Biomedical subjects

O Fejerskov

Publications and source records attributed to O Fejerskov.

At least 91 records · Page 5Linked to original sources

PubMed1989

Transition dynamics in experimental gingivitis in humans.

This study was conducted in order to investigate the dynamics of the gingival inflammatory status during periods of plaque accumulation and thorough oral hygiene. After a period of prophylaxis, 42 volunteers were asked to abstain from all oral hygiene measures for 2 weeks, whereafter oral hygiene was reinstituted. In the absence of oral hygiene, plaque was found at virtually all sites after 7 days and the number of sites with gingivitis increased simultaneously. A reduction in gingival inflammation occurred subsequent to plaque removal. During phases of both plaque accumulation and thorough oral hygiene, sites were found to convert from non-inflamed to inflamed status concurrently, as in the reverse direction. No association between plaque and gingivitis was revealed. The gingival status of a single site was a poor predictor of its status on the subsequent occasion. The proportion of inflamed sites converting to non-inflamed status was greater than the proportion of non-inflamed sites converting to inflamed status at any time. The estimated incidence rate remained fairly constant during both the plaque accumulation phase and the oral hygiene phase, whereas the estimated recovery rate was considerable lower during the plaque accumulation phase compared to oral hygiene phase. The clinical appearance is the outcome of the dynamics between these rates. The steady-state prevalences derived from the estimated "incidence" and "recovery" rates were quite similar to the actual findings after 14 d of plaque accumulation and the subsequent 10 d of thorough oral hygiene.

Adult↗

PubMed1989

Pattern of dental caries in an adult rural population.

A study was conducted amongst 1,131 randomly selected persons aged 15-65 years in a rural area of Kenya, having minimal access to dental care. A relatively low prevalence of frank cavitation was found in the 15- to 24-year-old cohort, but in the older age groups over 80% were so affected. Caries in the youngest cohort was characterized by a predominance of enamel lesions. At the age of 25-34 years, however, involvement of pulpal tissues and loss of teeth due to caries was more common, and this age group exhibited the largest number of dentinal lesions. The 35- to 44-year-old cohort exhibited fewer enamel and dentinal lesions, but more pulpally involved lesions and more extracted teeth. In the group aged 45-54 years, enamel and dentinal lesions were less common, and at the age of 55-65 years, such lesions were less common in comparison to their occurrence in younger cohorts. The 55- to 65-year cohort could generally be characterized as having larger numbers of root surface lesions, lesions involving the pulp, and extracted teeth. Root surface lesions were principally associated with age over 35 years. In all age groups caries exhibited a skewed distribution, most of the lesions occurring in a minority of individuals. This study demonstrates that caries activity continues throughout life and is not a phenomenon confined to any one period of life.

Adolescent↗

PubMed1989

Structure of dental plaque and the plaque-enamel interface in human experimental caries.

This study describes the ultrastructure of dental plaque and the plaque-enamel interface after 2 and 3 weeks' exposure to a cariogenic challenge. Five dental students carried a total of 25 specimens of smooth surface enamel in intraoral acrylic appliances. During the initial 3 days the volunteers refrained from oral hygiene and performed nine daily mouthrinses with 10% (w/v) solutions of sucrose. After the 3rd day the volunteers cleaned their natural teeth, whereas the experimental sites were left undisturbed except for nine daily extraoral 5-min immersions in 5% (w/v) solutions of sucrose. Clinically, three patterns of colonization were observed after 3 days. At the histological level the experimental bacterial deposits also exhibited three distinctly different structural patterns after 2 and 3 weeks. Individual patterns consistently differed with regard to the microbial composition, the structural organization of the deposits, and the presence or absence of crystal-like material. However, in all individuals a layer of densely packed gram-positive bacteria resembling Actinomyces was consistently present close to the enamel surface. In 1 individual the microbial deposits were dominated by large bacteria, the ultrastructure of which conformed to the description of Stomatococcus mucilaginosus. These findings may partly explain pronounced individual variations in the rate of caries lesion development and progression in vivo.

Bacteria↗

PubMed1989

Microradiography of experimental root surface caries in man.

The aim of this study was to describe the pattern and rate of mineral loss during experimental root surface caries in situ without giving frequent sucrose rinses as a supplementary cariogenic challenge. Six elderly persons carried at total of 18 specimens of unerupted human root surface in recessions of lower partial dentures for 1, 2 and 3 months. Another six root surfaces served as controls. No cleaning of the specimens was allowed during the experimental period whereas the natural dentition was cleaned with a nonfluoride toothpaste. All the specimens, as observed by quantitative microradiography, exhibited subsurface caries lesions. Despite variation between individuals the depth of subsurface demineralization increased linearly with time, the average depth of the lesions being 240 microns after 1 month and 630 microns after 3 months. Delta MC, calculated as the difference in total mineral content between control and test specimens throughout the lesions, increased linearly with time from 2,000 to 8,400 vol% microns after 1 and 3 months, respectively. Preparation for microradiography induced a certain shrinkage of the lesions which resulted in an underestimation of the actual loss of mineral. It is concluded that this experimental model is suitable for studying the etiology and prevention of root surface caries provided the interindividual variation is taken into account.

Aged↗

PubMed1989

Ultrastructural changes in Streptococcus sobrinus induced by xylitol, NaF and ZnCl2.

The effect of xylitol, NaF, or ZnCl2 on the ultrastructure of Streptococcus sobrinus OMZ 176 was studied. The bacteria were grown statically in air for 8 h in brain-heart infusion broth supplemented with 33 mM Xylitol, 2.5 mM NaF, 0.5 mM ZnCl2, separately or in combination. The bacteria were washed briefly and prepared for scanning and transmission electron microscopy. All three agents and their combinations induced distinct ultrastructural alterations. The alterations were related to various aspects of cell morphology and varied in nature and extent among the agents. The most pronounced ultrastructural alterations were seen in bacteria grown in the presence of zinc ions. At the concentrations used, fluoride appeared to induce the least effect.

Chlorides↗

PubMed1989

Associations between salivary levels of Streptococcus mutans, Streptococcus sobrinus, lactobacilli, and caries experience in Kenyan adolescents.

Salivary levels of mutans streptococci (S. mutans and S. sobrinus) and lactobacilli were determined in a random sample of rural Kenyans between 15 and 19 years of age (n = 149). It is possible for the natural history of dental caries in this population to be studied since it is characterized by a limited access to conventional dental treatment. Using a short set of biochemical tests, we identified from seven to ten presumptive mutans streptococcus colonies--cultured from the saliva of each individual--to differentiate between S. mutans and S. sobrinus. No colonies resembling S. rattus (S. mutans serotype b) were isolated. Lactobacilli were identified as Gram-positive, catalase-negative rods. The mean D1-4MFS and D3-4MFS were 7.03 +/- 6.43 and 1.46 +/- 3.44, respectively. The mean mutans streptococcus and lactobacillus levels were 8.7 x 10(4) and 6.7 x 10(4), respectively. The salivary mutans streptococcus and lactobacillus levels were significantly correlated (p less than 0.01). Of the subjects, 64% harbored only S. mutans, 4% only S. sobrinus, 30% both species, and 2% neither. Lactobacilli were ubiquitous. The caries experience of the group was significantly (p less than 0.001) correlated with both the total salivary level of mutans streptococci and the salivary S. mutans levels, but not with the salivary S. sobrinus level.

Adolescent↗

PubMed1989

Dental caries in adult and elderly Chinese.

This paper reports on a study of dental caries conducted among 1744 urban and rural Chinese (from 20 to 80 years old), who were selected by means of a systematic stratified sampling procedure. The prevalence of one or more decayed or filled teeth ranged from 48 to 90% in urban residents, and from 51 to 97% in rural residents, depending on age. The mean number of decayed or filled teeth ranged from 1.2 (+/- 1.9) among 20-29-year-olds, to 6.2 (+/- 5.5) among 70+-year-olds, and was highest among rural residents. Among 20-29-year-olds, the main components of the DFT were enamel lesions and fillings. Among 30-49-year-olds, the DFT consisted mainly of enamel lesions and filled teeth, as well as teeth with lesions involving the pulpal tissues. In subjects over the age of 50 years, lesions involving pulpal tissues were the predominant type, followed by root-surface lesions. In subjects below the age of 50 years, most of the caries experience derived from coronal surfaces, particularly occlusal surfaces. Root-surface caries was predominantly a feature of persons aged 50 years and above. Despite a large number of surfaces being at risk of root-surface caries, less than 10% of the surfaces were so affected. Although cross-sectional in nature, these data indicate that when the oral hygiene standards are poor, caries lesions continue to develop and progress throughout life. With age, dental caries becomes a substantial oral health problem in this population of adult and elderly Chinese, despite the availability of some dental services.

Adult↗

PubMed1989

Enamel fluoride in relation to severity of human dental fluorosis.

The aim of this study was to test whether the concentrations of fluoride in fluorotic human enamel are related to the degree of severity of dental fluorosis classified according to the index described by Thylstrup and Fejerskov. Teeth representing the entire spectrum of human dental fluorosis were analyzed. Fluoride concentrations were determined by serial acid-etching from surface to interior of blocks of enamel cut from each tooth. Fluoride was measured by ion electrode and calcium by atomic absorption spectrophotometry. The results showed that the pattern of distribution of fluorotic enamel is similar to that described for normal enamel. Increasing severity of fluorotic lesions was associated with increasing concentrations of fluoride throughout the enamel. It is concluded that although further studies are required to establish the relative contribution of fluoride which may be taken up posteruptively by fluorotic enamel, the findings support the hypothesis that the TF index reflects increasing exposure to fluoride during tooth development.

Chi-Square Distribution↗

PubMed1989

Ultrastructure and composition of enamel in human dental fluorosis.

Materials used in this work were 13 permanent molars exhibiting dental fluorosis (between 5 and 9 on the Thylstrup-Fejerskov scale, 1978) obtained from adults (aged 20-40 years) living in regions with 3.5 ppm fluoride in the water supplies. Small but deep occlusal caries lesions necessitated extraction. Light and polarized microscopic, microradiographic, electron microscopic, and electron-probe- and ion-micro-analytical studies were made. Enamel surfaces were generally cloudy to opaque, with several pits or defects of various sizes and degrees of brown-staining. An extensively hypomineralized area extended from the inner enamel to the surface layer, which was mineralized to a high degree. The hypomineralized area contained sparsely arranged, flattened, hexagonal crystals with either perforated centers or defects extending from the perimeter and indicating either no or low fluoride content. The highly mineralized surface layer, however, was composed of many large, flattened, hexagonal crystals and extremely small, irregularly shaped crystals. Both types were free of central perforations and defects. A high fluoride concentration was determined in the highly mineralized surface layer. These findings suggest that the hypomineralized area undergoes caries-like changes in terms of crystal dissolution and that the highly mineralized surface layer contains hydroxyapatite and fluoridated-hydroxyapatite, or fluorapatite, or both.

Adult↗

PubMed1989

Chewing sticks, toothpaste, and plaque removal.

The aim of the present study was to assess the efficacy of brushing with chewing sticks in removing plaque and to evaluate whether toothpaste has any additional effect on the removal of established dental plaque. Kenyan schoolchildren had their plaque deposits disclosed by means of disclosing tablets and subsequently recorded on four buccal sites of all permanent teeth. The children were then allocated to two groups in a crossover design; in one group the children brushed with chewing sticks and toothpaste; the other group brushed with chewing sticks only. Substantial amounts of plaque were recorded at base line in most children. Brushing with a chewing stick for 5 min resulted in a net reduction of the proportion of plaque deposit sites per child. Toothpaste resulted in no additional effect.

Adolescent↗

PubMed1989

High resolution electron microscopy of enamel crystals in cases of human dental fluorosis.

Surface enamel from human subjects with dental fluorosis was studied by means of high-resolution transmission electron microscopy. Immediately below the relatively highly mineralized outermost surface enamel layer was an extensive hypomineralized area. The highly mineralized layer was composed of many large elongated hexagonal crystals and extremely small hexagonal crystals. Frequently the small crystals were attached to the periphery of the large crystals. In the hypomineralized area, large crystals were sparsely arranged; and a few small crystals were seen. Some large crystals showed either perforated centers or defects on their peripheries. These findings suggest that the hypomineralized area undergoes caries-like changes in terms of crystal dissolution and that the highly mineralized surface layer is either formed or modified by remineralization.

Adult↗

PubMed1989

Fluctuation of fluoride concentrations in drinking waters: a collaborative study.

The aim of this study was to describe the variations with time in the concentrations of fluoride in drinking water sources in Greenland, Kenya, Greece, Denmark and Ireland. Water samples were collected monthly and shipped to laboratories in Aarhus for electrometric analyses. In Narssaq, Greenland the fluoride concentration of a single piped water supply ranged from 0.3 to 2.8 ppm, the variations being related to climate, precipitation and temperature over the year. Water from the Athi River, Kenya had a fluoride content ranging from 0.3 to 1.2 ppm, the higher concentrations being associated with the dry seasons. The fluoride concentration in piped water from mountain rivers in Mourjes, Greece, ranged over the year between 1.3 to 2.0 ppm, the changes being apparently unrelated to rainfall. Marked variations in fluoride concentrations from 0.5 to over 3.5 ppm were observed in water from artesian wells in Assiros, Greece. In drinking waters from boreholes in Boennerup Strand, Denmark, fluoride concentrations ranged with time from 1.4 to 2.4 ppm, the variations being unrelated to climate or precipitation, while little variation in fluoride concentrations was found in water from boreholes in either Roedvig or Egens, Denmark. Water obtained from two sources of artificially fluoridated water supplies from Ireland showed considerable variations with time, although pooled samples indicated relatively constant levels over the year. The study indicates that the results of single fluoride ion measurement from any given source should not be taken as being a reliable indicator of fluoride exposure from drinking water.(ABSTRACT TRUNCATED AT 250 WORDS)

Denmark↗

PubMed1988

Periodontal diseases in adult Kenyans.

This study comprised 1131 persons who constitute a stratified random sample of the entire population aged 15-65 years in Machakos District, Kenya. Each person was examined for tooth mobility, plaque, calculus, gingival bleeding, loss of attachment and pocket depth on the mesial, buccal, distal and lingual surface of each tooth. The oral hygiene was poor with plaque on 75-95% and calculus on 10-85% of the surfaces depending on age. Irrespective of age, pockets greater than or equal to 4 mm was seen on less than 20% of the surfaces, whereas 10-85% of the surfaces had loss of attachment greater than or equal to 1 mm. The proportion of surfaces per individual with loss of attachment greater than or equal to 4 mm or greater than or equal to 7 mm, and pocket depths greater than or equal to 4 mm or greater than or equal to 7 mm, respectively, showed a pronounced skewed distribution, indicating that in each age group, a subfraction of individuals is responsible for a substantial proportion of the total periodontal breakdown. The individual teeth within the dentition also showed a marked variation in the severity of periodontal breakdown. Our findings provide additional evidence that destructive periodontal disease should not be perceived as an inevitable consequence of gingivitis which ultimately leads to considerable tooth loss. A more specific characterization of the features of periodontal breakdown in those individuals who seem particularly susceptible is therefore warranted.

Adolescent↗

PubMed1988

Tooth mortality and periodontal conditions in 60-80-year-old Chinese.

The study comprised 544 persons aged 60 yr or more from two urban Residential Areas and one rural village (including a nursing home) of Beijing area. Overall, the sample accounted for 81% of the total population of elderly aged 60 yr or more in the village/areas so defined. Each person was examined for dental status, plaque, calculus, gingivitis, loss of attachment, pocket depth and tooth mobility. Edentulousness was seen in 0-29% of the persons examined, depending on age and sex. The mean number of teeth present ranged from 6.9 to 23.9, depending on age and sex, and area. The oral hygiene was poor; approximately 50% of all surfaces had immediately visible plaque deposits and calculus. About 50% of the surfaces had a loss of attachment greater than or equal to 4 mm, while less than 15% presented pockets greater than or equal to 4 mm. More than 50% of the individuals had loss of attachment greater than or equal to 4 mm on more than 40% of their surfaces. The proportion of surfaces per person with loss of attachment greater than or equal to 7 mm; and pockets greater than or equal to 4 mm, respectively, showed a pronounced skewed distribution. These findings indicate that a subfraction of individuals is responsible for a substantial proportion of the severe periodontal breakdown leading to loss of teeth. This, in turn, raises important questions as to the most appropriate strategies for the prevention and control of periodontal diseases for the Chinese population.

Aged↗

PubMed1988

Organic structures of developmental origin in human surface enamel.

The aim of this study was to examine the distribution of organic material in mature enamel surfaces immediately prior to eruption. Thirty-six samples of buccal or lingual enamel from unerupted third molars were prepared for transmission electron microscopy by a method involving demineralization of the enamel after embedding in Epon. The results showed that at time of eruption human surface enamel is a highly porous structure containing large amounts of developmental protein which appear as a variety of triangular, funnel-shaped, or invaginated configurations extending into the enamel. The implications of this finding may be of importance to the understanding of early caries lesion formation in the enamel since organic structures may modify the diffusion of ions in and out of the tissue.

Crystallography↗

PubMed1988

Caries experience in urban Tanzanian children 1973-84.

In 1973 and 1984 the caries status of 624 and 394 children, respectively, was recorded in an urban area of northern Tanzania where the water fluoride content was 2.0-3.5 ppm. Although slightly different scoring criteria were used, the data showed very low levels of caries, and little evidence of increases in caries experience over the 10-yr period. The distribution of caries lesions was markedly skewed, such that a minority of individuals account for most of the caries. The levels of caries were low by international standards and equivalent to those found in children from low fluoride areas of Tanzania.

Adolescent↗

PubMed1988

Mineral and protein concentrations in enamel of the developing permanent porcine dentition.

Calcium, phosphorus and protein analyses have been performed on developing permanent enamel from the mandibular dentition of the domestic pig. The pattern of mineralization and protein loss was similar from tooth to tooth and similar to teeth from other species. Comparison of different teeth at the same developmental stages (secretion--stage 1, transition--stage 2 and maturation - stage 3) revealed remarkably similar concentrations of calcium, phosphorus, and protein regardless of tooth type. These data were similar to those from other deciduous dentitions, except that maturing/mature tissue in the pig seemed less well mineralized.

Age Factors↗

PubMed1988

Tooth mortality in an adult rural population in Kenya.

This paper reports on the pattern of tooth loss in a random sample of 1131 adults aged from 15 to 65 years in a rural area of Kenya in which access to formal dental care is minimal. We found that the majority of the population retained most of their dentition in a functional state even up to the age of 65 years: In all age groups, more than 50% had at least 26 teeth present, and more than 90% had at least 16 teeth present. The prevalence of edentulousness was less than 0.3%. The principal cause of tooth loss in all age groups was caries, and this was true for all tooth-types except incisors, for which periodontal disease was the main cause of tooth loss. The cultural practice of removing lower central incisors was observed only in those over 40 years of age. More teeth were lost due to caries among women than among men, while the reverse was true for teeth lost due to periodontal diseases. In view of the fact that most people retain most of their teeth throughout life, it is suggested that the most appropriate strategies for dental health care in this population should be those promoting self care, rather than the introduction of a formal treatment-oriented approach provided by dentists.

Adolescent↗