S.K. Thoden van Velzen

Cervical external root resorption

Abstract Cervical external root resorption is frequently confused with internal resorption, yet a correct diagnosis is of great importance because the methods of treating these two conditions differ fundamentally. Views on the aetiology of cervical external root resorption are disparate, but it seems most plausible that the cause is chronic inflammation of periodontal tissues.Abstract Cervical external root resorption is frequently confused with internal resorption, yet a correct diagnosis is of great importance because the methods of treating these two conditions differ fundamentally. Views on the aetiology of cervical external root resorption are disparate, but it seems most plausible that the cause is chronic inflammation of periodontal tissues.

Polyethylene tubes as a model for the root canal

Polyethylene tubes, closed at both ends with casting wax and with four perforations in the middle, were implanted subcutaneously in rats and evaluated as a research model simulating the root canal. As controls, wax bars and unperforated tubes were implanted. Attention was given to the reaction of the tissue surrounding the perforated empty tube, the tissue reaction to polyethylene and casting wax, and to the displacement of the tubes.

Electronic determination of root canal length

Root canal length was measured in an experimental model composed of the severed halves of porcine mandibles, using an electronic device for locating the apical foramen. The measurements, each taken independently by two or three observers, were compared with radiographic working length determinations, and with direct visual measurements made after the teeth were extracted. Under the conditions of the experiment, electronic determination of endodontic working length did not compare favorably with radiographic determination of working length.

Reactions of the living organism to dead and fixed dead tissue.

Two series of experiments were conducted on the reactions of the living organism when in contact with dead and fixed dead tissue. The inflammatory reaction to necrotic tissue was less severe than the reaction to fixed necrotic tissue. The results led to the tentative conclusion that chronic periapical inflammation most likely is caused by living microorganisms.

Long-term results of the implantation of glutaraldehyde-fixed tissue

Abstract Glutaraldehyde-fixed autologous young connective tissue was implanted in rabbits for periods of 4, 6, 8, and 12 months, respectively, to evaluate the long-term effects of glutaraldehyde fixation. It was concluded that the implants elicit very little reaction in the surrounding tissues and that the fixed tissue is slowly invaded by vital cells and probably evokes an immune response. It is likely that, although glutaraldehyde-fixed dead tissue provokes less reaction than both unfixed and formaldehyde-fixed dead tissue, in the long term it is also broken down and phagocytized.

Tissue reaction to implantation of unfixed and glutaraldehyde-fixed heterologous tissue

Renewed interest in the use of aldehydes in endodontics has made it necessary to find out if the antigenic properties of foreign proteins can be attenuated by glutaraldehyde fixation. Untreated and glutaraldehyde-fixed heterologous tissue was, therefore, implanted in rabbits. The local tissue reaction to the implants as well as the reaction in the lymph nodes draining the implant site was examined. The experimental results do not support the view that glutaraldehyde fixation, in the long term,attenuates the antigenic properties of proteins.

The response of the living organism to dead and fixed dead enclosed homologous tissue

Polyethylene tubes at both ends and with four perforations in the side walls were filled with untreated homologous necrotic muscle tissue or formaldehyde-fixed or glutaraldehyde-fixed homologous necrotic tissue and implanted subcutaneously in rats. The cell reaction in the tissues surrounding the differently filled tubes was examined. It was found that the inflammatory reaction to untreated necrotic homologous tissue was the least severe.

Release of endotoxin in an experimental model simulating the dental root canal.

The action of endotoxin on subcutaneous connective tissue was examined in an experimental model simulating the dental root canal. The local Shwartzman reaction was used as a tool to detect slight tissue alterations that might otherwise go unobserved. The experimental results warrent, in our opinion, the tentative conclusion that the primary toxicity of endotoxins has no major part in the initiation or maintenance of chronic periapical inflammation.

Short-term tissue reactions to enclosed glutaraldehyde-fixed tissue

Polyethylene tubes closed at both ends and with four perforations in the sidewalls were filled with glutaraldehyde-fixed isologous tissue and implanted subcutaneously in rats. The cell reaction during the first 12 days in the tissues adjacent to the tubes was histologically examined. The reaction was compared to the reaction around tubes implanted empty. The examination showed a severe inflammatory reaction with probably immunologic aspects in the tissues adjacent to the filled tubes. The reaction around the empty tubes was slight and transient.

Basic Biological Sciences Root Canal-simulating Experimental Model for Evaluation of Tissue Responses to Chronic Influx of Foreign Fluid Substances

Searching for an experimental model simulating the root canal, a two-stage procedure was evolved using polyethylene tubes implanted subcutaneously in rabbits. The reaction to the model was histologically evaluated, and the rate of release of macromolecules from the tubes was studied using radio-labeled endotoxin and albumin. The model proved suitable for evaluating an animals tissue response to the slow and prolonged influx of foreign fluids.Searching for an experimental model simulating the root canal, a two-stage procedure was evolved using polyethylene tubes implanted subcutaneously in rabbits. The reaction to the model was histologically evaluated, and the rate of release of macromolecules from the tubes was studied using radio-labeled endotoxin and albumin. The model proved suitable for evaluating an animals tissue response to the slow and prolonged influx of foreign fluids.