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Biomedical subjects

D Brune

Publications and source records attributed to D Brune.

At least 55 records · Page 3Linked to original sources
PubMed1985

A model for recording mercury release from an amalgam surface.

The release rate of mercury from a conventional, a dispersed phase or a spherical high copper content amalgam under static conditions in stimulated or artificial saliva has been measured and found to decrease approximately exponentially with time. A higher initial release rate was observed for mercury in stimulated saliva than in artificial saliva during the in vitro experiments. In a pilot study corrosion current was recorded from an amalgam specimen immersed in saliva, and was found to decrease approximately exponentially with time. After brushing the surface of the amalgam during two subsequent periods, in a manner similar to toothbrushing, an increase in corrosion current was measured indicating the removal of loosely bound corrosion products. A model describing the periodical mercury release from an amalgam surface has been proposed.

Corrosion↗
PubMed1985

Protective effect of selenium on lung cancer in smelter workers.

A possible protective effect of selenium against lung cancer has been indicated in recent studies. Workers in copper smelters are exposed to a combination of airborne selenium and carcinogens. In this study lung tissue concentrations of selenium, antimony, arsenic, cadmium, chromium, cobalt, lanthanum, and lead from 76 dead copper smelter workers were compared with those of 15 controls from a rural area and 10 controls from an urban area. The mean exposure time for the dead workers was 31.2 years, and the mean retirement time after the end of exposure 7.2 years. Lung cancer appeared in the workers with the lowest selenium lung tissue levels (selenium median value 71 micrograms/kg wet weight), as compared with both the controls (rural group, median value 110; urban group, median value 136) and other causes of death among the workers (median value 158). The quotient between the metals and selenium was used for comparison: a high quotient indicating a low protective effect of selenium and vice versa. The median values of the quotients between antimony, arsenic, cadmium, lanthanum, lead, chromium, and cobalt versus selenium were all numerically higher among the cases of lung cancer, the first five significantly higher (p less than 0.05) in 28 of the 35 comparisons between the lung cancer group and all other groups of smelter workers and controls. The different lung metal concentrations for each person were weighted according to their carcinogenic potency (Crx4 + Asx3 + Cdx2 + Sbx1 + Cox1 + Lax1 + Pbx1) against their corresponding selenium concentrations. From these calculations the protective effect of selenium was even more pronounced.

Aged↗
PubMed1984

Chromium, cobalt and lanthanum in lung, liver and kidney tissue from deceased smelter workers.

Lung, liver and kidney tissue concentrations of chromium, cobalt and lanthanum from 66 deceased copper smelter workers have been compared with 14 controls. Samples were taken in connection with ordinary autopsies at the local hospital. Neutron activation analysis was used. The mean exposure time for the smelter workers was 30 y, the mean time to date of death after termination of exposure was 7.4 y. A four-fold increase of chromium (p = 0.001) and a two-fold increase of cobalt (p less than 0.001) and lanthanum (p = 0.013) in lung tissue was found for smelter workers compared to controls. Of the smelters nearly one third died from malignancies (approximately 10% from respiratory cancer) and approximately 45% from cardiovascular disease. In the control group nearly 80% died from cardiovascular diseases and no malignancies were found. In lung tissues the concentration of chromium, cobalt and lanthanum did not decline with time after exposure had ended, indicating a long biological half-time. The causes of death could not be related to a single factor. The findings indicate a multifactorial genesis.

Aged↗
PubMed1984

Initial acidity of dental cements.

The acidity in aqueous solutions following release of acid components from glass ionomer, silicate, zinc phosphate and zinc polycarboxylate cements has been registered by pH measurements. One brand of each type was studied. Initial setting was accomplished at two different temperatures; 23 degrees C and in the interval from 23 degrees C to about 60 degrees C. In the latter case external heat was transferred to the samples by infrared radiation for a period of 2 min. The highest acidity was associated with the silicate specimen, while the lowest acidity was recorded for the zinc polycarboxylate specimen. Exposure to infrared radiation resulted in a reduced acidity for all types of cements. The effect of infrared exposure was most pronounced for the silicate specimens, resulting in a reduction of acid release by a factor of about 10 compared to the nontreated samples. The resistance to acid release was found to be improved by a factor of about 5 for the glass ionomer and about 3 for the zinc phosphate cement treated in a similar way. Clinically, it seems possible considerably to reduce the risk of pulpal injuries associated with the insertion of silicate restorations by using a moderate infrared radiation treatment. Furthermore, the susceptibility of glass ionomer cements to a high initial erosion should be reduced by the use of such a technique. After exposure of the glass ionomer and silicate specimens to infrared radiation at the temperature interval applied, the samples had a more glossy, tooth-like appearance compared to the nonexposed samples, improving the aesthetic properties.

Acids↗
PubMed1984

Initial corrosion of amalgams in vitro.

The amounts of copper, mercury, silver or zinc released from two brands of freshly prepared, lathe cut amalgams and from one brand of dispersed phase type amalgam into artificial saliva have been measured. Samples were immersed in the solution a few minutes after the end of trituration and exposed statically for periods of up to about 4 days. The initial mercury release from such specimens could exceed the long term mercury release from old amalgams by more than two orders of magnitude. The measurements indicate that during the first day after insertion of two amalgam fillings, each with an assumed surface area of 1 cm2 and under presumably static conditions, mercury at the level of more than twice the mercury food and drink intake could be released in the oral cavity. This is, however, a situation which appears infrequently, e.g. following dental treatment once a year. The amounts of copper and zinc released initially were considerably lower than the corresponding food and drink intake values, while silver might be on the same level. The measurements were conducted using nuclear tracer techniques.

Copper↗
PubMed1984

Corrosion resistance of a passivated and non-passivated cobalt-chromium alloy.

The release of cobalt and chromium from a passivated and non-passivated cobalt-chromium alloy in artificial saliva has been measured using nuclear tracer technique. The corrosion resistance of the passivated specimens was improved by a factor of about four compared to the non-passivated specimens with regard to the initial cobalt release. The specimens were exposed to the saline solutions for periods up to about 8 wk. The cobalt release is associated mainly with electrochemical corrosion processes, since particulate matter retained on a filter was only registered to a minor extent. It is suggested that the decrease in release of cobalt and chromium after passivation is connected to the formation of Cr-O and/or Cr-OH bonds in the protective film which impede the movement of cobalt and chromium from the alloy into the saliva.

Chemical Phenomena↗
PubMed1984

Lung retention of antimony and arsenic in hamsters after the intratracheal instillation of industrial dust.

Airborne factory dust (with a volume median diameter of 5.0 micron and a geometric standard deviation of 2.1 micron) from a Swedish copper smeltery contained antimony (Sb) (1.6 weight %) and arsenic (As) (19 weight %). The dust was neutron activated and intratracheally instilled in hamsters. In vivo measurements of lung clearance were undertaken of the radionuclides 76As, 122Sb, and 124Sb. Comparison was made with pure substances of antimony trioxide (Sb2O3) and arsenic trioxide (As2O3). Two phases were recognized in the clearance curves. The approximate half-time for the initial phase was 13 h for As2O3, 20 h for arsenic dust, about 40 h for Sb2O3, and about 30 h for antimony dust. The second phase had an approximate half-time of 20-40 d for Sb2O3 and antimony dust. Because of the short physical half-life of 76As, the second phase of the lung clearance was not possible to follow for AS2O3 and arsenic dust. The observed differences in clearance were primarily related to the solubility of the dust particles in saline, while particle size seemed to be less important in this instillation experiment. The low solubility of antimony in factory dust combined with a long biological half-time may be of importance in explaining the observed lung accumulation of antimony in exposed workers. The greater solubility and shorter biological half-time restricted the lung retention of arsenic.

Animals↗
PubMed1983

Gastrointestinal and in vitro release of copper, cadmium, indium, mercury and zinc from conventional and copper-rich amalgams.

Particles of a conventional lathe-cut, a spherical non-gamma 2 and a copper amalgam have been gastrointestinally administered to rats for the purpose of evaluation of the dissolution resistance. The animals were sacrificed after 20 hrs. The contents of copper, cadmium, indium, mercury and zinc in kidney, liver, lung or blood were measured using nuclear tracer techniques. From a copper amalgam an extreme release of copper was demonstrated. This study stimulates the clinical condition of elemental release from swallowed amalgam particles after amalgam insertion or after removal of old amalgam fillings. Specimens of the same types of amalgams were also exposed to artificial saliva for a period of 10 days. The amounts of copper and mercury released were measured with flame and flameless atomic absorption spectrophotometry respectively. The levels of copper and mercury released from the copper amalgam were approximately 50 times those of the two other amalgam types studied.

Animals↗
PubMed1983

Surface degradation of amalgams in vitro during static and cyclic loading.

Corrosion during static creep of two gamma 2-containing and one dispersed phase amalgam immersed in artificial saliva has been observed, using SEM, to occur in gamma 1-grain boundary regions where grain boundary sliding and dislocation slip take place. Cracking in the interior of gamma 1-grains has also been found, in particular for dispersed non-gamma 2 amalgam. The combined action of corrosion and stress favored the formation of cracks. Signs of similar creep processes which may promote cracks have also been noted after cyclic loading where the accumulative strains were much lower than in the static creep experiments. Due to these low strains and short immersion times corrosion attacks of the same kind as under static loading can only be assumed. Using nuclear tracer technique quantitative measurements of the corroded material from samples exposed to cyclic loading showed the dispersed non-gamma 2 amalgam to release more Hg, Cu and Zn than the two gamma 2-containing amalgams and that 50-90% copper and mercury were present as particulate matter. These observations can be explained on the basis of different tendencies to cracking in the amalgams. Cyclic loading increases the rate of degradation by one or two orders of magnitude compared with corrosion without loading. Reported studies of marginal degradation in non-gamma 2 amalgams compared with gamma 2-containing amalgams do not agree with the present in vitro experiments.

Corrosion↗
PubMed1983

Corrosion of dental alloys studied by implantation and nuclear tracer technique.

A method for the study of in vivo corrosion of various dental materials such as amalgams, gold, and chromium-cobalt alloys combining implantation and nuclear tracer techniques is described. Radioactive and nonradioactive implants were inserted subcutaneously in the backs of two groups of rats. After 5 days all animals were killed. The adjacent tissue was submitted to histopathological examination. The animals exposed to radioactive amalgams and chromium-cobalt disks with activity levels of 2-4 mCi showed local tissue reactions identical to those seen in sham-operated animals--that is, inflammation and formation of granulation tissue. In contrast, the rats exposed to radioactive gold foils with activity levels of about 20 mCi suffered heavier damage at the implantation site, with loss of hair and some necrosis, in addition to the inflammation and granulation tissue formation. There was no kidney damage. The release of mercury, gold, or cobalt into the adjacent tissue and the kidney was measured by means of gamma-ray spectrometry.

Animals↗
PubMed1982

Heat treatment of glass ionomer, silicate, zinc phosphate and zinc polycarboxylate cements.

The compressive strength and erosion resistance of glass ionomer, silicate, zinc phosphate or zinc polycarboxylate cements, submitted to heat treatments at 50 degrees or 70 degrees C after mixing, have been assessed. Zinc phosphate cement specimens showed a marked reduction in compressive strength properties and erosion resistance, while minor improvements in compressive strength were observed for various brands of the other types of cements. For silicate cement a considerable improvement in erosion resistance was noted. One brand showed a reduction in the release of phosphate amounting to approximately a factor of 20. The various improvements observed may be clinically exploited by exposing the restoration after insertion to radiation from an external heat source which deposits radiation energy in the surface or bulk of the restoration.

Chemical Phenomena↗
PubMed1982

Improvement of erosion resistance of a silicate cement by infrared radiation.

Silicate cement specimens have been exposed to infrared radiation for the purpose of improving the erosion resistance. Exposure for periods of 3-10 min, corresponding to a surface temperature of about 60-70 degrees C, resulted in a reduced phosphate release of about 3-5 times that of a non-exposed group. The temperature distributions on the surface, as well as in a position 5 mm beneath the surface, were measured with thermocouples during irradiation. A difference in temperature of about 20 degrees C was registered between the surface and interior positions. The technique may be clinically exploited by exposing the restoration after insertion to a small infrared radiation source, available on the commercial market.

Chemical Phenomena↗
PubMed1982

Corrosion of gold alloys and titanium in artificial saliva.

Two types of gold alloys and one type of pure titanium have been submitted to corrosion in artificial saliva for periods of up to about 2 months. The release of copper, gold or silver from the gold alloys as well as titanium from the titanium matrix was measured with nuclear tracer technique. The physical/chemical state of the corrosion products of gold alloys referring to the ionic state or presence in particulate form has been examined retaining the particulate matter on a glass filter. Copper was observed to be mainly present in the ionic state. Considerable amounts of gold were observed to be retained on the glass filter explained by the presence of gold in particular form or as a component of a dispersed colloidal phase. The estimation of the release of titanium was registered by the tracer nuclide 46Sc assuming particulate matter to be deteriorated from the titanium surface.

Chemical Phenomena↗
PubMed1982

Microstructure and strength properties of silicate and glass ionomer cements.

Microstructure characterization of silicate and glass ionomer cements has been carried out using, SEM, EDAX and ion microprobe techniques. The distribution of aluminum, calcium, fluorine, phosphorus or silicon was measured in the set cement surfaces. Cracks in the cement specimens produced by mechanical breaking, in contraction during setting, or as a result of SEM preparation were observed to occur mainly in the matrix and in the interface between matrix and particle. Powders of silicate and glass ionomer cements were separated into various fractions using sieves or cyclone separation technique. Compressive strength measurements of specimens made of powders with various size distributions have been assessed. The fractionation did not reveal any strong effect on the compressive strength properties either for the silicate or the glass ionomer cement.

Chemical Phenomena↗
PubMed1982

Antimony in lung, liver and kidney tissue from deceased smelter workers.

Tissue concentrations of antimony in lung, liver, and kidney tissue from a group of deceased smelter workers from northern Sweden have been compared with those of a group of persons without occupational exposure from a nearby area. Neutron activation analysis was used to determine the antimony concentration of lung tissue from exposed workers; these concentrations were 12-fold higher than those of referents (p less than 0.001). For lung tissue there was no tendency towards decreased antimony concentrations with time (up to 20 a) after the cessation of exposure, and this result indicates a long biological half-time. The highest values were found for workers who had worked for many years at the roasters and in the arsenic and selenium departments. There was no significant difference between the antimony concentration of the lung tissue from workers who had died of lung cancer and those of persons who died of other malignancies, cardiovascular disease, or other causes. This finding does not however rule out the possibility of a role for antimony in the etiology of lung cancer among smelter workers since multiple factors may have been operating. The antimony concentration of the liver tissue and the kidney cortex did not differ from the corresponding values of the reference group; this finding indicates either a short biological half-time or insignificance for the systemic distribution of antimony.

Adult↗