Journal of Investigative and Clinical Dentistry (2011), 2, 223–228
REVIEW ARTICLE Community Dentistry
Risk factors for early childhood caries in disadvantaged populations Amit Arora1, Eli Schwarz2 & Anthony Stevenson Blinkhorn1 1 Department of Population Oral Health, Faculty of Dentistry, The University of Sydney, Sydney, NSW, Australia 2 Department of Community Dentistry, School of Dentistry, Oregon Health and Science University, Portland, OR, USA
Keywords dental caries, disadvantaged population, early childhood caries, preschool children, risk factor. Correspondence Dr Amit Arora, Population Oral Health, Faculty of Dentistry, The University of Sydney, 1 Mons Road, Westmead, NSW 2145, Australia. Tel: +61-2-8821-4371 Fax: +61-2-8821-4366 Email: [email protected]
Received 27 February 2011; accepted 26 March 2011.
Abstract Early childhood caries is a significant international public health problem. The aim of this paper was to review the current evidence of the risk factors for dental caries in disadvantaged children under 6 years of age. Medline, Cochrane, and PubMed database searches were conducted. Systematic reviews were used where available, or meta-analyses; randomized, controlled trials; and cohort, case-control, and cross-sectional studies (in that order). Studies were restricted to those published in English from 1990 to October 2010. Early childhood caries has a complex etiology with biological, behavioral, and sociodemographic influences. Evidence suggests that young children are most likely to develop caries if Streptococcus mutans is acquired at an early age, although this is influenced by other factors, such as oral hygiene, fluoride, diet, dental visit patterns, socioeconomic status, ethnicity, and health literacy. Etiological pathways should be taken into consideration when designing interventions to prevent dental caries in disadvantaged preschool children.
Introduction Primary (baby) teeth serve multiple roles, such as chewing food, preserving space for permanent teeth, development of speech, and an attractive smile, which is linked to selfesteem. Despite improvements in oral health, dental caries is identified as one of the most prevalent chronic diseases of early childhood.1–3 Dental caries is a bacteria-mediated transmissible disease of multifactorial etiology, characterized by the demineralization and destruction of tooth enamel, dentine, and ultimately infection of the pulp. The onset of dental caries has five necessary components: cariogenic bacteria (predominantly mutans streptococci), fermentable carbohydrates (the substrate), susceptible teeth (the host), lack of fluoride, and time for the disease to develop. Although the literature on the etiology of dental caries is extensive, little is known about the development of dental caries in early childhood.4 This point is highlighted by the fact that researchers have struggled to clearly define dental caries in preschool children. It has been referred to by many different names,5 ª 2011 Blackwell Publishing Asia Pty Ltd
and this has led to problems in comparing the international epidemiological data on caries prevalence.6 In 1999, a US Government-sponsored workshop addressed this issue, and defined early childhood caries (ECC) as the presence of one or more decayed, missing (due to caries), or filled surfaces on any primary tooth in children up to 71 months of age.7 ECC is a rapidly-progressing, debilitating disease, and is characterized by childhood distress, repeat prescriptions of antibiotics, severe pain, sepsis, and sleep loss.3 The longterm consequences of ECC might include reduced growth, nutritional and sleep problems, as well as the potential to disrupt family life.8 Many dental services are faced with preschool children with dental pain who are difficult to treat, and clinical care under general anesthetic is often the only practical option for pain relief and for dealing with carious teeth.3 ECC is an international public health problem.1–3 In 1996, 39% of Australian 6-year-old children had dental caries,9,10 and since that time, the caries experience in Australian children in all states and territories has increased.10,11 The 2002 Child Dental Health Survey of 223
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Australia reported that 45% of 5 year olds had one or more decayed or missing teeth, and 10% of those children examined were found to have more than seven decayed teeth.12 The problem is not unique to Australia. In the UK, successive national child dental health surveys have shown little change in caries prevalence in 5-year-old children over the last 20 years.13 Data from the USA tell a similar story; from 1988 to 1994, and from 1999 to 2002, there was no change in the prevalence of dental caries among children aged 2–11 years.14 Caries rates in industrialized countries are higher among the more socially disadvantaged,15–17 particularly for children who are refugees or migrants, or whose parents are refugees or migrants from a non-English-speaking background.18 The prevalence of ECC in developing countries and disadvantaged populations within developed countries can be as high as 70%.6 This can arise from socioeconomic disadvantage, social exclusion, sociocultural differences in oral health beliefs and practices, and low health literacy.19–22 The high levels of dental disease are important in dispelling the myth that oral health problems are largely solved, and that future investments in dental care and health promotion are not warranted. However, there is little agreement as to the most effective interventions to prevent ECC. Fisher-Owens et al.23 proposed a model with individual-, family-, and communitylevel influences on the oral health of young children, which incorporates five key domains, namely: genetic and biological factors, the social environment, the physical environment, health behaviors, and dental/medical care. However, these domains should be used with care, as there is considerable overlap of the physical environment and dental/medical care with the other three domains. The objective of this review is to investigate the current evidence base in relation to the etiology of dental caries in disadvantaged children under the age of 6 years, in order to provide an evidence base to inform health service personnel planning interventions to control the problem. Methods This review was undertaken to delineate the mechanisms involved in the etiopathogenesis of ECC, so that effective future preventive programs could be developed for disadvantaged communities. The following databases were searched: Cochrane Central Register of Controlled Trials (CENTRAL), Medline (Ovid), and PubMed. Sensitive search strategies were developed using a combination of free text and controlled vocabulary, with the assistance of a highly-experienced librarian to identify the best-available evidence. Systematic reviews were used where available, and in their absence, meta-analyses; randomized, controlled trials; cohort studies; case-control studies; and 224
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cross-sectional studies were used, in that order. The studies were restricted to those published in English that reported on children under the age of 6 years, and were published from 1990 to October 2010. No specific hand searching was undertaken. The findings of the literature are presented under three headings: biological issues, behavioral issues, and sociodemographic influences in ECC. Biological issues in ECC Streptococcus mutans (SM) and lactobacilli are the predominant microorganisms in the development of ECC.4,8,24–27 SM has been associated with the development of early carious lesions,24–26 and lactobacillus has been associated with the progression of lesions into the dentine.27 The cariogenic bacteria can: (a) transport sugars and convert them to acid (acidogenic); (b) produce extracellular and intracellular polysaccharides that contribute to the plaque matrix and enable the bacteria to adhere to one another and to the tooth surface, probably via specific receptors; and (c) thrive at a low pH.28,29 The age at which the child is infected with SM is important in determining the caries risk of the child.4,30 Historically, it was believed that mutans streptococci required a non-shedding surface for colonization, and it was hypothesized that they were unable to colonize a predentate infant,31 as researchers did not find SM until the primary teeth erupted.32 In addition, it has become evident that the ‘‘window of infectivity’’ for the colonization of SM is between the age of 19 and 31 months.33 However, research from the USA raises doubt on the accuracy of the ‘‘window of infectivity’’, as SM has been detected in toddlers under the age of 19 months.34 In addition, recent research from Australia supports these findings that predentate infants can be colonized with SM.35,36 The factors associated with early colonization were sweetened fluids taken to bed, frequent sugary snacks, sharing foods with adults, and maternal SM levels.35 A recent systematic review that investigated the relationship between SM and ECC concluded that SM is a strong risk indicator for ECC,37 and data from longitudinal studies are now emerging, showing that SM is the key determinant of ECC.35 The main defense against SM-induced dental caries is the fluoride from toothpaste or water and saliva. Fluoride encourages remineralization of damaged enamel and interferes with the bacterial metabolism. Saliva reduces dental caries by buffering plaque acids, the presence of immunoglobulins, and increased flow rates when eating.4,38 In addition, it is a reservoir for calcium and phosphate minerals, which aid in the remineralization of the enamel.38 Upon eruption, teeth have immature enamel and are most susceptible to dental decay.39 However, with time, ª 2011 Blackwell Publishing Asia Pty Ltd
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the tooth enamel matures after incorporating minerals from the mouth, including fluoride.39 Many studies have also found an association between developmental defects of teeth, such as enamel hypoplasia, and dental caries.40–43 Behavioral issues in ECC Dental caries is related to family norms of behavior, especially a child’s feeding habits, toothbrushing frequency, exposure to fluoride, and dental visits. Feeding habits There is a wealth of evidence that demonstrates a relationship between fermentable carbohydrates in the diet and dental caries.44 The relationship between sugar consumption and caries experience is largely dependent on the frequency of sugar consumption.45 A systematic review concluded that the relationship between sugar consumption and dental caries is not as strong as it was in the prefluoride era; however, the restriction of sugar consumption has an important role in caries prevention, especially in young children with immature enamel.46 Although non-milk extrinsic sugars differ very little in their acidogenic potential, sucrose is the most common product in most food and drinks, and it is readily fermented by SM.45 A systematic review on ECC has shown that the manner and form in which sugar is taken, and the frequency of consumption, are more important than the absolute amount of sugar consumed.30 Drinks, such as fruit juices and carbonated drinks, are an increasingly important source of sucrose in the diet of young children,47 and their consumption is associated with dental caries in the primary dentition.48,49 There is some debate as to whether infant formula or bovine milk in bottles and breast milk given frequently to young children contribute to the development of ECC. The proposed relationship is based on the fact that the lactose in milk is available for fermentation by SM. Compared to bovine milk, breast milk has a lower mineral content, higher concentration of lactose, and lower protein content, but these differences are insignificant in terms of its effect on oral health.5 Although prolonged or on-demand breast-feeding has been suggested as an etiological factor for dental caries,50 there is limited published evidence to support this supposition.51 However, many researchers have reported an association between ECC and prolonged/night-time bottle-feeding.52–55 These studies examined bottle use in children aged 12–24 months, and suggest that continued bottle use after a child’s first birthday is associated with ECC, but factors, such as duration of the habit and the content in the bottle, are crucially important. ª 2011 Blackwell Publishing Asia Pty Ltd
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Toothbrushing and exposure to fluoride It is well established that toothbrushing is included in the primary socialization process, and most parents want to make sure their child’s teeth are brushed at least once a day. While toothbrushing is an important habit to encourage, its key influence on caries is to introduce fluoride from toothpaste onto the enamel surfaces. Fluoride is a highly-effective agent that remineralizes early lesions and acts to strengthen the surface dental enamel by forming fluorapatite. Brushing without fluoride will not prevent the majority of carious lesions. However, Reisine and Psoter56 suggest that it is difficult to distinguish whether the effect of toothbrushing is a measure of fluoride application or whether it is the result of the mechanical removal of plaque. Featherstone57 states that the caries process is a delicate balance between demineralization and remineralization, and in the mouth there is a ‘‘see-sawing’’ between these two phenomena. Children not exposed to fluoridated water and not using fluoride toothpaste are more likely to have dental caries.58–62 There is convincing evidence that brushing with a fluoride toothpaste is the most significant factor in the decline of dental caries in many developed countries since the 1970s.58,62–65 Studies have reported that the onset of caries is more likely when the children start brushing at a later age.58,66 Furthermore, there is sufficient evidence to show children who brushed their teeth less frequently are more likely to have ECC.23,24,30,42,58 A systematic review by Harris et al.30 suggests that brushing less than once per day, no parental supervision of toothbrushing, not brushing at bed time, and not using fluoride toothpaste are the main risk factors for ECC. Apart from brushing with a fluoride toothpaste, there is well-established evidence that children living in areas without fluoridation of public water supplies have a higher prevalence of ECC.67 Dental visits Dental care is one of the most unmet health needs of young children in the USA, which makes disadvantaged populations at greater risk of poor oral health.68 Although it is recommended that children should have their first dental visit by 12 months of age,69 data from the USA indicate that only approximately 9% of 3–4 year olds are taken to a dental professional.70 In Australia, less than 40% of children aged 3–4 years are taken to a dental professional.71 Data from Australia show that young children with private health insurance were more likely to have a dental visit, and disadvantaged children have less frequent dental visits.71 The lack of dental visits might be due to the costs involved. Despite the fact that dental visits before the age of 3 years is low, contact with general medical practitioners and child family health nurses is 225
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high. Dental professionals should work with other primary health-care providers and screen early signs of dental decay and provide anticipatory advice to reduce the incidence of ECC.
outcomes in general and oral health.76 Clinicians need to be aware of the major impact health literacy makes on all aspects of health care, particularly when giving preventive advice or information.
Sociodemographic influences in ECC
Three major sociodemographic factors have been associated with the risk of ECC: socioeconomic status (SES), ethnicity, and health literacy. SES is usually a composite of the level of education, family income, and occupation.72 One of the limitations, from a public health research perspective, is the lack of consensus on how to define SES.56 Despite this academic disagreement, social disadvantage is a strong predictor for dental caries.22,30,56,73 Sheiham and Watt74 argue that the main cause of inequalities in oral health are due to differences in patterns of consumption of non-milk extrinsic sugars and the daily use of fluoride toothpastes. In addition, children raised in ethnic minority communities are at an increased risk of ECC,30 but it is difficult to separate cultural influences of ethnicity from the parameters suggested by Sheiham and Watt.74 Literacy can be defined as ‘‘the ability to understand and employ printed information in daily activities in order to achieve one’s goals and develop one’s knowledge potential’’.75 Health professionals, in general, tend to overestimate the reading skills of patients. For example, a recent survey75 showed that approximately 20% of Americans and 17% of Canadians have difficulty reading simple English prose. More recently, it was reported that individuals with lower levels of health literacy have poor
A wide range of risk factors are associated with ECC in children from disadvantaged backgrounds. However, the strength of association is highly variable. Although caries is classed as an infectious disease caused by SM, the absolute link to ECC is one of conjecture. The influence of other factors clearly modifies how the dental hard tissues react to the acidic byproducts produced by SM. The key points to address are behavioural and cultural issues, which will influence family behaviors in such a way as to encourage or reduce the risk of ECC. The importance of a child’s family environment is evident from the work of Milsom et al.,77 who reported that a young child with one carious lesion is five times more likely to develop more carious lesions than a child who is caries free. This finding highlights the importance of population prevention programs to maintain a healthy oral environment as the teeth erupt.
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Acknowledgments We are grateful to Mr Jeremy Cullis for his assistance in developing the search strategies. Dr Amit Arora was supported by the Oral Health Foundation and University of Sydney International Research Scholarship to conduct this review.
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