increases significantly with increasing the activation temperature. By increasing the impregnation ratio at the same temperature, the iodine number decreased sharply and an oscillation is noticed for all the cases but it was clearer at 800 degrees C. The average variation of the iodine number for the whole range of particle size used in this work is +/-10%.

Adsorption↗
PubMed1972

The oxidative dealkylation of insecticidal phosphoric acid triesters by mammalian liver enzymes.

1. The dealkylation of the insecticidal phosphoric acid triester, 2-chloro-1-(2,4-dichlorophenyl)vinyl diethyl phosphate, proceeds in mammalian liver slices via an oxidative mechanism and not by hydrolysis. 2. The enzyme that catalyses the reaction is located in the microsomal fraction of liver homogenate and is dependent for activity on molecular oxygen and NADPH. 3. There are large species differences between rat, mouse, rabbit and dog in the activity of the enzymes, the relative rates of dealkylation being 1, 8, 24 and 88 respectively in liver slices. 4. Dimethyl and di-isopropyl phosphate triesters are also dealkylated by rabbit liver microsomal preparations. 5. The mechanism of dealkylation involves hydroxylation at the alpha-carbon atom of an alkyl group, which is removed as the corresponding aldehyde, and is thus analogous to that of similar reactions catalysed by the microsomal mixed-function oxidases. 6. The relevance of these findings in the toxicology of phosphoric acid triesters is discussed.

Alkylation↗
PubMed1996

Effect of phosphoric acid concentration on wet-bonding to etched dentin.

OBJECTIVE: This study was conducted to investigate the influence of phosphoric acid (H3PO44) demineralization of dentin during smear layer removal prior to dentin bonding. METHODS: Bovine dentin was pre-treated with either 10 wt% or 35 wt% phosphoric acid for 30 s. Substrates were then rinsed and either kept moist or air-dried before a light-cured bonding system was applied. The adhesive system consisted of a 5 wt% 4-methacryloyloxyethyl trimellitate anhydride (4-META) in acetone primer, and a photocured bonding agent, 4-META/triethylene glycol dimethacrylate-camphorquinone/N-phenylglycine (4-META/TEGDMA-CQ/NPG). Tensile bond strengths of bonded specimens were measured, and specimens were examined with a scanning electron microscope (SEM). Data obtained were subjected to two-way ANOVA and Duncan's New Multiple Range test to examine statistically significant differences (p < 0.05). RESULTS: Improved tensile bond strengths were measured when the 4-META/acetone primer was applied to wet dentin that had been etched with 10 wt% H3PO4 compared with similarly etched but dry dentin samples. However, when the dentin was etched with 35 wt% H3PO4, there was no significant difference in tensile bond strength between wet and dry specimens. SEM examination of the fractured surfaces revealed a number of cohesive failures in the demineralized dentin. Microscopic examination of cross sections of these surfaces indicated that resin impregnation was inadequate and that the hybrid layers in the cohesively fractured specimens were defective. SIGNIFICANCE: Phenomena observed in this investigation suggest that the channels between the H3PO4-denatured collagen fibers were difficult to preserve, so adhesive monomer impregnation of these substrates was impaired in a considerable number of test specimens.

Acid Etching, Dental↗
PubMed2001

Experimental electron density of urea-phosphoric acid (1/1) at 100 K.

The deformation electron density of the urea-phosphoric acid adduct has been studied from 100 K X-ray and neutron diffraction experiments. Data were interpreted according to the Hirshfeld model. The long hydrogen bonds show characteristics of electrostatic interaction. Deformation density maps on the short hydrogen bond shows hydrogen more strongly bonded to urea than to phosphoric acid, and peak maxima at almost midway between the two O-H bonds.

Journal Article↗
PubMed2004

Manufacture of fermentable sugar solutions from sugar cane bagasse hydrolyzed with phosphoric acid at atmospheric pressure.

Sugar cane bagasse, a renewable and cheap bioresource, was hydrolyzed at 100 degrees C using phosphoric acid at different concentrations (2, 4, or 6%) and reaction times (0-300 min) to obtain fermentable sugar solutions, which have a high concentration of sugars (carbon source for microorganism growth) and a low concentration of growth inhibitors (acetic acid and furfural). Xylose, glucose, arabinose, acetic acid, and furfural were determined following the hydrolysis. Kinetic parameters of mathematical models for predicting these compounds in the hydrolysates were obtained. Derived parameters such as efficiency of hydrolysis or purity of hydrolysates were considered to select as optimal conditions 6% phosphoric acid at 100 degrees C for 300 min. Using these conditions, 21.4 g of sugars L(-)(1) and <4 g of inhibitors L(-)(1) were obtained from the hydrolysis with a water/solid ratio of 8 g of water g(-)(1) of sugar cane bagasse on a dry basis.

Atmospheric Pressure↗
PubMed2001

Phosphoric acid and copper (II) sulphate as a combined etchant and activator prior to the use of an anaerobic adhesive.

OBJECTIVES: Previous work has shown that steel attachments can be bonded to etched human enamel using anaerobic adhesives, following treatment with a solution of 0.05M copper (II) sulphate. The objectives of this experiment were to determine whether simultaneous etching and activation could be performed with a combined solution of o-phosphoric acid and copper (II) sulphate. METHOD: Stainless steel attachments were bonded to human enamel using an anaerobic adhesive. In each case the enamel was etched and activated using a solution of 37% o-phosphoric acid containing various concentrations of copper (II) sulphate. After bench curing for one hour, the specimens were shear bond tested to failure and the load at debond recorded in each case. Following determination of the optimum copper (II) sulphate concentration the experiment was repeated, but this time the acid was made into a gel using colloidal silica. The effect of rinse time after etching was also investigated with the gel. RESULTS: The results were analysed using mean force to debond (N) and 95% confidence intervals. Kaplan-Meier survival probabilities and log rank tests were also performed. Under the conditions of this experiment the optimum concentration of copper (II) sulphate was found to be 1M. When the acid was made into a gel the optimum rinsing time was found to be 60s. SIGNIFICANCE: This experiment demonstrates that steel attachments can be bonded to enamel using anaerobic adhesives where the enamel has been simultaneously etched and activated. A combined o-phosphoric acid and copper (II) sulphate solution or gel can be used, but a conventional etch pattern is not produced.

Acid Etching, Dental↗