Comparison of Load-Bearing Capacities of 3-Unit Fiber-Reinforced Composite Adhesive Bridges with Different Framework Designs.

BACKGROUND The aim of this study was to investigate and compare the load-bearing capacities of three-unit direct resin-bonded fiber-reinforced composite fixed dental prosthesis with different framework designs. MATERIAL AND METHODS Sixty mandibular premolar and molar teeth without caries were collected and direct glass fiber-resin fixed FDPs were divided into 6 groups (n=10). Each group was restored via direct technique with different designs. In Group 1, the inlay-retained bridges formed 2 unidirectional FRC frameworks and pontic-reinforced transversal FRC. In Group 2, the inlay-retained bridges were supported by unidirectional lingual and occlusal FRC frameworks. Group 3, had buccal and lingual unidirectional FRC frameworks without the inlay cavities. Group 4 had reinforced inlay cavities and buccal-lingual FRC with unidirectional FRC frameworks. Group 5, had a circular form of fiber reinforcement around cusps in addition to buccal-lingual FRC frameworks. Group 6 had a circular form of fiber reinforcement around cusps with 2 bidirectional FRC frameworks into inlay cavities. All groups were loaded until final fracture using a universal testing machine at a crosshead speed of 1 mm/min. RESULTS Mean values of the groups were determined with ANOVA and Tukey HSD. When all data were evaluated, Group 6 had the highest load-bearing capacities and revealed significant differences from Group 3 and Group 4. Group 6 had the highest strain (p>0.05). When the fracture patterns were investigated, Group 6 had the durability to sustain fracture propagation within the restoration. CONCLUSIONS The efficiency of fiber reinforcement of the restorations alters not only the amount of fiber, but also the design of the restoration with fibers.

The lead content of currently available new residential paint in several Asian countries.

Worldwide prohibitions on lead gasoline additives were a major international public health accomplishment, the results of which are still being documented in parts of the world. Although the need to remove lead from paints has been recognized for over a century, evidence reported in this article indicates that lead-based paints for household use, some containing more than 10% lead, are readily available for purchase in some of the largest countries in the world. Sixty-six percent of new paint samples from China, India, and Malaysia were found to contain 5000 ppm (0.5%) or more of lead, the US definition of lead-based paint in existing housing, and 78% contained 600 ppm (0.06%) or more, the limit for new paints. In contrast, the comparable levels in a nearby developed country, Singapore, were 0% and 9%. In examining lead levels in paints of the same brands purchased in different countries, it was found that some brands had lead-based paints in one of the countries and paints meeting US limits in another; another had lead-free paint available in all countries where samples were obtained. Lead-based paints have already poisoned millions of children and likely will cause similar damage in the future as paint use increases as countries in Asia and elsewhere continue their rapid development. The ready availability of lead-based paints documented in this article provides stark evidence of the urgent need for efforts to accomplish an effective worldwide ban on the use of lead in paint.

Síndrome opsoclono-mioclono parainfeccioso secundario a virus varicela-zóster / Parainfectious opsoclonus-myoclonus syndrome secondary to varicella-zoster virus infection

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[Cost effectiveness of the diagnostic study of dementia in an extra-hospital Neurology service]. / Rentabilidad del estudio diagnóstico de la demencia en una consulta extrahospitalaria de Neurología.

AIM: The purpose of this study was to analyse the cost effectiveness of the complementary tests in the diagnosis of reversible causes of dementia in an extra-hospital Neurology service. PATIENTS AND METHODS: Patients referred to the Neurology service from Primary Care with a diagnosis of dementia according to DSM-III-R criteria. The following routine complementary tests were performed: 1. Analyses, including blood count, biochemical study, vitamin B12 and folic levels, thyroid hormones, and syphilis serodiagnosis; 2. Neuroimaging study, consisting in computerised axial tomography or cranial magnetic resonance. RESULTS: A total of 269 consecutive patients diagnosed as suffering from dementia were included in the study. The mean age of the patients was 74.5 years (49-94 years) and 61% were females. The most frequent cause of dementia was Alzheimer's disease (79.9%). In all, 31 patients presented potentially reversible conditions (11.5%), but if we exclude depression, the dementia was only reversible in one patient (0.4%). CONCLUSIONS: The percentage of patients with reversible causes of dementia in the field of extra-hospital neurology is low. The diagnostic study must be individualised according to the clinical suspicion.

Rentabilidad del estudio diagnóstico de la demencia en una consulta extrahospitalaria de Neurología / Cost effectiveness of the diagnostic study of dementia in an extra-hospital neurology service

Objetivo. Analizar la rentabilidad de las pruebas complementarias en el diagnóstico de causas reversibles de demencia en una consulta extrahospitalaria de Neurología. Pacientes y métodos. Pacientes remitidos a la consulta de Neurología desde Atención Primaria con el diagnóstico de demencia según los criterios del DSM-III-R. Se realizaron las siguientes pruebas complementarias de manera rutinaria: 1. Analítica, que incluía hemograma, estudio bioquímico, concentración de vitamina B12 y ácido fólico, hormonas tiroideas y serología para sífilis; 2. Estudio de neuroimagen, consistente en tomografía axial computarizada o resonancia magnética craneal. Resultados. Se incluyó un total de 269 pacientes consecutivos diagnosticados de demencia. La edad media de los pacientes fue de 74,5 años (49-94 años) y el 61 por ciento era mujer. La causa más frecuente de demencia fue la enfermedad de Alzheimer (79,9 por ciento). Un total de 31 pacientes presentaba patologías potencialmente reversibles (11,5 por ciento); pero, si exceptuamos la depresión, la demencia fue reversible únicamente en un paciente (0,4 por ciento). Conclusiones. La proporción de pacientes con causas reversibles de demencia en el ámbito neurológico extrahospitalario es baja. El estudio diagnóstico debe individualizarse en función de la sospecha clínica (AU)

Aim. The purpose of this study was to analyse the cost effectiveness of the complementary tests in the diagnosis of reversible causes of dementia in an extra-hospital Neurology service. Patients and methods. Patients referred to the Neurology service from Primary Care with a diagnosis of dementia according to DSM-III-R criteria. The following routine complementary tests were performed: 1. Analyses, including blood count, biochemical study, vitamin B12 and folic levels, thyroid hormones, and syphilis serodiagnosis; 2. Neuroimaging study, consisting in computerised axial tomography or cranial magnetic resonance. Results. A total of 269 consecutive patients diagnosed as suffering from dementia were included in the study. The mean age of the patients was 74.5 years (49-94 years) and 61% were females. The most frequent cause of dementia was Alzheimer’s disease (79.9%). In all, 31 patients presented potentially reversible conditions (11.5%), but if we exclude depression, the dementia was only reversible in one patient (0.4%). Conclusions. The percentage of patients with reversible causes of dementia in the field of extra-hospital neurology is low. The diagnostic study must be individualised according to the clinical suspicion (AU)

Evaluation of a portable X-ray fluorescence instrument for the determination of lead in workplace air samples.

Occupational Safety and Health Administration (OSHA) regulations for worker exposure to lead specify worker protection levels based upon airborne concentrations of lead dust. The rapid, on-site determination of lead in air filter samples using a portable x-ray fluorescence (XRF) instrument with an attachment to hold the filter would expedite the exposure assessment process and facilitate compliance with the OSHA standards. A total of 65 lead in air filter samples were collected at bridge blasting lead-abatement projects using closed-faced, 37-mm cassettes with pre-loaded 0.8 micron pore size mixed cellulose ester membrane filters. The lead loading range of the data set was 0.1-1514.6 micrograms (micrograms) of lead/sample. Samples were initially analyzed with a field portable XRF (NITON 700) using an experimental non-destructive XRF method. Samples were subsequently analyzed using National Institute for Occupational Safety and Health (NIOSH) Method 7105 (Graphite Furnace AA) as a reference analytical method. The paired data were not normally distributed; therefore, the non-parametric Wilcoxon signed rank test was used for statistical analysis. There was no statistically significant difference between data from the field portable XRF method and the NIOSH method (p-value = 0.72). Linear regression of the data resulted in a slope of 0.959, a y-intercept of 5.20 micrograms, and an r2 of 0.985. The XRF limit of detection and limit of quantitation were determined to be 6.2 and 17 micrograms of lead/sample, respectively. The XRF method accuracy was +/- 16.4% (7.1%-27%, 90% confidence interval). The data presented in this study indicate that field-portable XRF can be used for the analysis of lead air filter samples over the range of 17 to 1500 micrograms of lead/sample. The practicing industrial hygienist can use field-portable XRF to produce a rapid, on-site determination of lead exposure that can immediately be communicated to workers and help identify appropriate levels of personal protection. As the method is non-destructive, samples can subsequently be sent to a laboratory for confirmation. Confirmation would be recommended when greater than 16.4 percent accuracy from an analytical method is required. This study provided data of suitable quality for the development of NIOSH Method 7702, "Lead by Field Portable XRF."

Use of a field portable X-Ray fluorescence analyzer to determine the concentration of lead and other metals in soil samples.

Field portable methods are often needed in risk characterization, assessment and management to rapidly determine metal concentrations in environmental samples. Examples are for determining: "hot spots" of soil contamination, whether dust wipe lead levels meet housing occupancy standards, and worker respiratory protection levels. For over 30 years portable X-Ray Fluorescence (XRF) analyzers have been available for the in situ, non-destructive, measurement of lead in paint. Recent advances made possible their use for analysis of airborne dust filter samples, soil, and dust wipes. Research at the University of Cincinnati with the NITON 700 Series XRF instrument (40 millicurie Cadmium 109 source, L X-Rays) demonstrated its proficiency on air sample filters (NIOSH Method No. 7702, "Lead by Field Portable XRF; limit of detection 6 microg per sample; working range 17-1,500 microg/m3 air). Research with lead dust wipe samples from housing has also shown promising results. This XRF instrument was used in 1997 in Poland on copper smelter area soil samples with the cooperation of the Wroclaw Medical Academy and the Foundation for the Children from the Copper Basin (Legnica). Geometric mean soil lead concentrations were 200 ppm with the portable XRF, 201 ppm with laboratory-based XRF (Kevex) and 190 ppm using atomic absorption (AA). Correlations of field portable XRF and AA results were excellent for samples sieved to less than 125 micrometers with R-squared values of 0.997, 0.957, and 0.976 for lead, copper and zinc respectively. Similarly, correlations were excellent for soil sieved to less than 250 micrometers, where R-squared values were 0. 924, 0.973, and 0.937 for lead, copper and zinc, respectively. The field portable XRF instrument appears to be useful for the determination of soil pollution by these metals in industrial regions.

High concentrations of heavy metals in neighborhoods near ore smelters in northern Mexico.

In developing countries, rapid industrialization without environmental controls has resulted in heavy metal contamination of communities. We hypothesized that residential neighborhoods located near ore industries in three northern Mexican cities would be heavily polluted with multiple contaminants (arsenic, cadmium, and lead) and that these sites would be point sources for the heavy metals. To evaluate these hypotheses, we obtained samples of roadside surface dust from residential neighborhoods within 2 m of metal smelters [Torreón (n = 19)] and Chihuahua (n = 19)] and a metal refinery [Monterrey (n = 23)]. Heavy metal concentrations in dust were mapped with respect to distance from the industrial sites. Correlation between dust metal concentration and distance was estimated with least-squares regression using log-transformed data. Median dust arsenic, cadmium, and lead concentrations were 32, 10, and 277 microg/g, respectively, in Chihuahua; 42, 2, and 467 microg/g, respectively, in Monterrey, and 113, 112, and 2,448 microg/g, respectively, in Torreón. Dust concentrations of all heavy metals were significantly higher around the active smelter in Torreón, where more than 90% of samples exceeded Superfund cleanup goals. At all sites, dust concentrations were inversely related to distance from the industrial source, implicating these industries as the likely source of the contamination. We concluded that residential neighborhoods around metal smelting and refining sites in these three cities are contaminated by heavy metals at concentrations likely to pose a health threat to people living nearby. Evaluations of human exposure near these sites should be conducted. Because multiple heavy metal pollutants may exist near smelter sites, researchers should avoid attributing toxicity to one heavy metal unless others have been measured and shown not to coexist.

Urinary arsenic excretion as a biomarker of arsenic exposure in children.

Urinary arsenic concentration has been used generally for the determination of exposure, but much concern has been raised over the most appropriate expression for urinary arsenic levels. In this study, we examined the influence of various adjustments of expressing urinary arsenic data. All children who were less than 72 mo of age and who were potty trained were invited to participate in the present study. Urine, soil, and dust samples were collected, and arsenic measurements were made. The geometric mean of speciated urinary arsenic among children who provided first-voided urine samples on 2 consecutive mornings was 8.6 microg/l (geometric standard deviation = 1.7, n = 289). Speciated urinary arsenic was related significantly to soil arsenic in bare areas (p < .0005). Use of a single urine sample versus the average of two first-voided urine samples collected on 2 consecutive mornings did not significantly alter the relationship between environmental arsenic and urinary arsenic levels. Furthermore, none of the adjustments to urinary concentration improved the strength of correlation between urinary arsenic and soil arsenic levels. Concentration adjustments may not be necessary for urinary arsenic levels obtained from young children who provide first-void samples in the morning.

Environmental arsenic exposure of children around a former copper smelter site.

Arsenic residues in the communities surrounding former smelters remain a public health concern, especially for infants and children. To evaluate environmental exposure among these children, a population-based cross-sectional study was conducted in the vicinity of a former copper smelter in Anaconda, Montana. A total of 414 children less than 72 months old were recruited. First morning voided urine samples and environmental samples were collected for arsenic measurements. The geometric mean of speciated urinary arsenic was 8.6 microg/liter (GSD = 1.7, N = 289). Average arsenic levels of different types of soil ranged from 121 to 236 microg/g and were significantly related to proximity and wind direction to the smelter site. The same significant relationship was observed for interior dust arsenic. Speciated urinary arsenic was found to be significantly related to soil arsenic in bare areas in residential yards (P < 0.0005). In general, elevated excretion of arsenic was demonstrable and warranted parents' attention to reduce exposure of their children to environmental arsenic.

Disparities in clinical laboratory performance for blood lead analysis.

OBJECTIVE: To evaluate the validity of blood lead analysis for clinical specimens. DESIGN: We submitted blood lead samples with a known lead concentration, in a blinded fashion, as clinical specimens to 18 laboratories. These laboratories were surveyed for the following characteristics that were hypothesized to be related to assay validity: laboratory ownership (state vs private), participation in the Centers for Disease Control Blood Lead Proficiency Program, assay method, and price. Each laboratory received 6 specimens with an actual blood lead (ABPb) concentration of 0.43 mumol/L (9 micrograms/dL) and 3 additional specimens--each with an ABPb concentration of 0.33, 0.89, and 1.59 mumol/L (6.9, 18.4, and 32.9 micrograms/dL, respectively). OUTCOME MEASURES: Misclassification error rates for reporting an elevation ( > or = 0.48 mumol/L [ > or = 10 micrograms/dL) in the blood lead concentration, the within-laboratory mean and coefficient of variation (CV) (for multiple specimens with an ABPb concentration of 0.43 mumol/L [9 micrograms/dL]), and the adjusted odds of a reported blood lead concentration differing from those of an ABPb concentration by more than 0.14 mumol/L (3 micrograms/dL). RESULTS: Blood lead results were obtained for 157 of 162 submissions. One laboratory reported all blood lead specimens as "below 0.48 mumol/L (10 micrograms/dL)." Two (11%) of 18 specimens with an ABPb concentration of 0.89 mumol/L (18.4 micrograms/dL) and 1 (6%) of 17 with an ABPb concentration of 1.59 mumol/L (32.9 micrograms/dL) were classified as below 0.48 mumol/L (10 micrograms/dL); 2 (11%) of 18 with an ABPb concentration of 0.33 mumol/L (6.9 micrograms/dL) and 44 (42%) of 104 with an ABPb concentration of 0.43 mumol/L (9 micrograms/dL) were classified as 0.48 mumol/L or greater ( > or = 10 micrograms/dL). For specimens with an ABPb concentration of 0.43 mumol/L (9 micrograms/dL), the within-laboratory mean ranged from 0.23 to 0.52 mumol/L (4.8-10.7 micrograms/dL); the CV ranged from 3% to 37%. Laboratories that used anodic stripping voltammetry were 6.3 (95% confidence interval, 1.4-28.6) times more likely to report a specimen that differed from the ABPb concentration by more than 0.14 mumol/L (3 micrograms/dL) than those that used atomic absorption methods. No other laboratory characteristic predicted discordance between the reported blood lead and ABPb concentrations. CONCLUSIONS: This study documents wide variation in the validity of the blood lead measurement among clinical laboratories. While the performance of some laboratories far exceeded the criteria of the Centers for Disease Control Blood Lead Proficiency Program, others made large errors that could have resulted in the false-negative misclassification of children with significant lead exposure. Given these differences, the purchasers of laboratory services may require access to laboratory proficiency data to make rational choices among clinical laboratories. Further study of laboratory performance on clinical specimens is required to determine if order-of-magnitude errors occur with sufficient frequency to warrant routine submission of blinded quality control specimens by proficiency programs and to determine the cause of the poor performance of laboratories that used the anodic stripping voltammetry methodology.

The relationship between surface dust lead loadings on carpets and the blood lead of young children.

The final clean-up of residential lead abatement projects in federally-supported housing, as well as in other housing in a number of states, must meet surface dust lead clearance levels expressed as µg of lead per square foot. These clearance levels were established because hand-to-mouth ingestion of lead-contaminated dust is recognised as a major pathway through which many children are exposed. A dilemma exists because many floors in housing undergoing abatement are carpeted and the established clearance levels are generally not recommended for use on carpets. These clearance levels are also used as 'action levels' to determine whether exposure reduction activities are needed. The US Environmental Protection Agency is currently in the process of issuing standards for hazardous levels of lead in interior dust and bare soil under Title X of the Housing and Community Development Act of 1992, 'The Residential Lead-Based Paint Hazard Reduction Act of 1992'. An effort to develop a potential surface dust lead clearance level for carpets was made using an existing vacuum dust collection method that has previously been shown to be a reliable indicator of childhood lead exposure. This method was designed for use on carpeted and non-carpeted surfaces. Using data from the Cincinnati Soil Lead Abatement Demonstration Project, the suggested floor-dust lead level where an estimated 95% of the population of children would be expected to have blood lead values below the national goal of 10 µg dL(-1), was more than an order of magnitude lower than the current floor-dust lead clearance level of 1080 µg m(-2) (100 µg ft(-2)). Further comparisons of blood lead and carpet lead levels in other parts of the country should be performed before a risk-based lead loading clearance level is established.

Anodic stripping voltammetry procedure modified for improved accuracy of blood lead analysis.

In evaluating the accuracy and reliability of blood lead (PbB) measurements with the Environmental Science Associates Model 3010A Trace Metal Analyzer, intralaboratory comparison demonstrated that use of the operating conditions recommended by the manufacturer resulted in consistently underestimated PbB concentrations less than 400 micrograms/L and overestimated PbB values greater than 400 micrograms/L. At PbB concentrations less than 50 micrograms/L, measured concentrations were often registered as negative results. However, these negative values could be replicated to within +/- 10 micrograms/L, indicating good precision of the method, but obviously not good accuracy. In addition, lower-than-expected lead (Pb) values were measured in samples containing increased concentrations of copper (Cu), such as may occur in pregnant women. We modified the procedure to eliminate these inaccuracies by substituting manual peak-height measurements for reliance on the integrator and digital display of the instrument. We established the accuracy of the modified procedure by using calibration standards previously quantified by isotope dilution-mass spectroscopy. A quality-control program for monitoring PbB analysis is also described.

The relationship of biological indices of lead exposure to the health status of workers in a secondary lead smelter.

The fidelity with which common indices of lead exposure correlate with renal and hematopoietic function and with frequency of symptoms was studied. The subjects were men working in a secondary lead smelter. Among several indices of renal function, only serum urea nitrogen (SUN) was consistently correlated with any of the indices of lead exposure. The concentration of lead in blood(PbB), the rate of urinary excretion of lead (PbU) and of alpha aminolevulinic acid in the urine (ALAU) correlated with SUN. By contrast, erythrocytic porphyrin concentration (EP) did not correlate with SUN. Similarly, the frequency of occurrence of symptoms correlated well with PbB and ALAU but did not correlate with EP. All of the above indices of lead exposure, with the exception of PbU, correlated well with hemoglobin (Hb) status. In summary, these results suggest that PbB rather than EP is the best single exposure index for biological monitoring of lead workers. This measurement should be supplemented by peiodic determination of SUN and Hb.