Compressive strength and setting time determination of glass-ionomer cements incorporated with cetylpyridinium chloride and benzalkonium chloride.

Because of the relatively frequent occurrence of recurrent caries after a restorative treatment, and because of the huge number of cariogenic microorganisms present in the oral cavity, which present a potential risk factor regarding the development of new carious lesions, attention has increasingly been directed towards the therapeutic antimicrobial effects of restorative materials. The glass ionomer cements distinguish themselves as the most acceptable restorative materials possessing the positive characteristics of fluorine in the processes of remineralisation and antimicrobial action. In addition to the release of fluoride ions, GICs can potentially be used as templates for the release of other active antimicrobial components. The addition of antimicrobial compounds in the glass ionomer cements and analysis of their physical characteristics are very important especially for use in the posterior region of milk teeth. The aim of this study was to analyse the physical characteristics of ChemFlex and Fuji IX, conventional glass ionomer cements incorporated with the antimicrobial components Cetylpyridinium Chloride and Benzalkonium Chloride, through measurements of their setting times, and determination of their compressive strengths. Five samples of each glass ionomer with no antimicrobial compounds added were prepared--to serve as a control group; and collections of five samples of each cement with different concentrations of Cetylpyridinium Chloride and Benzalkonium Chloride--1%, 2% and 3%--added to them were also prepared--a total of 60 samples. The results of the analysis point out that it is possible to incorporate these antimicrobial agents in conventional GICs, and this is especially true when the added amount of the antimicrobial agents is 1%.

The potential of fluoride-releasing dental restoratives to inhibit enamel demineralization: an SEM study.

UNLABELLED: (Full text is available at http://www.manu.edu.mk/prilozi). OBJECTIVES: The study was aimed at determining the effectiveness of fluoride-releasing materials (conventional and resin-modified glass-ionomers, compomer and fluoride-releasing composite resin) in inhibiting demineralization of restored teeth in an artificial caries medium. METHODS: A total of 72 teeth (36 deciduous and 36 permanent) were used and Class V cavities were prepared on each tooth. These cavities were restored with or without conditioning (except for the composite, where all specimens were conditioned). The teeth were then stored in artificial saliva for periods of 1, 6, 12 and 18 months before being exposed to an acidic artificial caries gel and examined by SEM. RESULTS: In the absence of a restoration, teeth were found to undergo enamel demineralization. Conventional glass-ionomer cements were found to inhibit this significantly. The resin-modified glass-ionomer generally had little effect, except for the18 month specimens, which also showed distinct zones of inhibition. The compomer showed no inhibition, and the fluoride-releasing composite resin showed only limited signs of inhibition. CONCLUSIONS: Glass-ionomers, both conventional or resin-modified, are more effective at protecting the tooth against further decay than either compomers or fluoride-releasing composites, with the best protection of all being provided by conventional glass-ionomers. The nature of the tooth had no influence on these outcomes. Key words: Dental restoratives, artificial caries, electron microscopy, fluoride release.

Case-control study of radon and lung cancer in New Jersey.

Radon is known to cause lung cancer in humans; however, there remain uncertainties about the effects associated with residential exposures. This case-control study of residential radon and lung cancer was conducted in five counties in New Jersey and involved 561 cases and 740 controls. A year long alpha-track detector measurement of radon was completed for approximately 93% of all residences lived in at the time of interview (a total of 2,063). While the odds ratios (ORs) for whole data were suggestive of an increased risk for exposures >75 Bq m(-3), these associations were not statistically significant. The adjusted excess OR (EOR) per 100 Bq m(-3) was -0.13 (95% CI: -0.30 to 0.44) for males, 0.29 (95% CI: -0.12 to 1.70) for females and 0.05 (95% CI: -0.14 to 0.56) for all subjects combined. An analysis of radon effects by histological type of lung cancer showed that the OR was strongest for small/oat cell carcinomas in both males and females. There was no statistical heterogeneity of radon effects by demographic factors (age at disease occurrence, education level and type of respondent). Analysis by categories of smoking status, frequency or duration did not modify the risk estimates of radon on lung cancer. The findings of this study are consistent with an earlier population-based study of radon and lung cancer among New Jersey women, and with the North American pooling of case control radon seven studies, including the previous New Jersey study. Several uncertainties regarding radon measurements and assumptions of exposure history may have resulted in underestimation of a true exposure-response relationship.

Contained myocardial rupture: a variant linking complete and incomplete rupture.

Myocardial rupture is an uncommon complication of myocardial infarction, often with devastating haemodynamic consequences. Although rupture is usually fatal, when patients do survive, the majority present with a pseudoaneurysm in which the rupture is sealed by a haematoma on the epicardial surface of the heart. Cases in which all myocardial layers are dissected except the epicardium or visceral pericardium have been included under this subheading. The authors describe such a case and suggest the pathological description of a "contained myocardial rupture". This link between complete and incomplete myocardial rupture may allow a more conservative management approach to be pursued.

Bradycardic syncope in 2 patients who recently began gatifloxacin treatment.

Gatifloxacin is a synthetic broad-spectrum 8-methoxyfluoroquinolone approved by the United States Food and Drug Administration in December 1999. Few side effects of this new antibiotic have been reported, and there are no previous case reports of bradyarrhythmias. We report 2 cases of syncope due to bradycardia in patients who recently began treatment with gatifloxacin.

The carcinogenicity of chrysotile asbestos--a review.

The world production of asbestos has been declining dramatically in recent years, particularly in Europe and the United States. However, increases have occurred in Asian nations and chrysotile is the dominant fiber used. Important uses are in cement products, wallboards, friction products and textiles. From studies in the United States and Great Britain, chrysotile has been shown to increase the risk of lung cancer and to produce mesothelioma in exposed workers.

The hazards of chrysotile asbestos: a critical review.

Chrysotile, or "white", asbestos is the dominant form of asbestos in international commerce today. It accounts for 99% of current world asbestos production of 2 million tonnes. Chrysotile is an extremely hazardous material. Clinical and epidemiologic studies have established incontrovertibly that chrysotile causes cancer of the lung, malignant mesothelioma of the pleura and peritoneum, cancer of the larynx and certain gastrointestinal cancers. Chrysotile also causes asbestosis, a progressive fibrous disease of the lungs. Risk of these diseases increases with cumulative lifetime exposure to chrysotile and rises also with increasing time interval (latency) since first exposure. Comparative analyses have established that chrysotile is 2 to 4 times less potent than crocidolite asbestos in its ability to cause malignant mesothelioma, but of equal potency of causation of lung cancer. The International Agency for Research on Cancer of the World Health Organization has declared chrysotile asbestos a proven human carcinogen. Sales of chrysotile asbestos have virtually ended in Western Europe and North America, because of widespread recognition of its health hazards. However, asbestos sales remain strong in Japan, across Asia and in developing nations worldwide. The claim has been made that chrysotile asbestos can be used "safely" under "certain conditions" in those nations. That claim is not accurate. The Collegium Ramazzini, an international learned society in environmental and occupational medicine, has called for an immediate worldwide ban on all sales and uses of all forms of asbestos, including chrysotile. The rationale for this ban is threefold: (1) that safer substitute materials are readily available, (2) that "controlled" use of asbestos is not possible, and (3) that the health risks of asbestos are not acceptable in either the industrialized or the newly industrializing nations.

Clinical predictors of mortality from asbestosis in the North American Insulator Cohort, 1981 to 1991.

Recorded mortality from asbestosis has increased markedly in the United States in recent decades, from 0.49 to 3.06 per million persons between 1970 and 1990. Although asbestosis is generally considered to be a slowly progressive disorder, little is known about how clinical and exposure parameters among individuals with asbestosis quantitatively predict subsequent risk of death from asbestosis. We followed 2,609 insulators from the North American insulator cohort 10 yr to determine cause of death and to relate clinical findings to risk of death. This group had undergone clinical and radiologic examination between 1981 and 1983 in 19 cities in the United States. Seventy-four (11.0%) of 674 deaths during the subsequent 10 yr were due to asbestosis, according to the best clinical and radiologic evidence available at the time of death. The 10 yr risk of death (expressed as a percentage) due to asbestosis rose sharply with increasing interstitial fibrosis as identified on the baseline chest X-ray, from 0.9% to 2.4%, 10.8%, and 35.4% for International Labor Office (ILO) profusion categories 0, 1, 2, and 3, respectively. Dyspnea, a low FVC, and/or physical examination findings typical of interstitial fibrosis (rales, clubbing, or cyanosis) raised the risk of subsequent death from asbestosis by 2- to 6-fold. The effect of cigarette smoking on risk of death from asbestosis was small and disappeared after adjustment for ILO profusion score.

Inhibition of the transcription factors NF-kappa B and AP-1 underlies loss of cytokine gene expression in rat alveolar macrophages treated with a diffusible product from the spores of Aspergillus fumigatus.

The spores of Aspergillus fumigatus have a survival advantage over other respirable fungal spores in the lung, leading to a number of lung diseases associated with this fungus. We have hypothesized that a component on the spore surface can inhibit the activation of alveolar macrophages, known to play an essential role in immune regulation in the lung. A diffusible product from the spores of A. fumigatus (AfD) inhibited the production of tumor necrosis factor alpha (TNF alpha) protein by alveolar macrophages in an enzyme-linked immunosorbent assay. Using a semiquantitative reverse transcription-polymerase chain reaction, we also demonstrated a potent inhibitory effect of AfD on the production of proinflammatory cytokine transcripts in rat alveolar macrophages. The inhibition occurred at the level of transcription, with AfD inhibiting the synthesis of TNF alpha-and interleukin 6 (IL-6)-specific mRNA transcripts. No effect was seen on the synthesis of interleukin 1 beta (IL-1 beta) cytokine transcripts or on the expression of the housekeeping gene beta-actin. Furthermore, AfD specifically inhibited the activation of nuclear transcription factors NF-kappa B and AP-1, both of which are required for the coordinate upregulation of transcription of the proinflammatory cytokines TNF alpha, IL-1 beta, and IL-6. We conclude that AfD can inhibit normal alveolar macrophage responses by selectively inhibiting the production of key inflammatory cytokines, and that the mechanism of inhibition is primarily at the level of transcriptional activation.

Inhibition of the alveolar macrophage oxidative burst by a diffusible component from the surface of the spores of the fungus Aspergillus fumigatus.

BACKGROUND: Aspergillus fumigatus is a fungus that grows on dead and decaying organic matter in the environment and whose spores are present ubiquitously in the air. The fungus causes a range of diseases in the human lung. A study was undertaken to demonstrate and partially characterise an inhibitor of the macrophage respiratory burst from the surface of A fumigatus spores that could be an important factor in allowing the fungus to colonise the lung. METHODS: The spore-derived inhibitor of the respiratory burst of rat alveolar macrophages, as measured by generation of superoxide anion, was demonstrated in Hank's balanced salt solution extracts of four clinical isolates and an environmental isolate of A fumigatus. The time course of the release of the inhibitor into aqueous solution was assessed and the cytotoxic potential of the spore-derived inhibitor towards macrophages was tested using the propidium iodide method. An oxygen electrode was used to confirm the superoxide anion measurements. Molecular weight cutoff filters were used to determine the size of the inhibitor as assessed in the respiratory burst assay and also by its ability to inhibit macrophage spreading on glass. The crude diffusate from the spore surface was fractionated by reversed phase high pressure liquid chromatography (HPLC) and the fractions analysed for inhibitory activity, protein, and carbohydrate content. RESULTS: A small molecular weight (< 10 kD) heat stable toxin was released from the spores of clinical and environmental isolates of A fumigatus within minutes of deposition in aqueous solution. The key effect of the toxin demonstrated here was its ability to inhibit the oxidative burst of macrophages as measured by superoxide anion release. The inhibition was not due to cell death or detectable loss of membrane integrity as measured by permeability to propidium iodide. The toxin was not a scavenger of superoxide anion. Oxygen electrode studies suggested indirectly that the inhibitor acted to inhibit the assembly of the macrophage NADPH-oxidase complex. Fractions of < 10 kD also inhibited the spreading of alveolar macrophages, confirming that the toxin had an additional effect on macrophages that leads to loss of adherence or impairment of cytoskeletal function. In reversed phase HPLC fractions the inhibitory activity eluted with an associated carbohydrate, although the exact chemical nature of the toxin remains to be elucidated. CONCLUSIONS: This spore toxin may, through its ability to diffuse rapidly into lung lining fluid, diminish the macrophage respiratory burst and play a part in allowing A fumigatus to persist in the lung and manifest its well known pathogenic effects. Future research will be focused on further molecular characterisation of the toxin and elaboration of the effect of the toxin on intracellular signalling pathways involved in the activation of alveolar macrophages.

Detection of unintegrated HIV type 1 DNA in cell culture and clinical peripheral blood mononuclear cell samples: correlation to disease stage.

This article reports on the development of PCR as a sensitive method of detecting both linear and circular forms of HIV-1 unintegrated viral DNA (UVD). The method was developed in a cell line study designed to follow the sequential synthesis of these forms over time. In all T lymphoid lineage cell lines, the full-length linear UVD (LUVD) was synthesized prior to both 1 and 2 LTR forms of circular UVD (CUVD), although all forms were detected by 12 hr postinoculation. Analysis of unstimulated PBMC samples from HIV-positive patients showed a significant difference in the presence of detectable CUVD forms and CDC groups II and IV (p < 0.001) and CDC groups III and IV (p < 0.001). No significance was demonstrated between CDC groups II and III (p > 0.5), linking the presence of CUVD forms to clinical disease and immunodeficiency. We propose that circular unintegrated forms of HIV-1 DNA may play a role in the development of acquired immunodeficiency syndrome.

Recent data on cancer due to asbestos in the U.S.A. and Denmark.

The Authors present data, from the USA and Denmark, dealing with the carcinogenicity of chrysotile. This review considers epidemiological studies on the incidence of bronchogenic carcinoma and mesothelioma in populations exposed to commercial chrysotile and to mixtures of chrysotile and commercial amphiboles, with which the chrysotile is often contaminated. The analyses demonstrate that the risk of lung cancer is similar for chrysotile, amosite and crocidolite on a fiber exposure basis. Chrysotile and amosite appear to produce equal mesothelioma risks. The risk of mesothelioma is four to ten times greater for crocidolite.

Residential proximity to electricity transmission and distribution equipment and risk of childhood leukemia, childhood lymphoma, and childhood nervous system tumors: systematic review, evaluation, and meta-analysis.

In 1979, Wertheimer and Leeper reported an increased risk of cancer mortality among children living near 'electrical wiring configurations' suggestive of high current flow. Since then, numerous, often inconclusively small, investigations with conflicting results have studied the possible association between exposure to electric and magnetic fields (EMF) and health effects. The high prevalence of exposure to EMF has drawn attention to the issue of carcinogenesis. We report here the results of a meta-analysis of 13 epidemiologic studies of residential proximity to electricity transmission and distribution equipment and risk of childhood leukemia, lymphoma, and nervous system tumors. The combined relative risks for leukemia, lymphoma, and nervous system tumors are 1.49 (95 percent confidence interval [CI] = 1.11-2.00); 1.58 (CI = 0.91-2.76); and 1.89 (CI = 1.34-2.67) respectively. The reports of the primary studies were evaluated for epidemiologic quality and adequacy of exposure assessment. We found no statistically significant relation between combined relative risk estimates and 15 indicators of epidemiologic quality. Assessment of EMF exposure in the primary studies was found to be imperfect and imprecise. Additional high quality epidemiologic research, incorporating comprehensive assessments of EMF exposure collected concurrently with surrogate measures of exposure, is needed to confirm these results.

Long term radiological effects of short term exposure to amosite asbestos among factory workers.

Chest radiographs were read from a sub-cohort of 386 factory workers with short term exposure to amosite asbestos (median exposure six months) and long follow up (median 25 years). Prevalence of abnormality was determined independently by two readers from the first film available after 20 years from first employment. Serial films were obtainable for 238 men (median interval from first to last film: nine years). Progression was classified with a direct progression scoring scale. Individual dust exposure estimates were derived from dust counts from two similar plants. With as little as one month or less of employment, about 20% of the films showed parenchymal abnormality and about a third showed pleural abnormality. Those in the lowest cumulative exposure stratum (less than 5 fibre-years/ml) were similarly found to have high rates of abnormality. Dose-response relations were present in the data of both readers. Smokers had higher rates of parenchymal abnormality. On multivariate analysis, cumulative exposure was the exposure variable most closely related to parenchymal abnormality, and time from first employment was the variable most closely related to pleural abnormality. Progression (including first attacks) 20 or more years after ceasing employment occurred and was more common for pleural than for parenchymal abnormality. It is concluded that with exposure to high concentrations to amosite such as existed in this factory and with follow up for at least 20 years, (1) exposure for as little as a month was sufficient to produce radiological signs of parenchymal and pleural fibrosis, (2) no cumulative exposure threshold for parenchymal and pleural fibrosis was detectable, and (3) parenchymal and pleural progression were still detectable >/= 20 years after the end of exposure.

Comparison of hepatitis B virus subtyping of d/y determinants by radioimmunoprecipitation assay and the polymerase chain reaction.

Using a double polymerase chain reaction a method was devised for detecting and subtyping hepatitis B virus DNA in serum samples. Primers from the S-gene were selected from the sequence analyses of five HBV HBsAg subtypes, to amplify HBV DNA and subtype for y specific DNA. Thirty-eight samples were subtyped for d and y determinants by radioimmunoprecipitation assay (RIPA) and the polymerase chain reaction (PCR). Subtyping by PCR and RIPA was in agreement in 100% of subtype y samples and 83.3% of subtype d, giving an overall correlation of 92.1%. As a third comparison, 12 amplified samples were digested by the restriction enzyme Sau 3A, which differentiates between subtypes y and d. The digest results agreed with PCR in 83.3% of the samples. In addition, we compared our standard phenol/chloroform extraction against a rapid one step method. The phenol/chloroform stage was found to be essential for the removal of nucleases and polymerase inhibitors present in sera.