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Biomedical subjects

O Fejerskov

Publications and source records attributed to O Fejerskov.

At least 181 records · Page 10Linked to original sources
PubMed1977

Surface etching and subsurface demineralization of dental enamel induced by a strong acid.

Intact enamel surfaces were exposed to 20 ml of 0.1% HCl for various periods. When the acid was unsaturated with respect to both hydroxyapatite and fluorapatite the surface enamel was etched away. With time the liquid close to the enamel became supersaturated with respect to fluorapatite but remained unsaturated with respect to hydroxyapatite. Under this condition subsurface lesions developed. These observations are discussed with reference to the use of diffusion-restricting agents in laboratory caries experiments.

Acid Etching, Dental↗
PubMed1977

Clinical, histological and ultrastructural features of a possibly virus-induced oral leukoplakia.

Two male patients with oral leukoplakias exhibiting a peculiar type of apparent dysplastic changes have been followed for 4 and 6 years, and a series of biopsies have been examined by light and electron microscopy. The apparent lack of normal epithelial stratification below the keratinized cell layers was mainly caused by the frequent appearance of large ballooned cells and multinuclear giant cells. The centre of the large ballooned cells contained aggregations of chromatin and evenly-dispersed microtubulus surrounded by a thick rim of tonofibril bundles. In the peripheral cytoplasm large numbers of smooth-surfaced endoplasmic reticulum were found, but no Golgi apparatus was observed. In addition, several autophagocytic bodies were recorded. Along the cell membrane only a few desmosomes were present, whereas aggregations of digested desmosomes were found in the cytoplasm. On the basis of the ultrastructural findings, it is suggested that the large ballooned cells represented epithelial cells arrested in early stages of mitotic division. The epithelial cells in interphase exhibited a normal ultrastructure except for large nucleoli with varying degrees of condensation of nucleolonema and vacuolization. Further, atypical dense granular aggregations and strands of fine fibrillar material were recorded in the nuclei. It is suggested that this new type of oral leukoplakia has a viral etiology.

Aged↗
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

Clinical, radiologic, and histopathologic aspects of 13 cases of nevoid basal cell carcinoma syndrome.

Thirteeen patients with the characteristic signs and symptoms of the nevoid basal cell carcinoma syndrome (NBS) are presented. It is suggested that the chromosomal anomalies sporadically reported have hardly any connection with the syndrome. The jaw cysts removed from the patients with NBS were clinically, radiologically, and histopathologically typical keratocysts with a high occurrence of epithelial islands and/or microcyts in the connective tissue of the capsule. The significantly higher occurrence of proliferative epithelial remnants in the connective tissue of the cyst wall may be an explanation of the high recurrence rate seen in patients with NBS and of the recurrence of some solitary keratocysts in patients without any signs or symptoms of NBS. In a follow-up period of 2 years, 85% of the patients with NBS showed recurrence. One-third of these patients did not show any recurrence at the 1-year follow-up. Therefore, a follow-up period of 2 years or more is mandatory in the care of patients with the nevoid basal cell carcinoma syndrome.

Adolescent↗
PubMed1976

Ultrastructure of epithelial lining of keratocysts in nevoid basal cell carcinoma syndrome.

The ultrastructure of the epithelial lining of 12 odontogenic keratocysts in nevoid basal cell carcinoma syndrome was investigated. The differences in fine structure between normal keratinizing squamous epithelium of skin or mucous membrane and keratocyst epithelium are discussed. It is demonstrated that separation of keratocyst epithelium from the underlying fibrous capsule is due to fragmentation and partial or complete disappearance of collagen in the juxtapithelial connective tissue compartment. Collagenolytic activity is suggested as a probably mechanism for this phenomenon.

Adolescent↗
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↗
PubMed1976

Polarized light microscopy of enamel structure in incisors from newborn infants.

Enamel structure in human primary incisors was histologically examined in order to compare the observations with those from recent studies on incipient carious and fluorosed enamel. Ground sections from mandibular incisors of five full-term human infants were examined in polarized light using aqueous media (water, Thoulet's media), alcohols with different refractive indices, and quinoline. Imbibition graphs were made along traverses from the amelodentinal junction (ADJ) to the enamel surface. Quantitative assessments of the birefringence in different media along the traverses indicated a change in the relative volumes of crystallites and surrounding medium with a continuous growth of crystallites toward the ADJ. The influence of organic material is discussed in relation to the differences in calculated form birefringence observed within the specimens. When examined in quinoline, a 30-40-mum-thick surface zone appeared distinct positively birefringent, indicating that the outermost enamel reacted as a molecular sieve. Because of the lower content of minerals the interpretation of this zone differed from that of similar "dark zones" observed in carious and fluorosed enamel.

Dental Enamel↗
PubMed1975

Oral giant cell granulomas. An ultrastructural study of the vessels.

Eight peripheral and 2 central oral giant cell granulomas have been studied in the electron microscope in order to examine the structure and nature of the vessels. The vascular wall was composed of a continous layer of endothelial cells resting on a basal lamina, which was frequently multilayered. The lamina also surrounded scattered subjacent pericytes. The endothelial cells overlapped slightly so as to form narrow intercellular spaces. Based on these observations the vessels are supposed to be postcapillary venules. Dark cells exhibiting degenerative features were encountered in the endothelial lining of most vessels. Small gaps and larger defects in the vascular lining allowed direct continuity between the lumen and the perivascular tissue. It is suggested that the extreme extravasation of red blood cells frequently observed in oral giant cell granulomas may be mediated through this incomplete lining.

Blood Vessels↗