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Biomedical subjects

A Thylstrup

Publications and source records attributed to A Thylstrup.

At least 91 records · Page 5Linked to original sources
PubMed1979

A scanning electron microscopic and microradiographic study of pits in fluorosed human enamel.

The aim of the present study has been to correlate the surface appearance of pitted, fluorosed enamel in the scanning electron microscope (SEM) with the microradiographic features of the underlying tissue. Intact enamel surfaces of severely fluorosed teeth appeared similar to that of normal enamel. In the unabraded surfaces discrete pits were sharply demarcated from the surrounding intact enamel surface leaving steep walls of parallel running rods. The microradiographic appearance of sections made through pits indicated that focal loss of surface enamel occurred corresponding to the inner highly hypomineralized part of the fluorotic subsurface lesion. The abrupt wall formation and the finding that the striae of Retzius never changed direction along the margins of the lesions indicated that pits in fluorosed enamel may be secondarily produced defects rather than true hypoplasias. Further evidence of the posteruptive origin of the defects was derived from the observation that enamel lamellae occasionally formed part of the lateral border. The relatively higher degree of radiopacity observed in the tissue surrounding the pit indicates a posteruptively acquired deposition of minerals in the exposed porous enamel.

Dental Enamel↗
PubMed1979

A scanning electron microscopical study of normal and fluorotic enamel demineralized by EDTA.

Normal and fluorotic primary and permanent teeth were demineralized in 10% EDTA at pH 7 for varying periods of time up to 4 weeks. The fluorotic teeth initially dissolved at a much slower rate than non-fluorotic specimens and appeared to contain more organic material. After almost complete removal of the outer enamel a soft organic layer remained on the dentin surface. This consisted of a fine fibrillar mesh and some more dense material. After four weeks much of the organic material had disappeared leaving only a thin membrane on the dentin surface.

Dental Enamel↗
PubMed1979

A scanning electron microscopical study of normal and fluorotic enamel demineralized by EDTA.

Normal and fluorotic primary and permanent teeth were demineralized in 10% EDTA at pH 7 for varying periods of time up to 4 weeks. The fluorotic teeth initially dissolved at a much slower rate than non-fluorotic specimens and appeared to contain more organic material. After almost complete removal of the outer enamel a soft organic layer remained on the dentin surface. This consisted of a fine fibrillar mesh and some more dense material. After four weeks much of the organic material had disappeared leaving only a thin membrane on the dentin surface.

Dental Enamel↗
PubMed1978

Clinical appearance of dental fluorosis in permanent teeth in relation to histologic changes.

Based on studies in Northern Tanzania a new classification system of dental fluorosis is proposed. The classification system includes 10 scores designed to characterize the degree of dental fluorosis affecting buccal/lingual and occlusal surfaces. With aid of polarized and ordinary light microscopy the histologic features behind the individual scores are described. The macroscopic appearance of increasing degrees of dental fluorosis were well correlated to the degree of subsurface porosity. Above a certain level of subsurface hypomineralization various degrees of loss of surface enamel occurred, presumably as a result of posteruptively acquired injuries. Application of the new classification system to samples of children born in areas with 3.5, 6.0 and 21.0 parts/10(6) F- in the water supplies revealed that the distribution of dental fluorosis within the individual followed the same pattern irrespective of fluoride concentration in the water. While the classical Dean index was unable to distinguish between dental fluorosis in the 6.0 and the 21.0 parts/10(6) area it was possible with the new system to disclose that particularly the posterior teeth were significantly more affected in the latter area. Comparisons of degree of dental fluorosis with available measurements of enamel thickness proved that the within-tooth as well as within-dentition variations are determined by enamel thickness rather than length of exposure to body fluids. The limitations of the Dean index are discussed with special attention to its validity as a biological index in relation to current efforts to determine the minimal toxic effect of fluoride on the dental hard tissues.

Adolescent↗
PubMed1978

Distribution of dental fluorosis in the primary dentition.

By the use of a new classification system of dental fluorosis, primary and permanent teeth were examined in samples of children born in areas with 3.5, 6.0 and 21.0 parts/10(6) F- in the water supplies. The severity of dental fluorosis was lower than in the corresponding permanent teeth, but a significant increase in severity was noted with increasing concentration of fluoride in the drinking water. The distribution of dental fluorosis within the dentition followed the same pattern irrespective of fluoride content of the water. Thus, a progressive increase in severity was noted from the anterior to the posterior teeth. This pattern is presumably determined by variations in enamel thickness. The much thinner enamel layer of primary teeth may also explain the lower degree of dental fluorosis in these teeth rather than a maternal barrier to fluoride. The degree of dental fluorosis observed in medium and high fluoride areas did not support the hypothesis that the rapidly growing skeleton of infants prevents fluoride-derived enamel changes.

Adolescent↗
PubMed1978

Retention and effectiveness of a chemically polymerized pit and fissure sealant after 2 years.

Following a single application of a chemically polymerized fissure sealant (Concise Enamel Bond System) 60% of the sealants were present after 2 years of examination. The effectiveness of the treatment was highly significant and the caries reduction, irrespective of the sealant status, was found to be about 50%. The caries reduction was 98% in sealed pairs where the material was fully retained.

Child↗
PubMed1977

The influence of traumatic intrusion of primary teeth on their permanent successors in monkeys. A macroscopic, polarized light and scanning electron microscopic study.

Primary maxillary and mandibular central incisors were experimentally intruded on 13 monkeys, in order to examine changes of the enamel in the permanent successors. To study the effect of removal of the displaced tooth, the left primary incisor was extracted 1 h after the trauma, whereas that on the right was left in the jaw. Six weeks later the animals were sacrificed. Macroscopically, circumscribed areas of opacities on labial enamel were noted. The SEM examination showed that non-affected parts of enamel had reached anatomical form, whereas inhibition studies and microradiographs demonstrated that the maturation process was far from complete. Arrest of enamel maturation was noted as corresponding to the extent of the surface opacity. In the SEM small areas displaying rupture of the surface enamel were seen. No differences were observed either macroscopically or histologically in relation to immediate removal or preservation of the intruded primary incisor.

Animals↗
PubMed1977

Surface structure of tooth germs from newborn infants: a light and scanning electron microscopical study.

Tooth germs from the mandibles of 5 stillborn infants were examined by scanning electron microscopy and light microscopy in order to investigate the surgace structure at different stages of mineralization. The surface of the completed enamel of the incisal third of the incisors was smooth, indicating that amelogenesis was at an end. The interface relief between ameloblasts and enamel matrix on the remaining part of the incisors, and on the forming cusps, was characterized by numerous deep pits caused by the Tomes' processes of the ameloblasts. When parts of the organic matrix were removed by sodium hypochlorite, the crystals were exposed as needle-shaped structures. Towards the bases of the cusps the pits gragually smoothed out, continuing as a narrow even surface zone corresponding to the first formed aprismatic enamel. In this zone circular holes 1 micronm were encountered which the light microscope studies showed were dentinal tubules passing into the enamel. At the bases of the cusps there was a rather abrupt demarcation toward a surface zone exhibiting countless slender villi. The light microscope observations indicated that these villi represented the first formed dentine after the basement membrane had disappeared.

Amelogenesis↗
PubMed1976

Retention and effectiveness of a chemically polymerized pit and fissure sealant after 12 months.

The aim of the present study was to evaluate the retention and effectiveness of a bis-GMA type of fissure sealant which polymerizes after conventional mixing of the two catalyst/activator components (Concise Enamel Bond System). Unilateral sealing of homologous pairs of permanent first molars was carried out by a dental hygienist. Of the 451 sealed sites sealant was present in 73%, partly missing in 8%, and completely missing in 18% after 1 year. The effectiveness of the treatment in preventing occlusal caries was highly significant and the caries reduction was found to be about 70%. A strong relationship between status of sealant and occlusal decay was demonstrated. The shortcomings of the half-mouth design when evaluating sealants as a caries-preventive measure in public dental health programs are discussed.

Child↗