An Evaluation of the Role and Clinical Contribution of New Cross Dental Therapists

The first dental therapists (previously called dental auxiliaries), started their training in 1960 and, by the end of 1976, 792 women had qualified after a two-year course. In the present study the role of all dental therapists was investigated by means of a postal survey. The clinical contribution made by these ancillaries was assessed by means of a retrospective analysis of clinic day sheets recorded by 55 dental therapists employed in the community dental services. It was found that dental therapists, in terms of their working pattern and family profile, are typical of women of their age and level of qualification in Britain. The return to work by therapists, after a break from practice because of family commitments, will depend mainly on the availability of posts, particularly part-time posts. Dental therapists provide treatment predominantly for younger children. Compared with previous studies, a noticeable increase in the clinical preventive care provided by therapists was observed.

Improving the forecast for biodiversity under climate change

New biological models are incorporating the realistic processes underlying biological responses to climate change and other human-caused disturbances. However, these more realistic models require detailed information, which is lacking for most species on Earth. Current monitoring efforts mainly document changes in biodiversity, rather than collecting the mechanistic data needed to predict future changes. We describe and prioritize the biological information needed to inform more realistic projections of species' responses to climate change. We also highlight how trait-based approaches and adaptive modeling can leverage sparse data to make broader predictions. We outline a global effort to collect the data necessary to better understand, anticipate, and reduce the damaging effects of climate change on biodiversity.

What limits the evolutionary emergence of pathogens?

The ability of a pathogen to cause an epidemic when introduced in a new host population often relies on its ability to adapt to this new environment. Here, we give a brief overview of recent theoretical and empirical studies of such evolutionary emergence of pathogens. We discuss the effects of several ecological and genetic factors that may affect the likelihood of emergence: migration, life history of the infectious agent, host heterogeneity, and the rate and effects of mutations. We contrast different modelling approaches and indicate how details in the way we model each step of a life cycle can have important consequences on the predicted probability of evolutionary emergence. These different theoretical perspectives yield important insights into optimal surveillance and intervention strategies, which should aim for a reduction in the emergence (and re-emergence) of infectious diseases.

Resource competition and within-host disease dynamics

The host organism is a complex mosaic of cell populations that requires adequate supplies of nutrients for maintenance, growth and proliferation. Because many nutrient requirements may be shared by host cells, pathogens and indigenous microflora, all these cells may potentially compete for growth-limiting resources. Ecological theory can explain some of the dynamics commonly seen in host-pathogen interactions; and mechanistic resource-consumer theory provides an instructive framework for viewing the disease process.

Diverse and contrasting effects of habitat fragmentation

Different components of an ecosystem can respond in very different ways to habitat fragmentation. An archipelago of patches, representing different levels of fragmentation, was arrayed within a successional field and studied over a period of 6 years. Ecosystem processes (soil mineralization and plant succession) did not vary with the degree of subdivision, nor did most measures of plant and animal community diversity. However, fragmentation affected vertebrate population dynamics and distributional patterns as well as the population persistence of clonal plant species. The results highlight the dangers of relying on broad community measures in lieu of detailed population analyses in studies of fragmented habitats.

Allee effects, invasion pinning, and species' borders

All species' ranges are the result of successful past invasions. Thus, models of species' invasions and their failure can provide insight into the formation of a species' geographic range. Here, we study the properties of invasion models when a species cannot persist below a critical population density known as an "Allee threshold." In both spatially continuous reaction-diffusion models and spatially discrete coupled ordinary-differential-equation models, the Allee effect can cause an invasion to fail. In patchy landscapes (with dynamics described by the spatially discrete model), range limits caused by propagation failure (pinning) are stable over a wide range of parameters, whereas, in an uninterrupted habitat (with dynamics described by a spatially continuous model), the zero velocity solution is structurally unstable and thus unlikely to persist in nature. We derive conditions under which invasion waves are pinned in the discrete space model and discuss their implications for spatially complex dynamics, including critical phenomena, in ecological landscapes. Our results suggest caution when interpreting abrupt range limits as stemming either from competition between species or a hard environmental limit that cannot be crossed: under a wide range of plausible ecological conditions, species' ranges may be limited by an Allee effect. Several example systems appear to fit our general model.

Effects of species diversity on disease risk

The transmission of infectious diseases is an inherently ecological process involving interactions among at least two, and often many, species. Not surprisingly, then, the species diversity of ecological communities can potentially affect the prevalence of infectious diseases. Although a number of studies have now identified effects of diversity on disease prevalence, the mechanisms underlying these effects remain unclear in many cases. Starting with simple epidemiological models, we describe a suite of mechanisms through which diversity could increase or decrease disease risk, and illustrate the potential applicability of these mechanisms for both vector-borne and non-vector-borne diseases, and for both specialist and generalist pathogens. We review examples of how these mechanisms may operate in specific disease systems. Because the effects of diversity on multi-host disease systems have been the subject of much recent research and controversy, we describe several recent efforts to delineate under what general conditions host diversity should increase or decrease disease prevalence, and illustrate these with examples. Both models and literature reviews suggest that high host diversity is more likely to decrease than increase disease risk. Reduced disease risk with increasing host diversity is especially likely when pathogen transmission is frequency-dependent, and when pathogen transmission is greater within species than between species, particularly when the most competent hosts are also relatively abundant and widespread. We conclude by identifying focal areas for future research, including (1) describing patterns of change in disease risk with changing diversity; (2) identifying the mechanisms responsible for observed changes in risk; (3) clarifying additional mechanisms in a wider range of epidemiological models; and (4) experimentally manipulating disease systems to assess the impact of proposed mechanisms.

The prevalence of caries and of tooth tissue loss in a group of children living in a social welfare institute in Jeddah, Saudi Arabia

AIM

To measure the prevalence of caries, rampant caries and erosion in a group of 4-5-year-old children living in an institution in the city of Jeddah in the West Province of Saudi Arabia.

DESIGN

Descriptive, cross sectional.

SAMPLE AND METHODS

A total of 80 children (51 boys, 29 girls) living in the Institute were examined visually for caries using BASCD criteria. Erosion of palatal and buccal surfaces of maxillary incisors was scored: 0 (no erosion), 1 (erosion into enamel), 2 (erosion into dentine) and 3 (erosion involving the pulp).

RESULTS

Twenty-four of the Children (30 per cent) had caries and two had rampant caries. Mean dmft was 0.95 (+/- 2.03) and mean dmfs was 3.2 (+/- 6.51). These values are lower than other estimates for children of this age in Saudi Arabia. Ten children (12.5 per cent) had erosion affecting buccal or palatal surfaces of their maxillary incisor teeth. In seven, erosion was confined to enamel but in three it extended into dentine.

CONCLUSION

The lower caries levels seen in this group of children may be at least partly attributable to the effectiveness of strict dietary control and regular oral hygiene measures.

Oral health, sociodemographic factors, dietary and oral hygiene practices in Jordanian children

OBJECTIVES

To investigate the association between oral health, in terms of dental caries and gingivitis, and sociodemographic factors, dental plaque, oral hygiene behaviours, infant feeding and dietary practices in 4-5-year-old Jordanian children.

METHODS

Two-stage random sampling procedure was used to select children enrolled in kindergartens in Amman, Jordan. Clinical examinations were carried out by one examiner. Mothers completed questionnaires relating to sociodemographic factors, oral hygiene behaviours, infant feeding and dietary practices of the children.

RESULTS

About 67% of the children had caries, 31% had dmft greater than 4 and 66% had gingivitis. Of the children who had been wholly breast-fed, 86% had been fed on demand. Mothers of children attending kindergartens with the lowest tuition fees were more likely to have breast-fed their children on demand and for more than 18 months (prolonged breast feeding) compared to those attending kindergartens with higher fees. Savory snacks were consumed by 82%, confectionery by 76% and teas with sugar by 42% of the children. Multivariate analysis showed age, dental plaque, sleeping beside the mother, use of comforters and selected dietary habits to have an independent effect on caries prevalence. Dental plaque and prolonged breast feeding exerted an independent effect on caries severity and gingivitis. The strongest association with gingivitis was dental plaque.

CONCLUSIONS

In Jordan as elsewhere health promotion strategies need to be targeted to mothers from less advantaged backgrounds. Messages about infant breast feeding should emphasise that the method is beneficial to the oral health of the children if appropriately used.

The phenomenology of niche evolution via quantitative traits in a 'black-hole' sink

Previous studies of adaptive evolution in sink habitats (in which isolated populations of a species cannot persist deterministically) have highlighted the importance of demographic constraints in slowing such evolution, and of immigration in facilitating adaptation. These studies have relied upon either single-locus models or deterministic quantitative genetic formulations. We use individual-based simulations to examine adaptive evolution in a 'black-hole' sink environment where fitness is governed by a polygenic character. The simulations track both the number of individuals and their multi-locus genotypes, and incorporate, in a natural manner, both demographic and genetic stochastic processes. In agreement with previous studies, our findings reveal the central parts played by demographic constraints and immigration in adaptation within a sink (adaptation is more difficult in environments with low absolute fitness, and higher immigration can accelerate adaptation). A novel finding is that there is a 'punctuational' pattern in adaptive evolution in sink environments. Populations typically stay maladapted for a long time, and then rapidly shift into a relatively adapted state, in which persistence no longer depends upon recurrent immigration.

Evaluating web-based learning modules during an MSc programme in dental public health: a case study

The introduction of web-based learning in dentistry has raised important educational questions about the efficacy of different teaching approaches. However, studies to date have drawn conclusions that appear conflicting, or at the least, ambiguous. In this paper, it will be argued that an over-simplistic view of education and an inappropriate use of methodology have both contributed to this confusion. These points will be illustrated through the use of a case study of web-based learning in dental public health.

Caries prevalence and patterns and their relationship to social class, infant feeding and oral hygiene in 4-5-year-old children in Amman, Jordan

OBJECTIVES

To investigate the relationship between social class, infant feeding, oral hygiene, and prevalence and patterns of caries in 4-5-year-old Jordanian children.

METHOD

Two-stage random sampling procedure was used to select children enrolled in kindergartens in Amman, Jordan. Clinical examinations were carried out by one examiner. Mothers completed questionnaires relating to social class, infant feeding and the oral hygiene habits of the children.

RESULTS

Sixty-seven per cent of the children had caries; 30% had the more extensive pattern involving molars and incisors. When the significant variables were taken into account, age, social class, sleeping with the mother, use of comforter and confectionery at bed/night time were shown to be independent risk factors for caries experience. Bottle-feeding at nap/bed/night time was associated with caries in incisors and caries in incisors and/or canines. Never being breast-fed, being breast-fed for more than 18 months, being breast-fed at nap/bed/night time showed a negative association with caries confined to molars although this showed a positive association with the more extensive pattern of the disease.

CONCLUSIONS

Education for mothers about appropriate breast and bottle-feeding practices should be considered in health promotion strategies.

Food and drink consumption, sociodemographic factors and dental caries in 4-5-year-old children in Amman, Jordan

OBJECTIVE

To investigate the association between type of food and drink consumption, sociodemographic factors and prevalence and severity of caries in 4-5-year-old Jordanian children.

METHOD

Two-stage random sampling procedure was used to select children enrolled in kindergartens in Amman. Clinical examinations were carried out by one examiner. Mothers completed a questionnaire relating to sociodemographic factors and food and drink consumption.

RESULTS

Snack foods were consumed by a high percentage of children. Amongst the most popular 'high in NME sugar snacks', confectionery was reported to be regularly consumed by 76% and biscuits and cakes by 71% of them. More than 50% had carbonated drinks. Children from a lower social class, attending a kindergarten with lower tuition fees had more dessert, squashes and more teas with sugar. When all variables were considered, consumption of confectionery was independently associated with caries prevalence and consumption of teas with sugar was independently associated with caries severity.

CONCLUSION

The types of foods and drinks consumed as snacks by young Jordanian children were similar to those of Western countries. In the absence of more widespread oral health promotion measures and in the presence of high prevalence and severity of caries,the oral health of Jordanian children is a matter of concern.

Caries in preschool children in Amman, Jordan and the relationship to socio-demographic factors

OBJECTIVE

To determine the prevalence and severity of caries in children attending kindergartens in Amman and the relationship between caries experience and socio-demographic factors including age, social class based on the father's occupation, the level of mother's education and the fee level of the kindergarten attended.

DESIGN

Cross sectional survey including a dental examination of the child and a questionnaire completed by the parents.

SETTING

Kindergarten schools in Amman.

PARTICIPANTS

1,140 children including 569 4-year-olds and 571 5-year-olds.

RESULTS

Prevalence of caries in 4 year olds was 62% and in 5 year olds it was 73%. The dmft values were 3.1 and 4.1 in 4 and 5 year olds respectively. Lower caries prevalence was recorded for children of families where the father had a non-manual occupation, those whose mothers had higher levels of educational attainment and for children attending kindergartens with higher tuition fees.

CONCLUSION

Caries prevalence and severity in children attending kindergarten schools in Amman are similar to those seen in studies of children of the same age in Saudi Arabia and higher than those in children in westernised countries such as the UK. As in other countries, caries experience in young children in Amman is clearly related to social factors. Findings illustrate the need for effective oral health promotion accessible to all social groups in this middle eastern capital. Fee scale of the schools appears to be an effective measure to use in designing appropriate strategies.

Oral cleanliness, gingivitis, dental caries and oral health behaviours in Jordanian children

The aims of the study were to investigate the association between oral cleanliness, gingivitis and sociodemographic factors, dental caries and oral health behaviours amongst 4-5-year-old Jordanian children. A two stage random sampling procedure was used to select children enrolled in kindergartens in Amman. Clinical examinations were carried out by one examiner. Mothers completed questionnaires relating to sociodemographic factors and oral health behaviours. Presence of gingivitis and of four or more sites with dental plaque were seen in 66% and 83% of the children, respectively. No differences in these outcomes were seen between ages and genders. Social class and oral hygiene behaviours were important risk indicators for the level of oral cleanliness and presence of gingivitis. Higher percentages of children with four or more sites with plaque and with gingivitis had a dmft score equal or greater than four. Due to the high level of dental plaque accumulation, presence of gingivitis and their association with social class, dental caries and oral hygiene behaviours, attention should be given to the oral health of these children. In particular to the oral health of children attending kindergartens in areas of lower social class in Amman.

Clinical and photographic assessment of erosion in 2-5-year-old children in Saudi Arabia

OBJECTIVE

To compare findings from photographs of incisor teeth in pre-school children in Jeddah, Saudi Arabia to those on clinical examination for dental erosion.

BASIC RESEARCH DESIGN

Cross sectional study of 2-5-year-old Saudi Arabian children using two methods of examination.

MEASUREMENT

of erosion was carried out clinically using a scoring system and criteria based on those used in the United Kingdom national surveys. Photographs of labial and palatal surfaces of maxillary primary incisors were taken for each child and scored in the same way.

SETTING

Kindergarten schools in Jeddah, Saudi Arabia.

PARTICIPANTS

987 children from 17 randomly selected schools in Jeddah, Saudi Arabia.

RESULTS

Readable photographs were available for 727 children. Two hundred and twenty (30%) had photographic evidence of tooth tissue loss. Prevalence estimates derived from clinical examination were higher than those for photographs (36% compared to 30%). Agreement was seen between the two methods for 93% of the surfaces included.

CONCLUSIONS

Photographs have been employed in research in dentistry as well as for documentation and illustration. In epidemiology they have proved to be valuable in measuring enamel defects but have not been used for other conditions. Photographs have potential in measuring erosion, but may benefit from refinement.

Dynamical mechanism for coexistence of dispersing species

Dispersal of organisms may play an essential role in the coexistence of species. Recent studies of the evolution of dispersal in temporally varying environments suggest that clones differing in dispersal rates can coexist indefinitely. In this work, we explore the mechanism permitting such coexistence for a model of dispersal in a patchy environment, where temporal heterogeneity arises from endogenous chaotic dynamics. We show that coexistence arises from an extreme type of intermittent behavior, namely the phenomenon known as on-off intermittency. In effect, coexistence arises because of an alternation between synchronized and de-synchronized dynamical behaviors. Our analysis of the dynamical mechanism for on-off intermittency lends strong credence to the proposition that chaotic synchronism may be a general feature of species coexistence, where competing species differ only in dispersal rate.

The relationship between erosion, caries and rampant caries and dietary habits in preschool children in Saudi Arabia

OBJECTIVES

The aim of this study was to investigate the possible association between dental erosion and caries, and variables including socio-economic status, reported dietary practices and oral hygiene behaviour, in a sample of children in Jeddah, Saudi Arabia. A cross-sectional study including dental examination and questionnaire survey was carried out at a number of kindergartens.

SAMPLE AND METHODS

A sample of 987 children (2-5-year-olds) was drawn from 17 kindergartens. Clinical examinations were carried out under standardized conditions by a trained and calibrated examiner (MAM). Information regarding diet and socio-economic factors was drawn from questionnaires distributed to the parents through the schools. These were completed before the dental examination.

RESULTS

Of the 987 children, 309 (31%) showed signs of erosion. Caries were diagnosed in 720 (73%) of the children and rampant caries in 336 (34%). Vitamin C supplements, frequent consumption of carbonated drinks and the drinking of fruit syrup from a feeding bottle at bed- or nap-time when the child was a baby, were all related to erosion. Consumption of carbonated drinks and fruit syrups was also related to caries but they were part of a larger number of significant factors including socio-demographic measures and oral hygiene practices.

CONCLUSIONS

There was no clear relationship between erosion and social class, or between erosion and oral hygiene practices; the reverse was true for caries. Dietary factors relating to both erosion and caries and/or rampant caries were found in this sample of children.

Advances in dental public health

Dental public health has been defined as 'the science and art of preventing oral diseases, promoting oral health and improving the quality of life through the organised efforts of society'. Dental practitioners most often have the oral health of individual patients as their primary focus but the aim of public health is to benefit populations. Early developments in dental public health were concerned largely with demonstrating levels of disease and with treatment services. With greater appreciation of the nature of oral health and disease, and of their determinants has come recognition of the need for wider public health action if the effects of prevention and oral health promotion are to be maximized.

Dynamical mechanism for coexistence of dispersing species without trade-offs in spatially extended ecological systems

Most prior studies on the role of dispersal in the coexistence of competing species have emphasized the need for trade-offs between competitive and colonizing abilities for coexistence. Theoretical studies of the evolution of dispersal recently have revealed an alternative mechanism for the coexistence of species differing solely in dispersal rates in spatially extended systems. We present an analysis and numerical evidence indicating that chaotic synchronism, occurring in an extremely intermittent form, is an important feature of the spatiotemporal variation in fitness required for the coexistence of species without trade-offs.

Dental treatment under general anaesthesia at a hospital in Jeddah, Saudi Arabia

Dental General Anaesthesia (DGA) has been shown to be of value in providing both restorative treatment and extractions in children who are unable to accept this using other methods of management.

AIMS

The aims of this retrospective study were to determine the characteristics of patients attending for treatment under DGA at a centre in Saudi Arabia, to describe the type of dental treatment carried out using DGA and in the subsequent 3-year period.

SAMPLE AND METHOD

Data were collected from hospital records of 555 patients who received treatment under DGA at King Fahad Hospital in Jeddah, Saudi Arabia, between 1995 and 1997.

RESULTS

Ninety three percent of the patients were aged 8 or younger at the time of DGA, with 43% being under 5 years of age. The main indications for use of DGA in the youngest age group were dental management of rampant caries (77% of the youngest age group) and inability to accept treatment under local anaesthesia (49% of those aged 5-8 years). Seventy percent of patients had treatment involving both extractions and restorative care, and the majority, 81%, had one tooth or more restored with preformed metal crowns. Sixty-three percent of patients attended for recall after 6 months but only 10% did so after a 3-year interval. Only one of the 555 patients received a second DGA at the same centre during the 3 years following treatment.

CONCLUSIONS

The service studied provides dental treatment primarily for children with extensive disease. Failure to attend for recall was common, suggesting that preventive methods which rely on regular attendance may not be successful in this group of children.

Investigation of an index to measure tooth wear in primary teeth

Tooth wear, in particular erosion, has been reported to be widespread in children in the UK. Wear may affect either dentition, but epidemiological measurement has proved difficult.

OBJECTIVES

The objectives of this study were: (a) to investigate use of a simple index of wear in primary teeth; and (b) to compare findings from visual examination and from photographs with those at histological examination of the same teeth.

SAMPLE AND METHODS

Forty-one exfoliated or extracted primary anterior teeth were assessed visually and using photographs. Ground sections of the teeth were prepared and examined using polarised light microscopy.

RESULTS

On visual examination, 31 of the 41 teeth had evidence of wear. In 14 teeth, tissue loss was confined to enamel and in 17 it extended into dentine. Findings on photographs were very similar to those on visual examination. Of the 10 teeth without erosion visually, two had evidence of loss on histological examination. Of the 14 with visual evidence of erosion confined to enamel, dentine was exposed in 11 cases. Diffuse demineralisation was evident histologically in 11 of the 31 teeth with evidence of erosion.

CONCLUSIONS

It was concluded that clinical assessment of erosion may underestimate the extent of the condition. Under the conditions of the study, photographs gave results similar to those on visual examination.

Oral health status and access to care in a rural area of India

A study was carried out in two villages in a rural area of Andhra Pradesh, India, 150 kilometres south of the state capital, Hyderabad. Ninety-eight women and sixty-two men, age range 15-70 years, were interviewed and examined. Information gathered included socio-economic data, distance travelled outside the village and previous access to health care. Data were recorded on periodontal status using CPITN and full periodontal charting. Comparisons were made between male and female subjects for travel outwith the village, attendance at medical and dental health facilities, tooth cleaning methods and materials and prevalence of periodontal disease. There was a high prevalence of chronic inflammatory periodontal disease in this population, and most of this was untreated. In view of the difficulties in access to health care, it would be prudent to offer good preventive oral health care within the rural community.

Caries and its association with infant feeding and oral health-related behaviours in 3-4-year-old Brazilian children

OBJECTIVES

To investigate the relationships between socio-demographic factors, infant feeding habits, oral hygiene and the prevalence and patterns of caries in Brazilian 3-4-year-olds.

METHODS

Systematic random sampling was used to select children enrolled in municipal nurseries in Araraquara, Brazil, in 1998. Clinical examinations were carried out by one examiner using dmft and dmfs indices and WHO criteria. Questionnaires for information related to the socio-demographic background, oral hygiene and dietary history of the children were completed by their mothers.

RESULTS

Caries was seen in 46% of the children; 17% of them had the more extensive pattern involving molars and incisors. Social class, mother's education, and age at which breast-feeding terminated showed statistically significant associations with caries. Feeding bottles with added sugars were still being given to 80% of the children. When the significant variables were taken into account only age at which breast-feeding terminated showed a significant relationship to the pattern of disease. Children who were never breast-fed or were breast-fed beyond the age of 24 months had a higher prevalence of the more extensive pattern of caries.

CONCLUSIONS

The association between the length of time a mother breast-feeds and extensive caries should be a consideration in any local infant feeding policies or health promotion strategies. The duration for appropriate breast- or bottle-feeding should be emphasised.

Prevalence of caries and developmental defects of enamel in 9-10 year old children living in areas in Brazil with differing water fluoride histories

AIMS

To assess the prevalences of caries, of developmental defects of enamel and their interrelationship in Brazilian 9-10-year-olds from areas of contrasting fluoridation histories.

METHODS

Systematic random sampling procedures were used to select children from an area where water had been fluoridated in 1963 and from a second area where water had been fluoridated since 1998. Clinical examinations for caries were carried out using the DMFT index and WHO diagnostic criteria. Developmental defects of enamel on upper incisors were diagnosed using the DDE index.

RESULTS

A difference of 40% in DMFT was observed, with a lower prevalence of disease in the area fluoridated since 1963. Diffuse opacities affected 14.3% of the children from the area fluoridated since 1963 compared with only 2.4% in the area fluoridated in 1998. Children living in the area fluoridated in 1963 who had diffuse defects had twice the chance of being free from caries compared with those living in the same area who had no defects or who had only demarcated or hypoplastic defects.

CONCLUSIONS

This study confirms previous ones in showing the benefits of water fluoridation. Diffuse opacities of upper incisors affected relatively few subjects in either of the two areas.

A retrospective study of unerupted maxillary incisors associated with supernumerary teeth

We retrospectively reviewed the clinical records and radiographs of 100 patients who had had supernumerary teeth removed. Their mean (SD) age was 9 years 3 months (2). The 100 patients had a total of 127 unerupted maxillary incisors associated with supernumerary teeth. The supernumerary tooth was removed without exposure of the permanent tooth more often among the 79 younger children (aged 10 years or less) (SND=3.52, P<0.01), and when the incisors were less mature (Cvek classification 1, 2, and 3) (SND=5.27, P<0.01). Of these incisors with immature roots that were treated conservatively, 60 (72%) erupted and 24 (28%) required further operation. Of the mature incisors treated conservatively, 10 (63%) required further operation. In this study, almost three-quarters of immature incisors erupted spontaneously after removal of the associated supernumerary teeth. Over half of the mature teeth required further operation. Mature teeth should be exposed with or without bonding at the time of removal of the supernumerary teeth.

Provision of dental general anaesthesia for extractions in child patients at two centres

AIM

To two contrasting centres, to describe the provision of dental general anaesthesia (DGA) for simple non-surgical extractions in terms of the type of treatment provided, including the number of primary and permanent teeth extracted, and the characteristics of child patients attending in terms of their age group and gender.

DESIGN

Retrospective analysis of hospital records.

METHOD

Data were drawn from records of services over a 12-month period in 1996/97 at: a) a London dental hospital (Centre 1), and b) in the community dental services in Rochdale, Lancashire (Centre 2). Information was collated and analysed using the SPSS statistical software package.

RESULTS

The majority of patients at both centres were aged less than 9 years. Almost one third (31%) of those seen at Centre 1 were below 5 years of age, but fewer of this age group were treated at Centre 2. Children aged 9 years or less had an average of 5.4 (SD = 3.0) primary teeth extracted at Centre 1 and 3.0 (SD = 2.0) at Centre 2. For permanent teeth, an average of 3.2 (SD = 1.2) and 2.7 (SD = 1.4) were extracted at Centres 1 and 2 respectively.

CONCLUSIONS

Both services were used primarily for the extraction of primary teeth although the services differed in the ages of patients who used them and in the numbers of teeth extracted. Numbers of patients attending the service at Centre 1 had declined over time but numbers of teeth extracted per child had increased.

The effects of density dependence and immigration on local adaptation and niche evolution in a black-hole sink environment

We examine the effects of density dependence and immigration on local adaptation in a "black-hole sink" habitat, i.e., a habitat in which isolated populations of a species would tend to extinction but where a population is demographically maintained by recurrent one-way migration from a separate source habitat in which the species persists. Using a diploid, one-locus model of a discrete-generation sink population maintained by immigration from a fixed source population, we show that a locally favored allele will spread when rare in the sink if the absolute fitness (or, in some cases, the geometric-mean absolute fitness) of heterozygotes with the favored allele is above one in the sink habitat. With density dependence, the criterion for spread can depend on the rate of immigration, because immigration affects local densities and, hence, absolute fitness. Given the successful establishment of a locally favored allele, it will be maintained by a migration-selection balance and the resulting polymorphic population will be sustained deterministically with either stable or unstable dynamics. The densities of stable polymorphic populations tend to exceed densities that would be maintained in the absence of the favored allele. With strong density regulation, spread of the favored allele may destabilize population dynamics. Our analyses show that polymorphic populations which form subsequent to the establishment of favorable alleles have the capacity to persist deterministically without immigration. Finally, we examined the probabilistic rate at which new favored alleles arise and become established in a sink population. Our results suggest that favored alleles are established most readily at intermediate levels of immigration.

The Coexistence of Competing Parasites. Part II-Hyperparasitism and Food Chain Dynamics

Hyperparasitism is a widespread interaction in natural communities, but has to date received little attention in the theoretical literature. In this paper, we compared canonical models for food chains (resource-prey-predator systems) and host-parasite-hyperparasite interactions. We focus on microparasites, so the dynamical variables are the abundances of host individuals in different classes (e.g. with or without a particular parasite), and assume that the parasite is the only factor regulating a host population. Analysis of a "donor-controlled" model in which the primary parasite regulates host population growth, but with no additional demographic impact of the hyperparasite, suggests that intrinsic growth rate r of the host population is a fundamental parameter governing persistence of the hyperparasite. We then examine a model in which the hyperparasite can affect host births, deaths, and rate of recovery from the primary parasite. A wide range of outcomes are possible. For instance, hyperparasites can stabilize inherently unstable host-parasite systems, or destabilize stable systems. Persistence at a stable equilibrium often requires that the host intrinsic growth rate r lie within defined bounds; at low r, the hyperparasite may not be able to persist (in stable systems), whereas at high r the system is unstable and the host population grows in an unbounded fashion. We conclude by sketching directions for future work, and suggesting some possible practical implications of our results.Copyright 1998 Academic Press

Comparison of two indices of caries patterns in 3-6 year old Brazilian children from areas with different fluoridation histories

The purpose of this study was to define the pattern of caries in 3-6 year old children from two districts in Araraquara, SP, Brazil, fluoridated for more than 10 years and from a much more recently fluoridated one in the same city, using two different indices. The study included 1,066 children (903 from the two first districts and 163 from the third). Patterns of disease were described in terms of prevalence and dmft in molars, incisors (and/or canines) individually and together. Pattern was also described according to the 'caries analysis system'. In both areas the majority of 3-4 year olds had disease confined to primary molars. In the areas fluoridated for more than 10 years, the highest proportion of 5-6 year olds with caries also had the disease confined to primary molars (36 per cent) but in the more recently fluoridated area, similar proportions of children had caries in primary molars alone as had caries in both primary molars and incisors (40 per cent and 44 per cent, respectively). Results according to the 'caries analysis system' showed that in both areas the prevalence of fissure caries and posterior bucco-lingual surface pattern in 5-6 year olds were twice as great as those observed in 3-4 year olds. Differences between the areas were obvious whichever method was used to define pattern, confirming the benefits of water fluoridation. The simpler method of grouping tooth type affected showed the differences as effectively as the more complex 'caries analysis system'.

Prevalence and severity of caries in 3-12-year-old children from three districts with different fluoridation histories in Araraquara, SP, Brazil

OBJECTIVE

To determine the prevalence and severity of caries in 3-12-year-old children in three districts of the city of Araraquara.

DESIGN

An epidemiological survey was carried out by trained and calibrated examiners in 1995 and 1996, using the WHO diagnostic criteria.

SETTING

Two districts, Araraquara and Vila Xavier had been fluoridated since 1963 and one, Gavião Peixoto, since 1994.

SUBJECTS

The study included 1,191 children from Araraquara, 653 from Vila Xavier and 652 from Gavião Peixoto.

OUTCOME MEASURES

Prevalence of caries, dmft, dmfs, DMFT and DMFS indices.

RESULTS

Results showed moderate caries experience in all three districts. Differences between districts in relation to fluoridation history were particularly obvious in primary teeth. In 3-4-year-old children, one third of those in Araraquara and Vila Xavier had some caries experience compared to 58% in Gavião Peixoto. In permanent teeth, 20% or less of the mean DMFT was made up of untreated decay in Araraquara and Vila Xavier whereas in Gaviao Peixoto it made up between 50 and 57% of values in 7-12-year-old children.

CONCLUSIONS

The prevalence and severity of caries was lower in dentitions of children from the districts fluoridated since 1963. Improvements are likely in the future in Gavião Peixoto as the benefit of fluoridation continues but additional means of promoting oral health are needed in all three districts.

Developments in fluoride toothpastes--an overview

OBJECTIVE

This paper reviews current issues in the development of fluoride toothpastes as a public health measure.

DESIGN

The issues examined included low concentration formulations, delivery systems, dispensing instructions and labelling, oral clearance. effect on root caries, additional therapeutic agents and marketing and manufacturing issues.

RESULTS

Lower fluoride formulations may carry a lower risk of fluorosis but this must be balanced against a higher risk of caries. Risk factors for fluorosis include inappropriate fluoride supplements but the age at which toothbrushing began, frequency of brushing and residence in an optimum fluoride area have also been implicated.

CONCLUSIONS

The dental profession should: clarify the most appropriate fluoride concentration in toothpastes used for children; ensure that other sources of fluoride do not increase the risk of dental fluorosis: investigate the effectiveness of fluoride toothpaste in inhibiting root surface caries in adults. Manufacturers should: continue to improve the performance of fluoride toothpaste; ensure that all pastes maximise fluoride bioavailability; develop active agents to help reduce oral disease; label products clearly with ppm F; review the delivery systems so as to reduce the risk of dental fluorosis.

The influence of audit on the diagnosis of occlusal caries

Audit is widely used to improve the quality of care in both medicine and dentistry but has not always been subject to systematic evaluation. The aim of this study was to assess the effect of an audit exercise on the diagnosis of occlusal caries. Using combined visual and radiographic methods. 11 dentists assessed 60 extracted molars for occlusal caries on two occasions. An audit exercise, in the form of a meeting, was carried out in the intervening period. Inter- and intra-examiner reproducibility were estimated for each of the two examinations. Validation was through a gold standard set up by sectioning the teeth. Wide diagnostic disparity was seen at both examinations, all inter- and intra-examiner kappa values were below 0.73. Intra-examiner kappa values increased significantly on the second occasion. Mean sensitivity and specificity were 0.65 and 0.74, respectively, at the first examination and 0.65 and 0.72 at the second. No changes were seen that could be attributed directly to the audit exercise but practising the diagnostic test appeared to be beneficial to intra-examiner reproducibility of diagnosis.

Caries in pre-school children in Camden 1993/94

Previous surveys carried out in the inner city area of Camden between 1966 and 1986 gave indication of a deterioration in dental health in pre-school children during the 1980s. Four hundred and six children were included in the current survey, which used the same sampling and methodology as previously. The aims of the present survey were to determine the current prevalence of caries and of rampant caries and to relate prevalence to social factors, to infant feeding habits and to the use of sweetened comforters, and to determine the extent of dental care received. Caries affected 11% of 2-year-old children and 29% of 3-year-olds, rampant caries affected 6% and 14% respectively. A higher likelihood of caries occurred in children of Asian origin and those given a sweetened comforter. For rampant caries, likelihood was greater amongst those of Asian origin and those given a sweet drink in a bottle for 2 years or longer. Comparison with results of the last study provides little evidence of improvement in dental health in young children in this low fluoride area, with a small proportion suffering relatively severely from caries.

The national diet and nutrition survey of 1.5 to 4.5 year old children: summary of the findings of the dental survey

A dental health survey was included as part of a large scale study of nutrition in preschool children. The survey was carried out in 1992/93 and was published in spring 1995. Information on dental health status and on dietary intake was gathered from a total of 1658 children from 100 geographical sectors in the United Kingdom. This article summarises the main findings and highlights some of the most important findings regarding dental health and its relationship to dietary factors. Seventeen per cent of children had some caries experience and in 83% of cases this was untreated. Dental decay was most strongly related to social background. The factors most strongly related to caries prevalence were: receipt of income benefits, in the 1.5-2.5-year-old children; the educational status of the mother in the 2.5-3.5-year-old children and social class of the head of household in the 3.5-4.5-year-old children. Consumption of sugary drinks at bedtime, children being left to brush their teeth themselves, household expenditure on confectionery and geographical region were also strongly associated with caries prevalence.

The weaning diet and dental health

Weaning practice can have a major influence on both immediate and future dental health and good dietary practices from birth have the potential to secure a healthy dentition for life. In a recently published report it is recommended that infants (an infant may be defined as a child who has not yet reached the age of one year) be weaned on foods and drinks free as far as possible of non-milk extrinsic (NME) sugars. At the same time, there has also been an increasing development of low-sugar and sugar-free products for infants. There has also been growing concern that infant drinks with low pH may cause enamel erosion in primary teeth, a phenomenon that is perhaps more widespread than has been recognised in the past. The aim of the weaning diet is to achieve a diet which fulfills nutritional requirements for the growing child and which contains a wide variety of foods and drinks. It is suggested that items high in NME sugars are not a necessary part of the diet, should be regarded as 'occasional', and not given every day. Drinks other than milk or water should constitute a minority of total drinks and be given only at main mealtimes; they should not be given in bottles or at bedtime.

Fissure sealants: a 4-year clinical trial comparing an experimental glass polyalkenoate cement with a bis glycidyl methacrylate resin used as fissure sealants

The 4-year results of a fissure sealant trial are reported. Glass polyalkenoate and bis GMA sealant were applied to 590 first permanent molar teeth using a half mouth study design in a group of 228 6-8-year-old children. Similar cariostasis was observed for the two materials at the end of 4 years despite marked differences in retention. Polyalkenoate cements probably should be regarded as 'fluoride depot' materials rather than fissure sealants when used in this context.