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Biomedical subjects

K Dermann

Publications and source records attributed to K Dermann.

At least 19 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↗
PubMed1983

Detecting margin leakage of dental composite restorations.

The degree of microleakage between a restoration and the cavity wall is difficult to quantify objectively. A silver-staining method is used and compared to the radioisotope method with results that indicate a superior definition and more accurate evaluation of microleakage. In addition to the accuracy, two advantages are presented: (1) scoring of the leakage can be refined and divided into more precise numbers, and (2) teeth can be observed directly in a microscope without resorting to the indirect interpretation of film or photograph.

Calcium Radioisotopes↗
PubMed1981

Marginal adaptation of BIS-GMA-based composites containing various diluents.

The aim of this study was to determine how otherwise acceptable diluent monomers affect the marginal adaptation of BIS-GMA-based composites. Based on the results of the investigation, the following conclusions can be drawn: 1. Addition to dimethacrylate diluents containing (CH2) recurring units generally yields composites having better marginal adaptation than do those containing (CH2 CH2 O) groups. Best marginal adaptation for a single diluent is obtained for compositions using 1, 4 and 1, 10-polymethylene glycol dimethacrylate as diluent. 2. Marginal adaptation is improved on lowering the diluent concentration. Optimum adaptation will be obtained for a formulation containing a minimum percentage of diluent with clinically acceptable working properties. 3. Volume changes on temperature cycling resulting from differences in thermal expansion coefficients of composites do not effect the marginal integrity as much as does curing shrinkage.

Acrylates↗
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↗