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Biomedical subjects

J Silness

Publications and source records attributed to J Silness.

At least 37 records · Page 2Linked to original sources
PubMed1985

Marginal adaptation of resin veneers to gold castings.

The magnitude of the fissures between resin facing materials and gold castings was measured by light microscopy. Two different products and two different processing procedures were used. The effect of water sorption on the fissure size was also studied. Mean fissure sizes varied between 3 and 25 microns. The best adaptation between the resin material and the gold alloy was obtained by the conventional closed flasking technique compared with free processing in a pressure vessel. When processed by closed flasking the product that did not contain microfiller showed fissure widths approximately one fourth of those resulting from the open processing technique. The other product, containing microfiller, was less sensitive with regard to processing. The effect of water sorption on the fissure width was most evident in the test groups containing specimens processed in flask.

Chemical Phenomena↗
PubMed1985

Margin fit of metal crowns and bridge retainers.

The margin fit of metal crowns and bridge retainers was examined radiographically in individuals who were registered to receive treatment at the School of Dentistry, University of Bergen. One sample consisted of 184 individuals registered in 1967-68 and another one of 232 individuals registered in 1982-83. In all, 2057 proximal surfaces could be examined. The margin fit was scored as excess, deficit, or satisfactory. In the 1967-68 single-crown sample margin excess was recorded for 66%, margin deficit for 8%, and satisfactory fit for 26%, on the average. In the 1982-83 single-crown sample margin excess was recorded for 36%, margin deficit for 5%, and satisfactory fit for 59%. In the 1967-68 sample bridge retainer margins on the average scored 60% excess, 10% deficit, and 30% satisfactory fit. In the 1982-83 bridge retainer sample margin excess amounted to 33%, margin deficit to 4%, and satisfactory fit to 63%. The possible reasons for the differences between the two samples are discussed.

Aged↗
PubMed1985

Alveolar bone loss in bridge recipients after six and twelve years.

For a long time the major emphasis in prosthetic dentistry was placed on the technical and mechanical aspects of the different procedures and material used. The relationship between the prosthetic treatment and the periodontal tissues received less attention. As a consequence early results of epidemiological studies were not encouraging since they revealed that prosthetic treatment may be an important contributory factor in the aetiology of periodontal diseases. Research during the last two decades into the aetiology and pathogenesis of these diseases has revealed major principles and finer details relating to the mechanisms of their initiation and progression. Recent research has shown that cooperation between the prosthodontist and the periodontist, based upon agreed fundamental concepts, may give encouraging results in the prosthetic replacement of lost teeth. The study reported here assesses the effects upon the periodontal tissues of fixed bridges over a six and twelve year period.

Adult↗
PubMed1984

Effects on dental health of spacing of teeth in anterior segments.

The purpose of the study was to examine the relationship between spacing and dental health in 15-year-old adolescents. The whole sample consisted of 156 subjects. Out of them, 74 females and 73 males with 6 anterior teeth made up the study group for examination of the upper jaw. 75 females and 75 males had 6 anterior teeth in the lower jaw and made up the study group for examination of the lower jaw. The Plaque Index (PlI) and the Gingival Index (GI) were recorded. Probing depths (PD) were measured as explained by Glavind & Løe. Filled surfaces (FS) were taken from the individual case sheets and controlled clinically. The spacing of the individuals was assessed by counting the number of proximal surfaces without visible contact with the adjacent proximal surfaces, on model casts. The sum of proximal surfaces without contact made up the Space Index (SpI) of the individual jaw. Parametric and non-parametric statistical methods were used to analyze the data. In both sexes and both jaws proximal surfaces without interdental contact had a more favourable periodontal condition than surfaces with contact. In the upper jaw of both sexes, proximal surfaces without interdental contact had a reduced number of filled surfaces compared to surfaces with contact. The linear relationship between SpI and FS was significant, i.e., an increased number of surfaces without contact was accompanied by a reduced number of filled surfaces. In the lower jaw, the differences between the SpI groups and the linear relationship between SpI and FS did not reach significance. In both sexes and both jaws, proximal surfaces without fillings had a more favourable periodontal state compared to surfaces with fillings. Indications are that the summation effect of the presence of interdental contact and the presence of fillings contributed to the differences in periodontal condition between surfaces with and without interdental contact.

Adolescent↗
PubMed1982

The size of the Balkwill angle and the height of the Bonwill triangle.

The Balkwill angle and the height of the Bonwill triangle were measured on cephalograms of 128 adult females and males who had all their natural teeth. The size of the Balkwill angle was dependent on the choice of the condylar reference point, whereas the height of the Bonwill triangle was not. When analysed by sex, it was found that the Balkwill angle was larger in males than in females. Likewise, the height of the Bonwill triangle was larger in males.

Adult↗
PubMed1979

Distribution of corrosion products in teeth restored with metal crowns retained by stainless steel posts.

The nature and distribution of corrosion products in teeth restored with metal crowns retained by stainless steel posts were examined by means of energy-dispersive X-ray microanalysis, microradiography, and electron microscopy. The corrosion products consisted of calcium, phosphorous, iron, chromium, nickel, zinc, stannum and other elements. A possible root fracturing mechanism is discussed.

Corrosion↗
PubMed1978

The convergence angle in teeth prepared for artificial crowns.

The bucco-lingual and mesio-distal convergence angles in vital and rootfilled teeth prepared for complete crowns were measured microscopically on 190 stone dies. In vital teeth the mean convergence angles varied between approximately 19 and 27 degrees. In rootfilled teeth the mean angles varied between 12 and 37.

Crowns↗
PubMed1977

Preparation areas resisting displacement of artificial crowns.

The areas of luting cement resisting rotation of artificial full crowns subjected to non-axial forces were calculated for varying values of preparation diameter, height, and convergence angle. The calculations were performed for regular conical and pyramidal preparations. The results showed that the resisting areas are larger in pyramidal than in conical preparations. Increasing the convergence angle resulted in an almost linear reduction in resisting area. The reduction was particularly pronounced for preparations of large diameters.

Crowns↗
PubMed1977

Pilot study on dental erosion in a Norwegian electrolytic zinc factory.

In 12 workers in a Norwegian factory using electrolytic methods to extract zinc, a relationship was found to exist between degree of erosion, number of teeth affected and the length of service. The prevalence of caries, abrasion and attrition was not higher than in comparable population groups. The correlation between diagnosis of erosion based on clinical examination, and diagnosis based on evaluation of color slides was good.

Adult↗
PubMed1976

The occlusal fissure of unerupted third molars as an experimental caries model in man.

The aim of the present investigation was to establish an experimental model for the study of fissure caries development under conditions as similar as possible to the in vivo situation. Twenty-one blocks (2 X 2 X 3 mm) constituting part of the occlusal fissure were made from unerupted human third molars, and implanted for 60 or 90 d in mandibular molars of students. One milliliter of a 50% sucrose solution was applied to the fissures twice a day. After removal, sections were examined microradiographically in polarized light and in the electron microscope. As a control, the morphology and enamel structure of fissures from 10 unerupted third molars were studied. After 90 d a subsurface, radiolucent caries-like lesion was observed in two specimens only. When examined in air in polarized light, however, all sections exhibited caries-like lesions symmetrically located around the fissures. The 60-d material showed similar lesions, but not as frequently as the 90-d specimens. In the experimental material processed for electron microscopy revealed that the fissure plaque mainly consisted of cocci and small rods. Most often the bacteria were separated from the enamel surface by a pellicle.

Dental Caries↗