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Biomedical subjects

K Dermann

Publications and source records attributed to K Dermann.

17 recordsLinked to original sources
PubMed1991

[In vitro study on the corrosion behavior of two amalgams in direct contact to different cast metal alloys].

The direct contact between amalgam and cast metal may enhance electrochemical reactions. In a study to determine the amount of mercury released in these reactions, six cast metal alloys with increasing precious metal contents were placed in immediate contact (contact area 10 mm2) to two non-gamma 2-amalgams (Amalcap, Valiant) and incubated with artificial saliva at 37 degrees C for up to 8 weeks; then the salivary mercury concentrations were measured. After the end of the incubation period the case metal surfaces were analyzed by ESCA for metal appositions. The results showed that direct contact between amalgam and cast metal after storage in artificial saliva for 8 weeks resulted in a minor release of mercury (22.7 +/- 10.63 ng/ml Hg). On the cast metal plates themselves only smallest mercury concentrations could be demonstrated. These in vitro tests have shown again that, although charge transfers do occur when different metals are in direct contact, they do so only to a minor degree, because of the passivation processes involved.

Corrosion↗
PubMed1979

[Developmental trends in dental amalgams].

The new copper-rich silver amalgams differ from the standard amalgams because the corrosive-prone gamma 2-phase is absent. They are also superior to standard amalgams in terms of creep values. Edge strength therefore is improved.

Copper↗
PubMed1979

[Heat expansion of composite resins stored in water].

Thermal expansion coefficients between 10 C and 60 C were determined in 10 degree increments with 10 plastic filling materials and two plastics used for protheses (3 specimens each). The coefficients became larger as the temperature increased. The composites with 20 to 60.10(-6)/C are closest to the thermal expansion coefficient of the tooth; unfilled plastics with 80 to 130.10(-6)/C, the farthest removed. Plastics containing less anorganic filling material demonstrated thermal expansion coefficients between 70 and 90.10(-6)/C. Water absorption did not appear to influence the expansion.

Composite Resins↗
PubMed1978

[The SI unit system].

The German "Law for Units of Measure" have restricted the number of units of measure acceptable for business and official dealings. As of January 1, 1978, many common units are no longer to be used. They have been replaced by less familiar units.

Germany, West↗
PubMed1977

[Bending strength in modeling materials].

The bending strength and modulus of elasticity of 15 materials were measured. 9 of them were hard plasters. Five were plastics with filling material, one a hard plaster with copper. On the basis of modelling calculation a bending strength of 20 N/mm2 is necessary. It is exceeded by 12 of the materials and not quite attained by 3 of them.

Dental Impression Materials↗
PubMed1976

[Compression of amalgam specimens under various loads].

To test the behavior of amalgam fillings under masticatory load, 72 cylindrical amalgam specimens (d=5mm, h=10mm) were exposed to alternating loads changing from zero pressure to a pressure of 10 N/mm2. The tests were made in a conventional and four silver amalgams rich in copper, in water baths of 30 degrees, 37 degrees, 50 degrees, and 60 degrees C. Compression of the specimens results, which increases proportionally to the cube root of the number of alternating loads and with rising temperature. The compression lies between 0.3 per cent to 5 per cent of the original length after 10,000 alternating loads, depending on amalgam and temperature. Compressive strength increased under alternating load.

Dental Amalgam↗