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Biomedical subjects

W Finger

Publications and source records attributed to W Finger.

At least 73 records · Page 4Linked to original sources
PubMed1980

Effect of thickness of peridental restorations on the casting precision.

The present study has shown that the precision of peridental gold alloy castings depends both on the specific properties of the investment used and on the thickness of the pattern. In all cases the inside diameter of the castings decreased with increasing thickness. The most accurate results were obtained with an experimental investment characterized by a setting expansion of 0.05%, a thermal expansion high enough to compensate for the alloy contraction during cooling from solidus to room temperature, and a compressive strength of only 27 kg/cm2 at 670 degrees C.

Dental Casting Investment↗
PubMed1979

Die-spacing technique by diffusion precipitation.

The present study has shown that it is possible by utilizing the principle of diffusion to precipitate on stone dies an adequate resin spacer of uniform and desirable thickness. Details and variables of the technique are described. The precipitation technique is simple and requires a minimum of time and equipment. This spacer technique opens up gateways for a new and improved casting technique cleared of most of the variables affecting the precision of the methods employed up till now. A new gypsum bonded investment for the new casting technique is being developed.

Acetone↗
PubMed1977

[Porosity of composite filling materials].

The porosity of composite materials was investigated. For the 5 materials tested the values varied between 5.9 and 2.2 vol. %. The volume of porosity could be reduced markedly by a short application of pressure upon the mixed material. Pressure and time of pressure were checked separately, and it could be shown that the percentage of porosity reduction was correlated almost completely with the viscosity of the composite.

Composite Resins↗
PubMed1976

[Inhibition of polymerization by oxygen in composite filling materials and enamel sealers].

The oxygen inhibition upon the polymerization of composite materials was investigated. The method permitted the avoidance of oxygen inhibition even in cases where the special matrix could not be used. The results can be summarized as follows: 1. The depth of inhibition, when atmospheric air is admitted, varies, according to different brands of composites, between 25 and 105 mum. 2. By conducting a protective gas over the surface of the polymerizing material, the contact of oxygen is avoided just as if a matrix were used. 3. Avoidance of oxygen is particularly important during the setting period of the material, i.e. the time between the end of mixing and the end of setting. 4. Polymerization under a protective gas makes it possible to polymerize even very thin layers of material and therefore widens the scope of use for sealants in caries prophylaxis.

Dental Materials↗
PubMed1975

[Mechanical-dynamic properties of prosthesis plastics].

Comparative studies on the mechanic and molecular properties of heat- and self-curing polymers (PMMA) showed the following results: 1. The glass-transition temperature of heat- and self-curing polymers clearly shows measurable differences also as a function of their storage conditions. However, this is hardly of any clinical or practical significance. 2. The modulus of elasticity values of heat and self-curing polymers are not significantly different in the range of the usually applied temperatures. However, water-uptake considerably reduces the rigidity. 3. Overloading or fatigue failures do not show any clear differences in morphological characteristics. The practical influence of smaller long-term inflation strength of self-curing polymers has not yet been sufficiently proven. 4. Heat and self-curing polymers are identical as basic materials for dentures from the point of view of material technology.

Cold Temperature↗
PubMed1975

[The cast structure after vacuum-pressure casting and centrifugal casting].

Evaluation of polished sections revealed the following: 1. Grain size in marginal areas of the crown is, in general, smaller than it is in the occlusal region. 2. Grain size varies depending on the casting method applied. Differences in hardness were found only to a limited extent. They were not always in line with the grain structure. This phenomenon deviating from the rule cannot satisfactorily be explained. The piping distribution was in accordance with observations made so far.

Crowns↗