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O Christen

Publications and source records attributed to O Christen.

6 recordsLinked to original sources

[Problem-based learning (POL) in environmental medicine].

"Environmental medicine" is a new sub-discipline in the spectrum of medical specialization in Germany. The Berlin Academy of Occupational Medicine and Health Protection, now a branch of the Berlin Chamber of Physicians, developed a 200-lesson curriculum for physicians who want to specialize in this field. Coincidentally during the initial courses, the attendants were already highly qualified ("Facharzt"-level) and experts in various occupational fields, and hence the composition of the classes was highly heterogeneous on the levels of practical experience as well as theoretical knowledge. The Academy therefore decided to change the teaching method to Problem-Oriented Learning (POL). This required training tutors for small learning groups, supervision for these tutors and supplying adequate teaching materials and a stimulating environment for the student. The "Arbeitsgruppe Reformstudiengang Medizin" (Medicine Curriculum Reform Project) at the Berlin Humboldt University as well as the Dutch Rijksuniversiteit Limburg in Maastricht helped in the process of conceptualization. Participants worked in groups of up to 8 persons under non-directive tutors. A new "case" was presented every day, and the students developed individual learning goals according to the Seven Steps-method, which were then researched individually and with the help of outside experts. The findings were reported back and discussed in the group. Initially there was irritation, but after two or three days participants got used to not being lectured. Instead of being passive recipients of expert knowledge they felt that the POL method of learning enhanced their competence to act independently.

Curriculum↗

[6 dentin adhesive products subjected to controls in vitro].

The aim of this in vitro study was to assess of the biocompatibility of 6 adhesive dental products (Cavalite, Dual Cement, Fuji Type II, Gluma, Ketac Bond, Scotch Bond) using cell cultures of human pulps and a standardized method. It was thus possible to improve the scale of biological activity proposed by Regad et al., (1989). The specific behaviour of the cells in the contact and adjacent zones has been added to the assessment of the cellular reactions of the whole culture. These criteria allowed the clear differentiation of the toxicity and the biocompatibility of the products. The following estimations were made: Gluma and Fuji Type II "toxic", Cavalite "acceptable", Scotch Bond "not significant", Ketac bond and Dual Cement "acceptable" and "not significant" with a "toxic" tendency.

Acrylic Resins↗

[Substitute model of an in-vitro biological trials. I. Standardized method using human pulp cells].

To ascertain the biocompatibility of dental materials, an in vitro biological test using cultures of human pulp cells was designed as an alternative to the in vivo method using human teeth. The cells were cultured from fresh explants of pulp germs and the 4th generation of cells (P4) was shown to be very similar to the controls. The comparison between the results of the in vitro cell cultures (obtained by rating the cells' growth and the histomorphology) and those of the controls (histologic rating of the pulpal response) indicated that the developed cell culture method was suitable for the preliminary evaluation of pulpal protective materials.

Biocompatible Materials↗

[Substitute model for in-vitro biological testing. II. Quantitative evaluation of the biocompatibility of dental products].

A biological model for evaluating pulpo-dentinal capping materials is described. The model uses cultures of human pulp cells which are explanted to form cell monolayers. Four products already tested in vivo on teeth subsequently extracted for orthodontic reasons were laid directly over these cultures and observed after 7, 14, 21 and 28 days, corresponded to the in vivo test periods. The growth and morphology of the cells were similar for both test systems, indicating comparability between the two biological models as well as the validity of the developed in vitro method. A preliminary scale of biological activity is proposed which could be useful for preliminary screening of materials.

Biocompatible Materials↗