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The aim of this study is to evaluate the color changes and the stability at a 1-year follow-up of white spot lesions (WSLs) treated with an infiltrating technique by using etching and TEGDMA resin. The color of 22 white spot lesions and the sound adjacent enamel (SAE) were assessed with a spectrophotometer at T0 (baseline), T1 (after treatment), and T2 (1 year after). The color change &Delta, E (WSLs-SAE) at T0 vs. T1 were compared to evaluate the camouflage effect efficiency, and at T1 vs. T2 to assess the stability of outcomes. To evaluate the effect on the treatment outcome of gender, the presence or not of previous orthodontic treatment, WSLs onset more/less than 10 years, the age of the patient, and the &Delta, E WSL (T0 vs. T1) was analyzed. The difference between &Delta, E (WSLs-SAE) at T0 and T1 resulted in statistical significance (p &lt, 0.01). No statistical difference was found between &Delta, E (WSLs-SAE) at T1 vs. T2. The variables considered showed no statistical differences in treatment outcomes. The results of our investigation show that the technique used is immediately effective and the camouflage effect keeps up and steady one year after treatment. Such results do not appear to be influenced by analyzed clinical variables.

This case report describes and analyses a tooth fragment reattachment technique used to resolve crown fractures of the anterior teeth. This treatment allows a conservative approach to traumatic coronal lesions offering a better possibility of maintaining aesthetics and function. The authors have illustrated here a clinical case of a fractured incisor. This case is characterized by several traumas on the same tooth that required different therapeutic solutions. We used an easy and ultra-conservative technique without any tooth preparation in the first and third traumatic injuries. In the second trauma, a direct restoration of the fractured tooth was performed. The adhesive reattachment is a simple system to achieve good aesthetic and functional results.Our clinical experiences demonstrated that, when tooth and fragment margins are intact, the reattachment technique without any tooth preparation is a simple and predictable procedure. Quality of adhesion is shown by the retention of the reattached fragment in the second trauma that caused only partial enamel fractures.

The anaerobic, anaerobic/aerobic (anaerobic followed by aerobic) and straight aerobic treatments of a simulated metal-cutting-fluid wastewater were evaluated in terms of the removal of organic nitrogen (primarily alkanolamines and heterocyclic compounds) and fatty acids, the two major constituents of many water-based metal-cutting fluids. The organic nitrogen was not well adsorbed on activated carbon but was degraded through the anaerobic/aerobic or straight aerobic treatment. It was also found that an acclimation period was necessary before the organic nitrogen could be anaerobically degraded. 2-Methylhexanoic, heptanoic, 3,5,5-trimethylhexanoic and benzoic acid, which were found in the wastewater, were degraded well both anaerobically and aerobically. The wastewater also contained a group of unidentified organic compounds that consisted of five gas chromatographic peaks (probably branched C 8 –C 10 fatty acids or their esters). These unidentified organics were partially degraded and persisted in the effluents, contributing to the non-biodegradable portion of organics. Several low molecular weight fatty acids (acetic acid, propanoic acid, 2-methylpropanoic acid, butanoic acid, 3-methylbutanoic acid and pentanoic acid) were produced during the periods when the influent chemical oxygen demand (COD) loading was varied to study the response of an anaerobic reactor to the variation. The anaerobic/aerobic treatment produced an effluent similar to that of the straight aerobic treatment with respect to fatty acid concentrations.

Exhaust and evaporative emissions tests were conducted on several methanol- and gasoline-fueled vehicles. Separate samples for chromatographlc analysis of formaldehyde, methanol, and Individual hydrocarbons were collected in each of the three phases of the driving cycle and in each of the two portions of the evaporative emissions test. One vehicle, equipped with an experimental variable-fuel engine, was tested using methanol/gasoline fuel mixtures of 100, 85, 50,15, and 0 percent methanol. Combustion-generated hydrocarbons were lowest using methanol fuel, and increased several-fold as the gasoline fraction was increased. Gasoline components In the exhaust Increased from zero as the gasoline fraction of the fuel was Increased. On the other hand, formaldehyde emissions were several times higher using methanol fuel than they were using gasoline. A dedicated methanol car and the variable-fuel car gave similar emissions patterns when they both were tested using methanol fuel. The organic-carbon composition of ...

A method was developed for determining individual hydrocarbon (HC) emissions from gasoline-, methanol- and variable-fueled vehicles. The exhaust samples are collected in Tedlar ® bags, and a portion of the sample is injected into a gas chromatograph, equipped with a DB-1 60 m × 0.32 mm I.D. (1.0 μm) fused-silica column. Methanol was well resolved from the gasoline HC species and did not interfere in the analysis. Validation, stability and intercomparison studies for total HC are also reported in this paper. In addition, an impinger—gas chromatography (GC) technique for determining unburned methanol emissions is also described. The detection limits of the GC methods for individual HCs and methanol was about 50 and 250 parts per billion (10 9 ) C, respectively. This corresponds to a vehicular mass emission rate of 0.1 mg/mile HC and 1.3 mg/mile methanol, respectively, for the Federal Test Procedure emissions test.

An analytical method for the determination of hydrocarbon and ether emissions from gasoline-, methanol-, and flexible-fueled vehicles is described. This method was used in Phase I of the Auto/Oil Air Quality Improvement Research Program to provide emissions data for various vehicles using individual reformulated gasolines and alternate fuels. These data would then be used for air modeling studies. Emission samples for tailpipe, evaporative, and running loss were collected in Tedlar bags. Gas chromatographic analysis of the emissions samples included 140 components (hydrocarbons, ethers, alcohols and aldehydes) between C1 and C12 in a single analysis of 54-minutes duration. Standardization, quality control procedures, and inter-laboratory comparisons developed and completed as part of this program are also described. (Copyright (c) 1992 Society of Automotive Engineers, Inc.).

The composition of dew collected from a Teflon surface was compared to summer rainwater concentrations at a site in Warren, MI. This comparison showed that natural dew is similar to rainwater with the exception that dew has much higher concentrations of Ca 2+ and Cl − and much lower acidity. Dry deposition rates of several species were measured to artificially-generated dew and a dry surface. It was found that deposition rates were 2–20 times greater to the artificial dew than to the dry surface, indicating that the presence of dew enhances both the retention of dry deposited particles and the absorption of water soluble gases. Measurement of the atmospheric concentrations of the depositing gases permitted the calculation of deposition velocities for particulate Cl − , NO − 3 , SO 2− 4 , Ca 2+ , Mg 2+ , Na + , K + and NH + 4 . Deposition velocities for gaseous HNO 3 , HCl, SO 2 and NH 3 were also determined after correction for particle deposition. These results indicate that acid dew is not a problem at this site. However, the ability of dew to increase the deposition rates of acids and acid precursors to some surfaces suggests that dew may be more acidic at sites with lower deposition rates of basic particles.

Le derive de la formaldehyde forme avec la phenylhydrazine (dinitro-«2,4») est elue et analyse par chromatographie en phase liquide a haute performance. Limite de detration: 1,0 ppb de HCHO pour 100 l d'air

Aldehyde emissions from wood-burning fireplaces were measured. Total aldehydes ranged from 0.6 to 2.3 g/kg of wood burned based on tests with cedar, jack pine, red oak, and ash. Formaldehyde, acetaldehyde, and p-tolualdehyde were the major aldehydes emitted with formaldehyde comprising 21-42% of the total. Aldehyde and particle emissions were inversely correlated with burn rate and may also be related to wood type. On the basis of our measurements, nationwide aldehyde emissions from residental wood burning were estimated to be between 14 and 54 Gg/year. This value is comparable to both power plant and automobile aldehyde emission sources. It is likely that residental wood burning is a major source of primary aldehydes during the winter. 20 references.

A new ambient NO/sub 2/ sorbent method was developed based on quantitative collection of NO/sub 2/ in a cartridge containing Florisll coated with diphenylamine (DPA). The NO/sub 2/ reacts with DPA to form 4-nitro-, 2-nitro-, and N-nitroso-DPA derivatives. The NO/sub 2/ products are eluted from the cartridge, analyzed by high-performance liquid chromatography with UV detection, and related to the amount of NO/sub 2/ in the sampled air. This novel approach utilizes commercially available Thermosorb/F air sampling cartridges packed with Florisil as the sorbent. No interferences from NO, O/sub 3/, HNO/sub 3/, SO/sub 2/, and humidity were found, but PAN produced a 50% positive interference in the method. The detection limit is 0.1 ppb NO/sub 2/ for a 2000-L air sample which corresponds to an 8-h sampling period at 4.0 L/min. The cartridges were used to monitor daily ambient NO/sub 2/ levels ranging from 1.8 to 33.5 ppb NO/sub 2/ and indoor NO/sub 2/ levels ranging from 2.0 to 144.8 ppb NO/sub 2/.

A new method for determining the hydroxymethane-sulfonate ion (HMSA) in wet deposition was developed by measuring the total and free formaldehyde content of the sample. Total formaldehyde (HCHO) is measured by dissociating the HMSA into formaldehyde and bisulfite with a strong base and reacting the formaldehyde with 2,4-dinitrophenylhydrazine (DNPH). The formaldehyde-DNPH derivative formed is then determined by high-performance liquid chromatography. Free formaldehyde is similarly determined in another aliquot, but without the addition of the base. The difference between the total and free HCHO measurements gives the bound HCHO or HMSA content of the sample. The method was linear for HMSA concentrations ranging from 0.06 to 6.3 ..mu..g/mL. Recovery of HCHO from the dissociated HMSA ranged from 90 to 95%. The detection limit of the method on the basis of a signal to blank ratio of 3 was 0.01 ..mu..g/mL. The method was used to measure HMSA in rain and snow samples. 14 references, 3 figures, 2 tables.

An improved, simple and rapid method for the determination of formaldehyde and other aldehydes in automobile exhaust was developed. Sample collection and derivatization are performed directly in a midget impinger containing an acetonitrile solution of 2,4-dimitrophenylhydrazine and catalyst. This scheme eliminates the time-consuming and lengthy recovery steps required in other procedures and allows direct injection of an aliquot of the sample into a high-performance liquid chromatograph for analysis. Detection limits for formaldehyde, acetaldehyde, acrolein and benzaldehyde are 20, 10, 5 and 4 ppb*, respectively, for a 20-l exhaust sample. The analysis time is as short as 10 min if only formaldehyde and acetaldehyde are of interest. The technique was used to measure aldehyde emissions from ethanol-, gasoline- and diesel-fueled vehicles.

A sensitive, uncomplicated, and rapid method for the determination of formaldehyde and other aldehydes has been developed. The method is based on the reaction of the aldehyde species with 2-diphenylacetyl-1,3-indandione-1-hydrazone to form fluorescent azine derivatives. The fluorescence excitation and emission spectra have been obtained for several derivatives. The method developed eliminates the lengthy recovery steps required in other methods by performing the sample collection and derivatization directly in midget impingers containing an acetonitrile solution of the reagent. High performance liquid chromatography with fluorescence detection is used to separate and quantitate the individual aldehydes. The detection limits for formaldehyde, acetaldehyde, acrolein, and benzaldehyde are 6 ppb, 4.5 ppb, 0.6 pb, and 0.15 ppb, respectively, in the exhaust gas. The analysis time for the method is about 10 minutes if only one or two aldehydes are of interest. This technique has been used to measure ald...

Aldehyde and unburned fuel emissions (UBF) were measured from experimental 6V-92TA and 6V-71N methanol-fueled heavy-duty diesel engines. The 6V-71N engine was tested with experimental oxidation catalytic converters. Formaldehyde accounted for 97-99% of the total aldehydes emitted from both engines. Aldehyde and unburned fuel concentrations were highest in the idle modes of the 13-mode test and decreased with increasing engine speed and load. The 13-mode weighted aldehyde and UBF emissions for the 6V-92TA engine were 0.10 G/BHP-HR and 2.01 G/BHP-HR, respectively. The 13-mode aldehyde and UBF emissions from the 6V-71N engine before catalytic treatment were 0.32 G/BHP-HR and 4.51 G/BHP-HR, respectively. These emissions were reduced to 0.19 G/BHP-HR and 1.10 G/BHP-HR with catalytic treatment. Total aldehyde emissions from the methanol-fueled engines compared favorably with the 0.07 to 0.28 G/BHP-HR range reported for heavy-duty conventionally fueld diesel engines. Formaldehyde emissions from these engines were higher than those of conventionally fueled diesel engines but similar to those of other methanol-fueled diesel engines. Particulate and NO/subX/ emissions from these engines were very low and ranged from 0.02-0.22 G/BHP-HR and 1.45-1.66 G/BHP-HR, respectively. These engines show promise for meeting the 1991 urban bus 0.10 G/BHP-HR particulate standard.