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L Tronstad

Publications and source records attributed to L Tronstad.

At least 19 recordsLinked to original sources
PubMed1992

The end of an era.

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History, 20th Century↗
PubMed1992

Profiling of Propionibacterium acnes recovered from root canal and blood during and after endodontic treatment.

This report describes the first results of an ongoing study of bacteremia after endodontic treatment of teeth with Asymptomatic apical periodontitis. After access cavity preparation, microbiological samples were taken from the root canal under aseptic conditions in 4 single-rooted teeth in 4 patients. In treatment of 2 of the patients, the first 3 reamers (sizes 15-25) were deliberately used to a level 2 mm beyond the apical foramen. In 2 patients the instrumentation ended inside the root canal 1 mm short of the apical foramen. Blood samples were taken from the patients during the endodontic instrumentation and 10 min after the treatment was completed. Using lysis-filtration under anaerobic conditions, the blood was passed through a cellulose membrane filter. The filters as well as the root canal samples were incubated using an anaerobic technique. Anaerobic bacteria were isolated from all root canals. In the 2 patients where overinstrumentation had occurred, Propionibacterium acnes was recovered both from the root canals and from the blood samples taken during and after the treatment had been completed. Biochemical profiles, antibiotic susceptibility tests and electrophoresis of soluble proteins revealed that Propionibacterium acnes isolated from the root canal and blood samples were identical within patients, but varied between patients. Facultative anaerobic bacteria including Streptococcus sanguis were recovered from only one root canal sample and not from the blood samples.

Adult↗
PubMed1979

A method for toxicity screening of biomaterials using cells cultured on millipore filters.

In the present paper a tissue culture technique is described whereby the toxicity of setting and solid materials may be evaluated. A cell monolayer was established on a millipore filter which was placed on an agar medium, cell side down. Test specimens were placed on top of the millipore filter and were allowed to influence the cells through the filter for two hours. The cell reaction was assessed by incubating the cells, still adherent to the filter, for the demonstration of succinate dehydrogenase activity. Materials with a cytotoxic effect caused a zone of inhibited enzyme activity in the cell-material contact area. The filters were examined macroscopically and scores from 0 to 3 were given to grade the severity of the cell response. Unset and set silicate cement, zinc phosphate cement and an acrylic resin were tested. The results obtained were consistent and in accordance with those of previous reports. The method was simple and rapid and appeared suitable for the assay of larger test series.

Animals↗
PubMed1978

Vital staining of coronal dentin in monkey teeth.

Vital staining of monkey incisor teeth with the incisal dentin exposed to the oral environment by attrition was carried out, with the use of a number of dyes (pH and redox indicators). There was a distinct staining of the coronal dentin, regardless of which dye was introduced into the pulpal cavity. The exposed dentin was stained like the unaffected dentin, with the exception of a narrow centrally located zone that extended from the tip of the original pulp horn to the incisal edge of the tooth. The suggestion is that this zone is not unstained because of exposure of the dentin to the oral environment, but because it coincides with an area of the tissue where the pulpal ends of the dentinal tubules are blocked by atubular hard tissue normally laid down in the pulp horn of incisor teeth.

Animals↗
PubMed1978

Tissue reactions following apical plugging of the root canal with dentin chips in monkey teeth subjected to pulpectomy.

The tissue reaction following apical plugging of the root canal with dentin chips in monkey teeth subjected to pulpectomy was studied. The reaction was characterized by formation of a cementum-like tissue onto the chips, often walling off the root canal as well as accessory and lateral canals. Twenty-two of twenty-four teeth were rated as successful 95 days after pulpectomy. In the control groups, in which apical plugging of the canal with dentin chips was not attempted, ten of twenty-one teeth were rated as successful at this observation time. In six of the ten successfully treated teeth in these groups a dentin chip plug had been made, although care had been taken to avoid this. It is suggested that a plug of dentin chips is well tolerated by the tissues and may present an effective barrier in the apical part of the root canal, facilitating the accomplishment of a well-condensed, tightly sealing root filling.

Animals↗
PubMed1978

A microangiographic study of vascular changes in replanted and autotransplanted teeth of young dogs.

The purpose of the present investigation was to study the revascularization process of the pulp of replanted and autotransplanted teeth with incomplete root development in dogs. A barium-sulfate injection method combined with contact microradiography was used. Ingrowth of apparently new vessels was seen during the first postoperative days. After 10 days, visible vessels were seen in the apical half of the pulp, and after 30 days, in the whole pulp. Branches and apparently also anastomoses between pulpal vessels were seen after 10 days but were especially numerous after 30 days. One hundred eighty days postoperatively, only one of fifteen teeth was devoid of visible vessels, indicating pulpal necrosis. Thirteen of the remaining fourteen teeth exhibited visible vessels throughout the entire length of the pulp. It seems, therefore, that replanted and autotransplanted teeth with open apices have a high potential for repair. The revascularization of the pulp appeared to occur mainly by ingrowth of new vessels. In some instances, however, anastomoses seemed to form to pre-existing vessels in the pulp.

Animals↗
PubMed1978

A method for evaluation of initial tissue response to biomaterials.

In the present paper an implantation technique is described whereby the effect of the surgical operation is eliminated and initial tissue reactions to materials may be studied. A teflon body was implanted intramuscularly in rabbits. After six weeks the overlaying tissue was excised and the implant removed. An intact, nonepithelialized tissue surface was exposed, which due to the shape of the implant showed three indentations. Materials were placed in the indentations for 15 minutes and the tissue reaction was registered by enzyme histochemical methods. Silicate cement, zinc phosphate cement and a 4% phenol solution caused an inhibition in the dehydrogenase enzyme activity in the tissue subjacent to the indentations. The severity of the tissue reaction, indicated by the width of the inhibition zone, varied among the test materials. Silicate cement caused the widest inhibition zone and the phenol solution the narrowest one. These results correlate well with previous tissue compatibility studies and indicate that the method is applicable for in vivo screening of initial tissue response to biomaterials.

Animals↗
PubMed1977

An attempt to correlate dentin and pulp changes in human carious teeth.

The purpose of the present investigation was to study the dentin and pulp changes in the two halves of bisected carious teeth in order to determine if they are comparable. The dentin was studied by means of contact microradiography. Hypo- and hypermineralized zones, which were fairly similar in extension and degree of mineralization, were seen in the primary dentin of both halves of the teeth. If secondary dentin had formed, comparable amounts were usually present in the two halves. The pulp was studied, using demineralized 5 mum thick paraffin serial sections. In teeth with deep carious lesions severe inflammation with abscess formation was often observed in one half, whereas only scattered inflammatory cells were present in the other half. It seems questionable, therefore, whether the study of dentin and pulp reactions to caries in different halves of bisected teeth is a suitable method in investigations concerning a possible correlation between these reactions.

Dental Caries↗
PubMed1977

Enzyme activity in the pulp following preparation of cavities and insertion of medicaments in cavities in monkey teeth.

The effect of cavity preparation, calcium hydroxide and a corticosteroid on pulpal enzymes (Alkaline phosphatase, acid phosphatase, beta-glucuronidase, cytochrome oxidase and succinate, lactate and glucose-6-phosphate dehydrogenase) in monkey teeth has been studied by histochemical means. Cavity preparation with an air turbine and sufficient spray apparently did not affect the enzyme activity of the pulp, nor did application of a corticosteroid to the cavity floor. Twenty-four hours after calcium hydroxide application an increase in enzyme activity was found in the ondontoblastic and subodontoblastic cell layers subjacent to the calcium hydroxide-covered dentin. This activity seemed to demonstrate an onset of dentin formation, and 15 days after the application a slight amount of secondary dentin was found subjacent to the cavities in these teeth.

Acid Phosphatase↗
PubMed1977

The boss.

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Dentists↗
PubMed1976

Morphologic and enzyme histochemical observations on the pulp of human primary molars 3 to 5 years after formocresol treatment.

The state of the pulp of twenty-seven primary teeth treated by formocresol pulpotomy (clinically and radiographically successful) was assessed 3 to 5 years after treatment. A wide variation was found in the pulpal condition, from normal pulp tissue to total necrosis. Resorption and apposition of hard tissue were common findings. Five teeth were freeze-sectioned and incubated for histochemical demonstration of oxidative enzymes. The pulps of two teeth were vital; two teeth had necrotic areas subjacent to the amputation paste; and one pulp was totally necrotic. Six teeth were extracted 5 minutes after formocresol pulpotomy and incubated for demonstration of oxidative enzymes. An unstained zone, 1 to 2 mm. deep, was seen in all incubated sections. In conclusion, it seems that the formocresol method should be regarded only as a means to keep primary teeth with pulp exposures functioning for a relativley short period of time.

Dental Pulp↗
PubMed1976

Biological tests on an experimental glass ionomer (silicopolyacrylate) cement.

The biological compatibility of an experimental glass ionomer (silicopolyacrylate) cement has been assessed in in vitro (cell culture) and in vivo (monkey teeth) tests. For comparison a conventional silicate cement (Super Syntrex) was included in the in vivo experiments. In vitro, the glass ionomer cement was toxic when freshly prepared. The toxicity decreased, however, with increasing setting time. In experiments with prolonged cell-material contact time with specimens which had set for 24 h, the material appeared to be non-toxic. The in vivo experiments confirmed previous reports concerning unfavourable pulp reaction caused by silicate cement, while the glass ionomer cement caused mainly a mild pulp reaction after 8 days of observation. Unfortunately no longer-term observations were obtained since the material had been washed out of the cavities within 36 days.

Acrylates↗