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Biomedical subjects

O Fejerskov

Publications and source records attributed to O Fejerskov.

At least 109 records · Page 6Linked to original sources
PubMed1988

Dental fluorosis in the primary and the permanent dentition in fluoridated areas with consumption of either powdered milk or natural cow's milk.

The aim of the present study was to describe the patterns of dental fluorosis in the primary and the permanent dentition of children born and reared in two different fluoridated areas, one in which powdered milk suspended in tap water was commonly used (Narssaq, Greenland: 1.1 ppm fluoride in the water) and one in which cow's milk was provided (Vordingborg, Denmark: 1.4-1.6 ppm fluoride in the water). Dental fluorosis was recorded by Thylstrup and Fejerskov's classification. In both locations, the prevalence of dental fluorosis increased the later in life the tooth type was formed. The prevalence of dental fluorosis in the earliest formed teeth was higher in the area where powdered milk was suspended in fluoride-containing tap water than where pasteurized cow's milk was used. In the first permanent molars, the maxillary incisors, and the canines, the prevalence was rather similar in the two areas. In the latest formed teeth, the premolars, the level of fluorosis was higher in Vordingborg. The pattern of dental fluorosis suggests that when powdered milk was used frequently, the children were exposed to a higher fluoride intake earlier in life than were those consuming cow's milk during infancy and childhood.

Adolescent↗
PubMed1988

Maturation in developing permanent porcine enamel.

Mineral content per tissue volume was investigated in developing permanent porcine enamel and contrasted with weight-related data. Levels of mineralization were correlated directly with the histological appearance of the overlying enamel organ. Magnesium concentrations were measured at different stages of enamel development. Mineral levels rose from approximately 30% per volume of tissue during the secretory stage to approximately 60% in mature tissue. This is much lower than final mineral levels in enamel of other species. Enamel containing low mineral levels was adjacent to tall secretory ameloblasts which had reduced in height by approximately 50% at a point corresponding to the beginning of the maturation stage. Magnesium concentrations remained relatively constant throughout the secretory stage, at 0.2% Mg by weight. These rose by 3-4 times in the enamel of the maturation stage. The low levels of mineralization in the mature porcine enamel did not appear to be due to enamel pathology, and the possibility of porcine teeth erupting in an immature, partially porous condition is discussed.

Ameloblasts↗
PubMed1987

Scanning electron microscopy of early microbial colonization of human enamel and root surfaces in vivo.

This study describes the pattern of microbial colonization in six dental students, who carried test pieces of enamel and root surface in intraoral acrylic appliances for 4, 8, 12, 24, and 48 h, respectively. Oral hygiene was discontinued during the experimental periods. The results showed that oral microorganisms colonized enamel and root surfaces individually. The pattern of colonization mimicked the surface structure of the tooth; on enamel surfaces the first bacteria appeared in pits and surface irregularities followed by proliferation along the perikymata, while on root surfaces bacterial colonization was characterized by a haphazard distribution. Within the initial 24-h period root surfaces were more heavily colonized than were enamel surfaces. This pattern was characteristic irrespective of differences in the intra- and interindividual rates of bacterial coverage. It is concluded that early microbial colonization in vivo is determined by the surface structure of the tooth. Consequently, natural tooth surfaces should not be replaced by artificial surfaces in structural studies of microbial deposits in the oral cavity.

Adult↗
PubMed1987

Transmission electron microscopy of early microbial colonization of human enamel and root surfaces in vivo.

This study describes the early microbial colonization of teeth by the use of light- and transmission electron microscopy. Six dental students carried a total of 60 test pieces of unerupted enamel and root surface in intraoral acrylic appliances for 4, 8, 12, 24 and 48 h, during which periods oral hygiene was abandoned. Pronounced variations were recorded in structure and thickness of the pellicle across the individual surfaces of both dental tissues. Bacterial single-cell colonization increased the electron density of the adjoining pellicle. Micro-colonies of bacteria were observed in relation to enamel surface irregularities such as perikymata, while the distribution on root surfaces appeared incidental. Root surfaces were generally colonized by thicker deposits than homologous enamel surfaces although the structural composition of the microbiota was similar. Gram-positive bacteria with thick cell walls appeared in coccoid or rod-shaped configurations depending on the age of the bacterial deposit. These bacteria were further characterized by selective invasion between collagen fibers. After 48 h the complexity of the microbiota was increased by the establishment of new bacterial species in the superficial layer. It is concluded that the pattern and composition of the early microbiota on teeth is more complex and variable than hitherto assumed.

Bacteria↗
PubMed1987

Developmental stages in permanent porcine enamel.

Developing permanent teeth of different ages were obtained from Danish Landrace pigs. Visibly distinct zones on their enamel surfaces were shown to correspond to changes in chemical composition previously reported for other species. The time of appearance, rate of progress and duration of each stage was determined for each tooth type.

Animals↗
PubMed1986

Parathyroid glands, calcium, and vitamin D in experimental fluorosis in pigs.

The purpose of this study was to determine whether total serum calcium, parathyroid gland structure, and/or levels of parathyroid hormone, 1,25 and 24,25 DHCC, are altered in pigs with dental and skeletal fluorosis. Eight experimental animals receiving 2 mg F-/kg b.w. per day from age 8-14 months were compared with eight controls. Concentrations of plasma fluoride and total plasma calcium were assessed at intervals throughout the experiment and during a 48 hour period at day 110-111 of the experiment. At the same time, concentrations of immunoreactive parathyroid hormone were measured using a homologous labeled antibody for porcine hormone, and a radioimmunoassay was used to assess concentrations of 1,25 DHCC and 24,25 DHCC. Parathyroid tissue volumes were assessed at the end of the experiment by quantitative histology using volumetry and point counting. Plasma fluoride increased from 0.0007 +/- 0.0001 mmol/liter to 0.0127 +/- 0.002 mmol/liter in pigs receiving fluoride. In spite of this increase, total plasma calcium remained the same throughout the experiment. Volumes of parathyroid tissue, and levels of circulating parathyroid hormone 1,25 DHCC and 24,25 DHCC, were not significantly changed. It was therefore concluded that disturbance of calcium homeostasis is not an obligatory finding in dental and skeletal fluorosis and consequently does not play an essential role in the pathogenesis of these hard tissue lesions.

Animals↗
PubMed1986

Tooth loss as related to dental caries and periodontal breakdown in adult Tanzanians.

A total of 170 adults aged 30-69 yr from the Zanzibar and Pemba Islands (Tanzania) were examined for tooth loss, dental caries and loss of periodontal attachment. The cause of tooth loss was recorded from information given by the examinee to a Kiswahili-English interpreter. Dental caries were recorded according to the depth of the lesion, i.e. involving enamel, dentin or pulp, respectively. Loss of attachment was measured as the distance in mm from the CEJ to the bottom of the pocket. The most severely affected surface determined the state of the tooth. The mean number of teeth present ranged from 29.5 in the youngest to 23.9 in the oldest age group. The mean number of teeth missing due to dental caries ranged between 2.1 and 7.0 teeth, and exceeded by far tooth loss due to periodontal breakdown which was only observed in the two oldest age groups. In all age groups the molars were the teeth most frequently missing and also the teeth most frequently affected by dental caries. Although a substantial number of the teeth in the older age groups demonstrated an extensive loss of attachment only a few teeth, mainly mandibular incisors, were lost due to periodontal breakdown within the age range examined.

Adult↗
PubMed1986

Active root surface caries converted into inactive caries as a response to oral hygiene.

The clinical characteristics of 24 active root surface lesions on buccal surfaces were recorded through 18 months after implementation of meticulous toothbrushing with a fluoride toothpaste (F congruent to 0.1%). Within a period of 2-6 months all lesions had changed from soft, greasy and yellowish to leathery or hard, darkly discoloured tissue, indicating a gradual transition from active into inactive stages of caries. The observations stress the dynamic nature of the root caries process. It is concluded that when dealing with root surface caries it is essential to distinguish between active and inactive lesions and that classical operative treatment to a great extent can be avoided.

Adult↗