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Biomedical subjects

D Orstavik

Publications and source records attributed to D Orstavik.

At least 73 records · Page 4Linked to original sources
PubMed1983

Effects of therapeutic and pulp protecting materials on nerve transmission in vitro.

Effects of therapeutic and pulp protecting dental materials on nervous tissue were studied in an in vitro model utilizing the isolated left rat phrenic nerve. The nerve was placed in a buffer bath between two suction electrodes, one for electrical stimulation and one for recording. Evoked compound action potentials (cAP) were monitored in an oscilloscope. Fresh mixes of six commonly used pulp-dentin materials were placed in contact with the nerve, and the cAP registered. Formocresol, zinc oxide-eugenol (ZOE), Calasept and Dycal caused a complete depression of the nerve activity within 0.5 to 5 min of contact. The depression appeared irreversible with Formocresol and Calasept, reversible with Dycal, and reversible with ZOE when applied to nerves surrounded by adherent fatty tissue. De Trey Zinc and Durelon caused only a minor depression of the cAP within 30 min of contact.

Action Potentials↗
PubMed1983

Weight loss of endodontic sealers, cements and pastes in water.

A solubility test based on weight loss in water, as proposed for standard testing programs (ADA & ISO), was adapted for assessing the solubility of 10 root canal sealers, cements and pastes. The weight loss of the set materials during 24 hr in distilled water at 37 degrees C ranged from -0.84 (AH26) to 22.71 (Kloroperka N-O) weight per cent. The results were reproducible, and the test was considered suitable for routine testing of weight loss in water of endodontic materials. However, the test may not provide information which is directly related to the clinical behavior of the materials.

Chemical Phenomena↗
PubMed1982

Neurotoxic effects of root filling materials on rat phrenic nerve in vitro.

Inhibitory effects of root filling materials on the conduction of action potentials evoked in rat phrenic nerves were evaluated in vitro. Endomethasone and N2 Normal completely and irreversibly inhibited conductance; ProcoSol caused complete but reversible inhibition; Kloroperka N-O caused total inhibition which was sometimes reversed; and AH26 and Diaket showed partial inhibition which was partially reversible.

Action Potentials↗
PubMed1982

Preferential affinity of oral bacteria for homologous salivary films on dental materials.

Freshly isolated strains of Streptococcus mutans from saliva of two test subjects were tested for adhesion to various dental gold alloys and one brand of luting cement. The materials were covered with pellicle derived from one or the other of the two subjects. In "crossover" experiments it was consistently found that S. mutans adhered in greater numbers to pellicles of homologous origin. This preference for the homologous pellicle appeared to vary among the materials tested as substrates; also, the total number of organisms adhering varied among the materials. Moreover, different isolates varied in their affinity for the materials and showed a varying degree of dependence on homologous pellicle for adherence. In vitro plaque formation of mixed oral flora on pellicle-coated dental casting gold alloy were also more abundant on homologous pellicles as compared with heterologous ones. The results support the view that biologically specific mechanisms contribute to the adhesion of bacteria to dental restorative materials, and to the build-up of a bacterial plaque on these materials.

Adhesiveness↗
PubMed1982

Influence of in vitro propagation on the adhesive qualities of Streptococcus mutans isolated from saliva.

Streptococcus mutans from saliva of one test person were isolated on mitis/salivarius agar containing bacitracin and extra sucrose, and subcultured in vitro on trypticase soy broth with numerous transfers. Freshly isolated organisms and bacteria from selected subcultures were studied in adhesion tests using glass or dental zinc phosphate cement as substrate. Different bacterial isolates were used in separate experiments. Three different techniques were used; two based on radioactivity assays of adhering 3H-thymidine-labelled bacteria, and one based on visual counting. With all three techniques freshly isolated S. mutans adhered in significant numbers. It was consistently found that their ability to adhere decreased with the number of in vitro transfers. The results support the view that growth condition is an important factor governing the adhesive properties of oral bacteria.

Adhesiveness↗
PubMed1982

Tooth colored dental restorative materials: porosities and surface topography in relation to bacterial adhesion.

The present investigation was carried out to determine whether differences in initial bacterial accumulation on dental restorations could be explained by differences in surface topography, particularly porosities, of the materials. A point counting method was used to determine the number and the size of the porosities in 15 materials. The results demonstrated great variation among the materials in the number of porosities. However, in vitro bacterial adhesion tests failed to show any relationship between porosities in the materials and the number of bacteria adhering to them. Nor were differences in surface topography, as measured profilometrically, associated with differences in bacterial adhesion. It is concluded that variations in surface topography including porosities do not suffice to explain differences in initial bacterial accumulation on silicate cements and composite dental restoratives.

Adhesiveness↗
PubMed1981

Radiopacity of root canal sealers.

A standardized and reproducible method of radiopacity measurements of dental materials is presented. The method entails densitometric comparison of standard-sized specimens with an aluminum step wedge under controlled conditions for exposure and film processing. Methodologic aspects have been evaluated and discussed. Measurements of forty root canal sealers demonstrated wide variations among the different types. Visual examination could not provide reproducible measurements of the radiopacity of the materials.

Absorptiometry, Photon↗
PubMed1981

Two-hour bacterial colonization of dental luting cements in vivo.

Test specimens of zinc phosphate, polycarboxylate, zinc oxide-EBA, silico-phosphate and resin cements were carried in the mouth for 2 hours. The bacteria adhering to the cement specimens were quantified after culture on selective and non-selective, solid media. Significantly fewer bacteria could be recovered from the EBA cement than from the other cement types. All cement specimens, as well as samples from tooth surfaces, showed selective enrichment of Actinomyces viscosus compared with the proportion of this organism in saliva. The silicophosphate and particularly the polycarboxylate cement were poor substrates for the adhesion of Streptococcus mutans. Scanning electron micrographs revealed heavy accumulations of coccoid and filamentous organisms on zinc phosphate cement surfaces. Fewer bacteria, mainly cocci, were seen on the polycarboxylate and silico-phosphate cements, whereas the micrographs of the EBA and resin cement surfaces were difficult to interpret.

Actinomyces↗
PubMed1981

Bacterial growth on dental restorative materials in mucosal contact.

Test specimens of amalgam, gold, porcelain, heat-cured acrylic resin, and human enamel were made to fit into cavities prepared in acrylic pontics of maxillary bridges. One side of the specimen was in close contact with the mucosa. Plaque was allowed to accumulate on the specimens for 27 to 48 days, and adherent bacteria were then quantified by cultivation on selective and non-selective media. The inflammatory status of the mucosa overlying the specimens were monitored by exudation measurements. Lower total numbers of bacteria were recovered from acrylic specimens than from the other materials used, including enamel. There were also significant subject differences in bacterial recovery. Test specimens in contact with inflamed mucosa yielded less total numbers of bacteria, but higher numbers of Streptococcus mutans, than did specimens exposed to mucosa with no or negligible exudation.

Acrylic Resins↗
PubMed1980

An in vitro model for studying adsorption of oral streptococci to crown and bridge cements.

A sensitive, in vitro method has been developed for the study of bacterial adsorption to dental crown and bridge cements. The method employs heavily radiolabelled cells which adhere to the wall in wells made from the cements. Loss of radioactivity from the bacterial suspension during incubation is used to measure the degree of bacterial adherence to the materials. Strains of Streptococcus sanguis and Streptococcus mutans adhered in greater numbers than a strain of Streptococcus salivarius to both a zinc phosphate cement and a zinc carboxylate cement. The zinc phosphate cement supported adherence to a greater degree than did the zinc carboxylate cement. Pretreatment of the cement surfaces with human saliva tended to reduce bacterial adherence. Pretreatment of the bacteria with saliva slightly enhanced sorption of S. sanguis and S. salivarius, but tended to impair sorption of S. mutans to both types of cements. When both bacteria and cements had been pretreated with saliva, a strong inhibition of the adherence of S. mutans was observed.

Adhesiveness↗
PubMed1979

Effects of bactericidal treatments on bacterial adherence and dental plaque formation.

In vivo plaque formation was significantly reduced when tooth surfaces were subjected to topical applications of iodine (0.2% I2 in 2.0% KI) twice daily for 3 d. Similarly, in vivo plaque formation was significantly reduced on enamel surfaces that were subjected to ultraviolet irradiation. Control experiments indicated that neither ultraviolet irradiation nor iodine treatment interfered with mechanisms for bacterial apposition to dental plaque. The results are interpreted to suggest that plaque grows in mass primarily by the division and multiplication in situ by plaque bacteria, not by a continued apposition of salivary microbes.

Adhesiveness↗
PubMed1978

Antibacterial activity of tooth-colored dental restorative materials.

The antibacterial activity of dental restorative materials (12 resin based and one silicate) was tested in vitro against 5 species of bacteria. When fresh, all materials inhibited growth in pour plates of at least one bacterial strain. After storage in saline for 24 hours, the antibacterial activity was markedly reduced. There was a wide variation among the materials in the extent of their antibacterial activity. The bacterial strains apparently differed in their susceptibility to the antibacterial activity of the materials.

Anti-Bacterial Agents↗
PubMed1978

Bacterial adherence related to agglutination and surface film formation.

1) Film formation on glass and enamel surfaces tended to reduce the sorption of streptococci to these surfaces. When solutes with affinities for the test bacteria were used to produce the surface film, bacterial sorption to that surface was greater than to surfaces coated by indifferent solutes. 2) Streptococci in small aggregates sorbed to glass and enamel in numbers comparable to, of greater than, unaggregated cells. When the test suspension showed visible clumping, sorption was markedly impaired.

Adhesiveness↗
PubMed1977

Some antibacterial properties of periodontal dressings.

Three commercial periodontal dressings were tested for antibacterial activity against salivary microorganisms after having been stored dry or in liquid for 1 and 2 days. Inhibition of growth of mixed salivary flora was evaluated on blood agar dishes. Also, the ability of Strep. mutans to colonize the surface of the dressings was tested. The surface contact test indicated antibacterial activity against salivary microorganisms by freshly made Coe-pak and Wondrpak. Some activity could also be observed after 2 days' storage in about half the experiments. The initial bacteriostatic effect of Peripac was limited to the setting phase. The plaque accumulation test revealed single cells only on the surfaces of Coe-pak and Wondrpak whereas Peripac seemed to be colonized by the test bacteria.

Bacteriological Techniques↗