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Biomedical subjects

A Thylstrup

Publications and source records attributed to A Thylstrup.

At least 19 recordsLinked to original sources
PubMed1992

Results after 3 years of non-operative occlusal caries treatment of erupting permanent first molars.

The aim of the study was to describe the 3-yr results of a treatment program designed to control occlusal caries on the basis of intensive patient education and professional toothcleaning. The sample consisted of 56 children 6-8 yr old with their permanent right first molars in different stages of eruption. The results were compared with record data from 58 children of the same age who had received a traditional caries treatment program including fissure sealing (control group). After 1 yr a significant reduction of occlusal surfaces with visible plaque was noted in the study group as well as an increased proportion of arrested lesions. These results were maintained after 2 and 3 yr. Ten (9%) teeth were sealed and one filled during the study period. Examination of record data in the control group over a 3-yr period revealed that 76 (65%) first molars were sealed and 7 (6%) were filled. During the first year 1/3 of the children in the study group needed 5-6 recall visits, whereas in the following period all children were only seen 1-4 times. In contrast, 50% of the children in the control group needed 5-6 recalls in the 3rd yr. Our data indicate that professional care for erupting teeth on an individual basis has a long-term effect on occlusal surfaces as well. The alternative technique required less clinical time than the traditional application of sealants.

Child↗
PubMed1991

Results after 1 year of non-operative occlusal caries treatment of erupting permanent first molars.

The aim of this study was to evaluate a treatment program designed to control occlusal caries on the basis of intensive patient education and professional toothcleaning. The sample consisted of 56 6-8-yr-old children with their permanent right first molars in different stages of eruption. Data from the program were compared with previous data recorded in a similar sample of children. After 1 yr the majority of children in the study group had their permanent right first molars in full occlusion. A significant decrease of surfaces with easily detectable plaque and an increase of surfaces without plaque was observed. The proportion of arrested lesions increased and active enamel lesions decreased. Fissure sealing was only needed in two teeth in contrast to more than 2/3 of molars in a comparable sample of children. The program proved to be an efficient alternative to fissure sealing in preventing occlusal caries in erupting teeth.

Child↗
PubMed1991

Organic content in occlusal groove-fossa-system in unerupted 3rd mandibular molars: a light and electron microscopic study.

A method is described by means of which organic content in fissure areas of 12 unerupted 3rd mandibular molars can be prepared for studies in the light microscope (LM) and in the transmission electron microscope (TEM). Thus, LM and TEM examinations revealed that the organic content throughout the fissure in bone-covered and in mucosa-covered 3rd molars with uncompleted root formation consists of cells belonging to the enamel organ in late or in postmaturative stages. In mucosa-covered teeth with completed root formation it was only possible to identify enamel organ cells at the entrance of the fissure. Deeper parts were occupied by degenerative cells, polymorphonuclear cells and unidentified material. The results indicate that ameloblasts in fissures do not transform to stratified squamous epithelium but gradually degenerate towards terminal stages and remain as such, as the tooth emerges into the oral cavity.

Adolescent↗
PubMed1991

Light and transmission-electron microscopy study of enamel organ cells in germectomized human third mandibular molars.

Using nine serially sectioned germectomized mandibular third molars it was possible to examine light microscopical (LM) and transmission-electron microscopical (TEM) features of maturing human enamel organ cells. The degree of enamel mineralization was estimated by quantitative imbibition studies in polarized light. It was possible to distinguish between three progressive stages of enamel mineralization. The most advanced stage was characterized by external enamel porosity. In the least advanced stages the enamel porosity appeared more extensive beneath a less porous surface layer. Ruffle- and smooth-ended ameloblasts were identified corresponding to the maturing enamel. Smooth-ended ameloblasts were the most frequently observed. However, no preferences for one of the two cell types could be observed in relation to the different stages of enamel mineralization. The maturing human enamel organ cells broadly revealed the same characteristics with respect to morphology features, intracellular organization, and junctional complexes as described in the maturation zone of the rat incisor enamel organ. Our findings therefore add to the view that the basic pattern of amelogenesis is identical in human and rat incisor enamel.

Adolescent↗
PubMed1991

Morphometric analysis of occlusal groove-fossa-system in mandibular third molar.

Based on serially cut 200-microns-thick sections from 21 human mandibular third molars, a quantitative characterization was made of the morphology in the mesial and distal interlobal groove. Two parameters were used: depth of interlobal groove and structure angle. The interlobal groove depth varied between 0.13 and 0.55, taken in relation to the maximum crown height. The structure angle varied between 2 degrees and 170 degrees. If the structure angle was less than or equal to 25 degrees, the interlobal groove was classified as a fissure; if the angle was greater than 25 degrees, the interlobal groove was classified as a groove. Only in 18% of the sections did the interlobal groove manifest itself as a fissure. The study demonstrates that it was possible unambiguously to describe the two-dimensional profile of interlobal grooves by groove depth and structure angle.

Classification↗
PubMed1991

[Indications and use of fissure sealants in public dental health care in Denmark. A questionnaire-investigation].

During the past decade usage of the fissure sealant technique for occlusal caries prevention has been increasingly recommended. This study explores variations in indications and usage of this technique in Denmark. A questionnaire was sent to 205 chief dental officers in the Danish Public Child Dental Health Service (PDHS) covering 90% of Danish children and to municipalities, where dental health to children is provided by private practitioners. More than half of the respondents did not use firmly defined criteria for fissure sealant application. Oral hygiene and previous caries experience were most often stated as indications. Actual usage of the sealant technique differed significantly from the PDHS and private clinics. Thus, 33% of the chief dental officers in the PDHS said that sealants were routinely applied to 8- and 13-year-olds, 43% to 30-80% of the children, and 15% used sealants to less than 10% of 8- and 13-year-olds. In contrast, only 5% of the private clinics reported routinely use of sealing technique, 22% used application to 30-80% of the children, while more than one third of the private practitioners used sealants to less than 10% of the 8- and 13-year-olds. In spite of the significant difference in sealant usage between PDHS and private practitioners, it was not possible to see a corresponding difference neither in caries prevalence nor in occlusal filling incidence. Moreover, analysis of PDHS caries prevalence data revealed that PDHS variations could not be explained by variations of risk in terms of social classes and caries incidence.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1979

Evaluation of a pit- and fissure-sealing program in a public dental health service after 2 years.

The aim of the present study was to test the caries-preventive effect of a bis-GMA type fissure sealant (Concise Enamel Bond System) in a public dental health service for children. The study compared one group of children, in which all sound permanent teeth were sealed, and a control group in which no sealants were placed. During the study period all children received systematic restorative care, while sealing was performed on the basis of diagnoses made at subsequent examinations by one of the authors. After 2 years a total of 187 children were available for re-examination. Sealant retention was comparable to that obtained in previous studies, but no statistically significant reduction in overall caries increment could be demonstrated. Further analysis showed that only 223 sites had been sealed, while the majority of all erupting sites (394) were either carious or filled before they were screened for the purpose of sealing. It is therefore assumed that only teeth less susceptible to occlusal decay were sealed, thereby explaining the lack of benefit derived from the sealing program.

Child, Preschool↗
PubMed1979

Effect of long-term administration of fluoride on plasma fluoride and calcium in relation to forming enamel and dentin in rats.

Three groups of 1-month-old rats were kept on water containing 0.2, 56.5 and 113 parts/10(6) F-, respectively, for a period of 2 months. These groups were set up in order to study the relationship between long-term administration of high doses of waterborne fluoride, plasma values of fluoride and calcium and changes in forming dentin and enamel of the rat incisor. The microradiographic study revealed that increased levels of fluoride caused a delay in mineralization of the enamel. In the 113 parts/10(6) group the radiolucent areas in the enamel exhibited a distinct periodicity along the tooth, a phenomenon which cannot at present be explained. In the dentin the fluoride interfered with the process of mineralization giving rise to radiolucent and radiopaque banding in the experimental groups. With increasing levels of fluoride in the water supply a significant increase of plasma fluoride was recorded. In contrast the serum calcium values in both experimental groups were reduced to the same extent, which differed significantly from that of the control group. It is concluded that the fluoride doses which are needed to create fluorotic changes in rats may interfere with calcium metabolism and basic mineralization processes.

Amelogenesis↗
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↗