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Biomedical subjects

D Welker

Publications and source records attributed to D Welker.

At least 73 records · Page 4Linked to original sources
PubMed1979

[Biological responses to filling materials with special reference to the composite material evicrol--an experimental study (author's transl)].

The biological responses to the composite filling material Evicrol were tested by temporarily differentiated implants in rats. Type and degree of the inflammatory reaction as well as the intensity of connective tissue fiber formation were used as criteria for evaluation of the histocompatibility of the subcutaneous implants. As compared to other composite filling materials, Evicrol was found to produce a relatively severe irritation of the tissue. In comparison with silicate cements and also with silicopolyacrylate cement, composite materials including Evicrol were responded to by for less pronounced chronically toxic effects.

Composite Resins↗
PubMed1979

[Addition cross-linked silicone impression materials].

The principle of the polyreactions "polymerization", "polycondensation" and "polyaddition" is explained and described in detail for silicone impression materials. In the light of laboratory findings (quasi-viscosity, plasto-elasticity, dimensional and weight behaviour), three alginate materials, one condensation cross-linked silicone material, two addition cross-linked silicone materials and one polyether material are compared and evaluated with regard to their clinic-relevant properties.

Alginates↗
PubMed1978

[Report on the capsule dosage and mixing system. 1. Development, current state and prospects].

The author gives a survey of the development, present state and developmental possibilities of the capsule system (mechanical processing of dental materials predosed in capsules). Experimental studies and accounts of clinical experience of the last ten years show that the capsule system is a scientifically founded procedure characterized by a considerable effect of rationalization, the quality of work being improved. The advantages of the procedure are demonstrated by personal studies and the literature. The advantages lie in the fields of ergonomics, materials science and economics. They are in evidence especially in processing filling materials.

Capsules↗
PubMed1978

[Report on the capsule dosage and mixing system. 2. Development, design and mode of action of a mixing machine for dental materials measured out in capsules].

The author presents a mixing apparatus for dental materials predosed in capsules. It is characterized by a novel principle of motion and great efficiency, which permits to triturate, in a short time and the best possible manner, all luting and filling materials suited for mechanical mixing, including amalgam alloys. Redrawings of quick-motion pictures illustrate the mixing process in the capsule.

Capsules↗
PubMed1978

[Report on the capsule dosage and mixing system. 3. Suitability testing from a technological and clinical point of view].

The results from experiments with composite filling materials, silicate cements, stone cements, polyacrylate cements, EBA cements and amalgam testify to the suitability of a mixing apparatus already presented (cf. Par II). Apart from industrial predosed products, well known multicomponent materials prepared until now manually, among which Evicrol, were mixed mechanically.

Acrylates↗
PubMed1978

[Report on the capsule-dosage and mixing system. 4. Correctness and precision in the dosage of multi-component materials; pre-dosage in daily practice as a preliminary solution to the capsule-dosage and mixing system].

The significance of the factors "accuracy" and "precision" in the preparation of multicomponent materials is outlined with special regard to problems related to dosage. The present technological development permits to shift the responsibility for accuracy and precision to the manufacturers of dental materials. In view of the applicability of the capsule dosing and mixing system, the author presents an intermediate solution (based on the experimental verification of various dosing methods) that permits to benefit from the main advantages of the capsule system in everyday practice prior to the establishment of centralized dosing facilities.

Capsules↗
PubMed1976

[Results of experimental studies on new materials for dental models].

Newly developed cast materials (special stone plaster and plastic materials for single-stump casts) were tested for their setting behaviour and strength, their ability to reproduce fine-profiled surfaces and, in combination with standarized silicone impressions, for their dimensional behavior. With reference to the authors' experience, the suitability of these materials for making casts is critically evaluated.

Biophysical Phenomena↗
PubMed1976

[Experimental studies on the effects of various dosages and working temperatures on the flow behavior and the elastic characteristics of a normally flowing silicone casting investment].

The main purpose of the present paper was to study the elastic properties of silicone impression material containing an overdose or underdose of hardener as a function of the time elapsed from the start of the mix. Additional measurements of the quasi-viscosity as a function of dosage and mixing temperature were performed to cover the plasto-elastic transitional phase after mixing. The experimental conditions have been established according to the results from previous processing tests. Overdosage as well as underdosage of the hardener caused (according to its extent) marked or in part considerable deterioration of the elastic properties. The differences from normodosed material decreased with the time elapsed from the start of the mix. Having discussed his observations from the viewpoint of materials science, the author draws conclusions as to the processing of silicone impression material and to the differential indication of alginate and silicon materials for one-stage impression.

Dental Impression Materials↗
PubMed1976

[Comparative studies on the cytotoxic effect of composite filling materials and silicate cement].

The biologic compatibility of two composite materials (Cosmic, Epstic) based on Bowen's resin and two silicate cements (Frontasil, Silicap) and theirs components were assessed in cell culture. The compounds eluated from the material specimens under physiological conditions affected monolayer cultures of rat fibroblasts and rat epithelial cells (linr RL-19). Silicate cement eluate brings about death of cells due to high concentration of H-ions. Neutralized eluate of freshly prepared Cosmic, Estic and Frontasil caused the same cell damage which was less pronounced following Silicap eluate. The toxicity was markedly reduced following use of an eluate material which had a setting time of 24 hours. After the 2nd and 3rd elution of same specimen the cytoxicity was noticeably weakened, however, it was still demonstrable. The patterns of injury were different following composite material and silicate cement. All tested components soluted in Eagle medium have an irritating effect on the cultivated cells.

Animals↗
PubMed1975

[Clinical aspects and etiology of prosthesis-induced changes in the oral mucosa].

The clinical picture and the aetiology of prosthesis-induced alterations of the oral mucosa are presented. In the light of personal gerontological observations, the authors deal with the mechanical irritation produced by the prosthesis as the main aetiological factor and discuss its effects on prophylaxis, diagnosis and therapy.

Aged↗
PubMed1975

[Tissue compatiblity of stomatologic materials in cell cultures].

The paper contains results of investigations on the suitability of cell cultures for biological testing of soluble substances from dental cements and their components. The preparation of the specimens as well as the elution process are described. Furthermore the culture system of cell populations in vitro and representative biological parameters are reported.

Adult↗
PubMed1975

[Comparative in vitro study on cellular reactions to soluble components of EBA and phosphate cement].

While the eluate of EBA cement does not have any toxic effect on the cell populations, the cells are noticeably damaged by the pH-corrected eluate of freshly mixed phosphate cement. Comparison between the cellular reaction to eluates and the solubility of the cements shows that the toxic effect is not a priori dependent on the composition of the material, but on the degree of dissolution which is primarily determined by the environment and the mixture ratio. The solutions of cement powder do not have any irritating effect on the cultivated cells. However, due to its content of eugenol, the EBA cement fluid solved in a considerably weaker concentration in the culture medium than the phosphate cement fluid damages the cells to such an extent that they die.

Animals↗