External influences on dental schools and their curricula. The influence of dental research on qualifications of clinical faculty staff.
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Curriculum↗
Biomedical subjects
O Fejerskov
Publications and source records attributed to O Fejerskov.
The effects of xylitol-containing chewing gums on dental plaque and acidogenic potential.
The aim of this study was to test the hypothesis that the chewing of xylitol- or xylitol/sorbitol-containing chewing gum reduces plaque formation and the acidogenic potential of dental plaque. Thirty healthy volunteers aged from 19 to 28 yrs were randomly allocated to one of three test groups, chewing either xylitol-, xylitol/sorbitol-, or sucrose-sweetened gums. A three-day plaque accumulation period of no oral hygiene was instituted prior to and at the termination of the chewing gum program, which lasted 33 days. Plaque quantity was assessed on the basis of protein content of individual plaque samples collected by a standardized technique. Acidogenic potential of individual baseline and test plaque samples was assessed by the quantity of various organic acids formed from D-(U-14C)glucose. Identification of extracellular and intracellular metabolites was performed by HPLC. Statistical evaluation of data was performed according to paired comparisons of individual baseline and post-chewing data. Plaque formation, acidogenic potential, and glycolytic profiles were similar at baseline and after the gum-chewing periods. Also, there was no intracellular accumulation of glycolytic metabolites within the plaque bacteria to indicate the inhibition of glycolysis. The study thus leads to the conclusion that, in young adults with low caries experience, exposure of the oral cavity to acceptable doses of xylitol or xylitol and sorbitol has no effect on the microbial deposits on the teeth.
Acetic Acid↗
Concepts of dental caries and their consequences for understanding the disease.
The way in which we conceptually consider dental caries determines our choice of preventive and treatment strategy. In this paper the definition of dental caries is discussed and the related problems concerning causality are addressed. Dental caries reflects symptoms of ongoing and past disease--not the disease itself. As such, it is important to record early stages of signs of the disease, i.e. non-cavitated stages of lesion development. The dynamic nature of the processes leading to net loss of mineral (hence a lesion) is emphasized, and appreciating that caries is ubiquitous in populations around the world and initiation and progression of lesions continues lifelong leads to the logical conclusion that we can control dental caries through a variety of measures--but not truly prevent the disease. We can prevent cavities by controlling the patho-physiological events which may result in a net loss of mineral. The relative role of dental plaque in caries control is discussed in relation to the role of the many determinants which influence the likelihood for lesion development. It is concluded that several paradigms about the nature of dental caries should be reconsidered to provide the most cost-effective dental services.
Cost-Benefit Analysis↗
Assessing the stage of caries lesion activity on the basis of clinical and microbiological examination.
The dynamic nature of caries lesion progression may require that classification of caries lesions makes distinctions in activity status. The aim of the present review was to compile and discuss the literature which pertains to clinical assessment of caries lesion activity, and to examine whether recent developments in microbiological research may justify the use of microbiological methods for evaluation of caries activity. Clinical observations suggest that caries lesion progression can be arrested at any stage of lesion development, provided that clinically plaque-free conditions are obtained. However, there is no universal level of oral hygiene to be recommended. The diagnoses "active" and "inactive/arrested" caries have been validated by a range of histological and chemical methods which have supported a separation into distinct clinical categories. Simple microbiological methods have so far not been useful in differentiating between active and inactive caries lesions. Very few studies have evaluated the inter- and intraexaminer reliability of caries diagnostic criteria based on assessment of the activity state of lesions, but recent data indicate that active and inactive caries lesions can be diagnosed with a high degree of reliability. A decision-making tree for dental caries is presented by means of which it is possible to associate the assessment of caries lesion activity with an appropriate treatment modality. It is concluded that research into better methods of assessing caries lesion activity clinically should be stimulated.
Decision Trees↗
Predictors of tooth loss over 10 years in adult and elderly Chinese.
This study describes the incidence of tooth loss over a 10-year period in a population of rural Chinese, initially aged between 20 and 80 years. Among the 587 persons who participated in a baseline examination in 1984, 440 persons were available for a follow-up study in 1994. A total of 31 persons, mainly aged 50+ years at baseline, had become completely edentulous. Between 45% and 96% of the persons lost at least one tooth, and the average number of teeth lost ranged between 1.0 and 7.2. The distribution of the number of teeth lost was skew, indicating that a minor group of subjects had a substantially higher risk of tooth loss than the majority. Logistic regression analysis identified six significant predictors of tooth loss among those who remained dentate: age, a high number of teeth with dentinal caries lesions, a high number of teeth with caries lesions of any type, presence of teeth with attachment loss > or = 7 mm, presence of mobile teeth, and a low percentage of sites with subgingival calculus deposits. At the subject level, caries variables and periodontal disease variables seemed equally important predictors of the incidence of tooth loss over 10 years, but at the tooth level caries was a predominant cause of tooth loss in all age groups.
Adult↗
Predictors of destructive periodontal disease incidence and progression in adult and elderly Chinese.
This study describes some predictors of new and progressing destructive periodontal disease over a 10-year period in rural Chinese. A total of 398 persons aged 20-80 years, who had participated in a baseline survey of tooth mortality, dental caries and periodontal conditions and were still dentate 10 years later, were reexamined for the same parameters as assessed at baseline. Three different threshold values were used to define new and progressing destructive periodontal disease. Irrespective of the threshold used, most persons experienced new disease. Progressing disease was very prevalent when a 2+ mm disease definition was used, but occurred less frequently at the higher threshold levels. The logistic regression models for 2+ and 3+ mm disease were essentially similar, and showed that women, persons with 104 sites or more, and persons with 0-5% sites with 4+ mm attachment levels had a lower risk of disease progression as well as of new disease than did men, persons with few sites and persons with 6% sites or more with attachment levels 4+ mm. The variables sex, number of sites present, percentage of sites with 4+ mm attachment levels, and presence of mobile teeth were predictive for new disease using a 4+ mm definition. Age, percentage of sites with 4+ mm attachment levels and percentage of sites with 4+ mm pockets were predictive for progressing disease using the 4+ mm disease definition.
Adult↗
Arrest of root surface caries in situ.
This study tests the hypothesis that daily oral hygiene combined with topical fluoride arrests active root-surface caries lesions without changing the mineral content of the lesions. Therefore, changes in mineral content and distribution were studied in root surfaces during caries lesion development and subsequent arrest of lesion progression in situ. In 18 subjects, lesions were developed during 3 months in sound root-surface specimens inserted into lower partial dentures. After 3 months, ground sections were prepared from each lesion prior to re-insertion of the specimens into the dentures. In addition, one sound root specimen was added per subject. During the following 3 months, half of the subjects cleaned both sound and carious specimens once a day with an 1100-ppm fluoride toothpaste, and the specimens were treated twice with 2% NaF for 2 min in situ. The other half of the subjects continued the experiment without cleaning. During the initial three-month period, all specimens developed subsurface lesions extending 187 to 583 microm into the dentin. Lesion depth increased somewhat in both experimental groups during the following 3 months (P > or = 0.1). There was a non-significant increase in mineral loss in the plaque-covered specimens (P = 0.08). However, the total mineral content of specimens subjected to plaque removal and topical fluoride did not change. This treatment resulted in an increased mineral content in the surface layer (P < 0.01) and formation of a zone of higher mineral content within the body of the lesion. The sound root surfaces which had been cleaned for a three-month period showed mineral uptake in the surface layer, occasionally associated with subsurface demineralization extending 20 to 70 microm into the tissue. The mineral loss of these specimens was significantly smaller than that of plaque-covered surfaces (P < 0.001). It is concluded that daily plaque removal and topical fluoride use influence the distribution of mineral in sound and carious root surfaces and may arrest lesion progression without affecting the total mineral content.
Aged↗
A 10-year study of the progression of destructive periodontal disease in adult and elderly Chinese.
This study describes the progression of destructive periodontal disease among Chinese aged 20 to 80 with limited access to dental health facilities and minimal traditions for oral hygiene procedures. These individuals were followed for 10 years to determine whether the rates for progression of periodontal disease were markedly different than for populations with more access to oral health care. At baseline, participants had been examined for tooth mobility, plaque, calculus, gingival conditions, attachment levels, and probing depths on 4 sites of each tooth present. These probing depth and attachment level recordings were repeated at follow-up, although third molars were excluded from examination. A total of 398 persons remained dentate at follow-up. The analysis demonstrated that virtually all subjects experienced > or = 2 mm attachment loss over the 10-year period, and frequently in a large proportion of the sites present. Attachment loss > or = 3 mm was also widespread, but the distribution of persons according to the extent of > or = 3 mm attachment loss was positively skewed in all age groups. Positive skewness was even more pronounced when attachment loss of > or = 4 mm was considered. Some types of teeth, such as mandibular incisors and maxillary molars, had higher progression rates than did, for example, maxillary incisors. The mean individual attachment loss rates did not differ significantly between age groups, and were remarkably similar to those reported for populations whose access to and tradition for oral health care is widespread.
Adult↗
Subgingival microbiota in adult Chinese: prevalence and relation to periodontal disease progression.
The "checkerboard" Dna-Dna hybridization technology was used to study the epidemiology of 18 microbial species associated with various states of periodontal health and disease, in a sample of 148 Chinese subjects never exposed to systematic dental therapeutic intervention, aged 30 to 39 and 50 to 59 years. Our aims were to: 1) describe the prevalence of these microorganisms; 2) correlate the microbiological and clinical profiles of the subjects; and 3) examine the association between the microbiological variables and the longitudinal changes of periodontal status that occurred over a preceding 10-year period. A maximum of 14 subgingival samples were obtained from each subject-1,864 in all. The frequency of occurrence of the 18 species examined was high in this Chinese population, on both the subject and the tooth site level. However, all species were not found equally capable of reaching high numbers in the subgingival samples and, as a rule, colonized heavily only limited proportions of tooth sites within each mouth. There was a profound increase of certain species such as Porphyromonas gingivalis, Treponema denticola, and Bacteroides forsythus in deep pockets or progressing sites. Multivariate techniques using the subgingival profile could effectively discriminate between deep/shallow pockets and progressing/ stable tooth sites. The microbiological variables showed an enhanced discriminating potential when classifications were performed on the individual subject level. Colonization by P. gingivalis, B. forsythus, Campylobacter rectus, and T. denticola at levels exceeding certain thresholds entailed a significantly increased probability (odds ratios > 4) for an individual subject to harbor deep pockets or progressing tooth sites.
Adult↗
Profiles of destructive periodontal disease in different populations.
In this study we evaluated the traditional view that the severity of periodontal disease varies between populations in that African and Asian populations are more severely affected than other populations. Our data on periodontal destruction in two random samples of a Kenyan and a Chinese adult population were recalculated to conform with the methods of examination and data presentation utilized in each of 6 other studies of attachment loss levels in different populations. The adult Kenyan and the adult Chinese group, who had very poor oral hygiene conditions and massive gingival inflammation, had attachment loss levels which were quite similar to those in a Japanese population (31), in a Norwegian population (27) and in a New Mexico group of adults (30). Attachment losses were similar in a population of young US adults (26) aged between 35 and 60 years relative to the corresponding Kenyan and Chinese groups while young US citizens had higher and elderly US citizens had lower mean attachment levels than either Kenyans and Chinese. Higher attachment loss levels beyond the age of 27 years were reported for a population of Sri Lankan Tamil tea workers (27) and across all ages in two South Pacific island populations (29). Overall, the analysis indicates that the periodontal attachment loss profiles may differ between populations, but that these differences do not conform with the traditional generalization that African and Asian populations suffer more severe periodontal breakdown than other populations.
Adolescent↗
Transmission electron microscopy of cementum crystals correlated with Ca and F distribution in normal and carious human root surfaces.
Root-surface caries, like enamel caries, develops as a subsurface type of mineral loss. Very little is known about the composition of the surface zone covering the body of the lesion, and the ultrastructure and composition of carious cementum are not known. The aim of this study was to correlate the ultrastructure and arrangement of the cementum crystals with the distribution of fluoride and calcium in root cementum from human teeth with sound, unexposed, or exposed root surfaces as well as in early stages of root-surface caries. Microradiographically, unexposed specimens showed a relatively homogeneous mineral distribution contrasting with the formation of an apparently highly mineralized surface layer in exposed and, in particular, in carious cementum. The electron-probe findings showed a substantial fluoride peak corresponding to the surface layers in carious tissues in particular, whereas the calcium profile in the surface did not reflect the apparent increase in mineralization. A substantial increase in size of the cementum crystals was found in specimens with formation of the fluoride-rich, well-mineralized surface zone. The crystal lattice intervals when observed along the (001) plane showed a hydroxyapatite spacing. The findings indicated that a significant crystal growth can be achieved in human cementum concomitant with fluoride accumulation.
Adult↗
Plaque pH and microflora of dental plaque on sound and carious root surfaces.
Given the hypothesis that root caries is the result of acid formation by acidogenic micro-organisms, the present study was performed to relate sucrose-induced pH response of dental plaque on root surfaces to the microbial composition of the overlying plaque. Seventeen caries-active elderly Chinese with poor oral hygiene and with both sound and carious root surfaces were examined. Plaque pH was measured before and up to one hour after a controlled sucrose mouthrinse. Plaque samples for microbiologic analyses were collected from 2 sound and 2 or 3 carious pH-measurement sites in each subject. The prevalence of the following micro-organisms was assessed as % of total viable counts on Brucella agar: Prevotella intermedia, Prevotella melaninogenica, Fusobacterium nucleatum, Campylobacter rectus, Capnocytophaga spp., Actinomyces viscosus, Actinomyces naeslundi, Streptococcus spp., S. sanguis, S. mitis, S. mutans, S. sobrinus, Lactobacillus spp., and Candida spp. There was no difference in plaque pH response on sound and carious root surfaces. The plaque pH response was more pronounced in the maxilla than in the mandible for both sound and carious sites. There was no difference in microbial composition of dental plaque on sound and carious root surfaces. The pH response to sucrose was the same regardless of the presence or absence of mutans streptococci. Our results thus do not readily support the traditional concept of caries formation.
Aged↗
Structural changes in fluorosed dental enamel of red deer (Cervus elaphus L.) from a region with severe environmental pollution by fluorides.
A macroscopic, microradiographic and scanning electron microscope study was performed on the structure of fluorosed dental enamel in red deer from a fluoride polluted region (North Bohemia, Czech Republic). As was revealed by analysis of mandibular bone fluoride content, the rate of skeletal fluoride accumulation in the fluorotic deer was about 6 times that in controls taken from a region not exposed to excessive fluoride deposition. In all fluorosed mandibles, the 1st molar was consistently less fluorotic than the other permanent teeth. This was related to the fact that crown formation in the M1 takes place prenatally and during the lactation period. Fluorosed teeth exhibited opaque and posteruptively stained enamel, reduction or loss of enamel ridges, moderately to grossly increased wear and, in more severe cases, also enamel surface lesions of partly posteruptive, partly developmental origin. Microradiographically, fluorosed enamel was characterised by subsurface hypomineralisation, interpreted as a result of fluoride interference with the process of enamel maturation. In addition, an accentuation of the incremental pattern due to the occurrence of alternating bands with highly varying mineral content was observed in severely fluorosed teeth, denoting fluoride disturbance during the secretory stage of amelogenesis. A corresponding enhancement of the incremental pattern was also seen in the dentine. The enamel along the more pronounced hypoplasias consisted of stacked, thin layers of crystals arranged in parallel, indicating that the ameloblasts in these locations had lost the distal (prism-forming) portions of their Tomes processes. The findings of the present study indicate that red deer are highly sensitive bioindicators of environmental pollution by fluorides.
Animals↗
The effects of a mouthrinse containing sodium benzoate and alcohol on the quantity and metabolism of dental plaque.
The aim of this study was to investigate the efficacy of a pre-brushing rinse containing sodium benzoate and alcohol, on 2 week old dental plaque. In a double-blind, placebo-controlled crossover study 20 individuals abstained from oral hygiene for periods of 2 weeks. Ten individuals were then assigned to rinse once for 30 seconds with either the test mouthrinse or a placebo mouthrinse. Following this, all individuals had their teeth cleaned and maintained proper oral hygiene for four weeks before the experiment was repeated. This time, the control individuals were assigned to the test rinse and vice versa. Using the Plaque Index on three buccal sites on all teeth, plaque was recorded before and after rinsing, as well as following a subsequent toothbrushing. For metabolic studies plaque from the lingual surfaces on the teeth in one quadrant in the upper and the lower jaw was sampled before rinsing and from the two remaining quadrants following the rinse, and analysed. There was no difference in Plaque Index between the two experimental periods. An oral rinse with the test mouthrinse had no effect on the amount of plaque, nor did it enhance the subsequent plaque removal after brushing. The independent biochemical analysis showed a significant effect of rinsing on the glycolytic potential, but with no effect on the glycolytic profile, which was similar for test and control plaque samples. Thus, a single oral rinse with a mouthrinse containing sodium benzoate and alcohol does not affect removal of plaque nor does it seems to influence the glycolytic potential of the plaque.
Acids↗
Relationship between CPITN and periodontal attachment loss findings in an adult population.
This study investigates the relationship between CPITN findings and the prevalence and severity of periodontal attachment loss in a rural Kenyan population comprising 1131 persons aged 15-65 years. All persons were examined for calculus, gingival bleeding, pocket depths and attachment loss levels on 4 sites of each tooth present. Recordings of bleeding, calculus and pocket depths were used to compute CPITN scores based on the 10 index teeth originally proposed, and these CPITN scores were subsequently related to the attachment loss findings derived from the full-mouth assessment. In most cases, persons with a CPITN score < or = 1 did not have attachment loss > or = 4 mm. However, among 40+ year-old persons with CPITN score 2 over 90% had attachment loss > or = 4 mm and over 50% of the 50+ year-olds with CPITN score 3 had attachment loss > or = 6 mm. Less than 20% of the 15-29 year-olds with CPITN score 3 had attachment loss > or = 6 mm, and usually the attachment loss levels ranged between 0 and 3 mm. Beyond the age of 35 years over 10% of the sextants with CPITN score 0 had attachment loss > or = 4 mm. Below the age of 35 years more than one third of all sextants with CPITN score 3 had attachment loss levels < or = 3 mm. Thus, the CPITN findings overestimate both prevalence and severity of periodontal attachment loss among the younger age groups and underestimate these parameters among elderly subject.
Adolescent↗
Periodontopathogens in elderly Chinese with different periodontal disease experience.
If an etiological relationship exists between destructive periodontal disease and putative periodontopathogens, they would be expected to have a very low prevalence in periodontally healthy elderly persons. To test this hypothesis, 2 subgroups of elderly, rural Chinese (a periodontally "best" and a "worst" group, each comprising 15 persons) were identified in 1990 from a cohort aged 55-69 years, examined in 1984. Assessment of changes in periodontal status over the 6-year period were possible by comparing detailed clinical recordings performed by the same examinator. Subgingival microbial samples were taken at the mesial aspects of an upper central incisor and a lower canine and examined for the presence of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia group, Prevotella melaninogenica group, Capnocytophaga, Selenomonas, Campylobacter rectus as well as predominant Streptococcus and Actinomyces species. During the 6 years prior to microbiological sampling, persons in the "best" group had lost an average of 1.21 +/- 0.48 mm attachment, while persons in the "worst" group had lost an average of 1.60 +/- 0.94 mm. The latter group had lost 53.3 teeth, predominantly for periodontal reasons, in contrast to 1.8 teeth lost in the "best" group. "Best" persons did not differ from "worst" persons with respect to the occurrence of the putative periopathogens, total viable count, and total streptococcal and Actinomyces recovery. Similarly, sites which had experienced an attachment loss > or = 2 mm during the 6-year period did not differ microbiologically from sites with less attachment loss. It is concluded that subgingival microbial characterization does not allow for a distinction between elderly individuals with markedly different periodontal disease experiences.
Actinomyces↗
Strategies in the design of preventive programs.
Dental caries is mostly recorded at the cavity level only. A reduced mean number of cavities in new age cohorts is often thought of as a result of prevention of the disease, dental caries. However, what is measured is rather our success in controlling the disease in such a way that prevalence of its more severe manifestations (cavities) can be reduced in children. Caries lesions and periodontal breakdown are cumulative with age and progress steadily in all populations. Thus, caries is the predominant reason for tooth loss in almost all age groups. The low prevalence and skewed distribution of dental caries make several fluoride programs less (if at all) cost-effective. Rather than considering a "whole population strategy" as opposed to a "high-risk strategy", it is argued that they should go hand in hand. However, the high-risk strategy may appear to have an unfavorable ratio of benefits to costs. So far the available literature shows no evidence that we have tests which, with sufficient predictive power, can identify groups or individuals of "high risk". It is therefore concluded that a population strategy should be maintained and further developed with emphasis on oral hygiene, because it influences norms and behavior. More knowledge about the pathogenesis of oral disease is needed before we can develop truly cost-effective strategies for the prevention of caries and periodontal breakdown.
Adolescent↗
Approximal plaque pH following topical applications of standard buffers in vivo.
In this study, the null hypothesis was tested that topical application of standard buffer solutions, pH 7.00 and pH 4.01, to 4-day-old plaque deposits accumulated in situ causes the plaque to attain the pH values of the buffer solutions applied. Following a 4-day abstention from all oral hygiene procedures, the plaque pH of four interdental sites in each of 5 volunteers was measured at resting state and following topical applications of buffers pH 7 and pH 4. Later the same day plaque pH was measured following rinses with the buffers. Topical application of buffer pH 7 caused a plaque pH increased from a mean value of 6.40 to 6.59 within 30 s, while buffer pH 4 caused plaque pH to drop to a mean value of 5.11. Rinsing with buffers caused plaque pH to increase to 6.50 (buffer pH 7) and to drop to 4.92 (buffer pH 4). Statistical analysis of the results led to rejection of the null hypothesis. The results thus indicated that the validity of the in situ approach of calibration of plaque-covered indwelling electrodes may be questioned.
Administration, Topical↗