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Biomedical subjects

D M Evje

Publications and source records attributed to D M Evje.

6 recordsLinked to original sources
PubMed1985

Man's mercury loading from a dental amalgam.

The release of mercury from an amalgam surface in natural saliva during cyclic loading, as well as under static conditions, simulating the clinical conditions of chewing and rest, has been studied using a nuclear tracer technique. Cyclic loading strongly promoted degradation of the amalgam surface in the saliva environment. Corrosion products were found to be loosely bound on the amalgam surface and could be removed by brushing similar to toothbrushing. Most of the mercury released from the surface was present in amalgam particles, produced during the cyclic loading procedure. The daily release of ionic mercury was estimated to be approximately 3 micrograms/cm2, according to the model experiment. Extrapolating the present findings to clinical conditions, man's ionic mercury intake from dental restorations may be at the same level as the total mercury intake from food and drink.

Dental Amalgam↗
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↗
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↗