Fluoride and Dental Caries Prevention in Children

After completing this article, readers should be able to:Fluoride is a valuable caries prevention modality that has a large body of evidence supporting its use. Because infants, young children, and their parents typically visit the pediatric office many times before ever seeing a dentist, parents may bring questions about fluoride to their pediatricians. Moreover, health supervision visits provide unique opportunities for pediatricians to address fluoride in the context of preventive oral health. However, until recently, pediatricians typically received little training in oral health and therefore may need additional education about fluoride to answer parents’ questions, counter misinformation, and ensure appropriate use of fluoride among their patients. Given that approximately one-quarter of US children younger than 5 years have caries, it is particularly important that pediatricians are knowledgeable about fluoride and comfortable with delivering it to their patients.Fluoride is highly effective in preventing dental caries (commonly known as dental decay), with both primary and secondary preventive properties. By definition, primary prevention precedes the onset of disease so that disease is avoided. An example of primary prevention is regular consumption of fluoridated water, which provides adequate topical exposure to fluoride to prevent dental caries. Secondary prevention involves early identification of caries so it can be arrested or reversed. An example is fluoride varnish (FV) application to white spot lesions, which are the white, chalky spots at the gingival margins that are the first visible evidence of caries. FV remineralizes these areas and reverses the decay process.Caries begins in childhood and eventually affects 90% of adults. Even so, dental decay’s effect on low-income individuals is disproportionate, leading to earlier onset, more affected teeth, complications, and ultimately teeth lost during adulthood because of caries. Results of the National Health and Nutrition Examination Survey (NHANES) III during 1999–2004, indicated that 24% of 2- to 4-year-olds and 51% of 6- to 8-year-olds had caries in primary teeth. (1) Among 12- to 19-year-olds, 59% had caries in permanent teeth. Children living below 200% of the federal poverty level (FPL) had more caries relative to children at or above 200% of the FPL (Figure 1). (1) Caries prevalence has decreased over time in all age categories, but this trend recently reversed for 2- to 4-year-olds, with a 5% increase (from 19% to 24%) since 1988–1994 (NHANES II). (1) The reasons for this increase are unclear.The proportion of US children with untreated caries has remained approximately the same since 1988–1994. In 1999–2004, 16% of 2- to 4-year-olds and 28% of 6- to 8-year-olds had untreated caries in primary teeth, whereas 20% of 12- to 19-years-olds had untreated caries in permanent teeth. (3) Children living below 100% of the FPL had 2 to 3 times as many untreated caries as children living above 200% of the FPL. (3) Insurance and income-based disparities in access to dental care are important contributors to these differences in untreated caries. (4)(5) Despite mandated dental care coverage for low-income children under the Early and Periodic Screening, Diagnosis, and Treatment (EPSDT) program (6) and, more recently, the State Children’s Health Insurance Program (7) and the Children’s Health Insurance Program Reauthorization Act, (8) it remains difficult for publicly insured children to access professional dental care, in part because fewer dentists accept Medicaid. (9) In 2008, just 38% of Medicaid-enrolled children, ages 2 to 18 years, received dental care in the previous year. (9)Untreated caries can lead to toothache and other more serious medical problems. In 2008, approximately 15,000 US children presented to emergency departments with toothache cited as the reason for their visit. (10) Some of these children required hospital admission and/or surgery. In a well-publicized case in 2007, a Maryland boy died of complications resulting from dental caries. (11) Analysis of the 2007 National Survey of Children’s Health documented that 14% of elementary school children had experienced toothaches in the previous 6 months. (12) Being from a low-income family, of minority race, or having special health care needs independently increased risk of toothache. (12)Dental decay is a transmissible infectious disease in which cariogenic bacteria are passed from mother (usually) to child. Streptococcus mutans and Lactobacillus species, among other bacteria, produce acids as end products of carbohydrate metabolism. These acids dissolve the calcium-phosphate mineral of a tooth’s enamel during a process called demineralization. If not reversed through remineralization, the tooth structure erodes until the demineralized area collapses, resulting in a cavity. (13) A balance of caries-promoting and caries-inhibiting factors is constantly in play (Figure 2).Caries may affect primary or permanent dentition. Caries in the primary teeth of children younger than 6 years is referred to as early childhood caries (ECC). A typical pattern of decay in ECC is that caries first develops on the smooth surfaces of the maxillary primary incisors; ECC may then progress quickly to the remaining primary dentition. This pattern differs from that in the permanent teeth of older children and adults, in whom the occlusal surfaces of molars are most often affected. Older adults may experience caries in crown or root surfaces, which become vulnerable to decay as gum tissue recedes.Caries disproportionately affects certain individuals and groups, predominantly defined by poverty. (1) Exactly how poverty interacts with other variables to produce higher levels of caries is incompletely understood. However, caries risk factors would be expected to cluster within families and communities because resources, habits, cultural and other beliefs, parental role modeling, and dietary and oral hygiene habits are more likely to be shared by family and community members.Child-level characteristics associated with more caries include previous caries, (14) visible plaque, (15) consumption of sweetened liquids and candy, (15)(16)(17) suboptimal fluoride exposure, (18) and infrequent toothbrushing. (19)Caregivers who harbor more cariogenic bacteria, because of untreated caries and/or poor oral hygiene, transmit more bacteria and infect children at younger ages. (16)(20)(21)(22) On the basis of some research evidence, interrupting vertical transmission of cariogenic bacteria is a potential strategy to prevent caries in young children. (23)(24) Other parental factors associated with more caries in their children include multiple decayed teeth, (25) maternal tooth loss from caries, (26) fewer years of maternal education, (23)(27) less than twice-daily toothbrushing, (28) and fatalistic oral health beliefs. (17)Despite many variables associated with increased caries risk, predicting precisely which children are at higher risk for caries before onset of dental decay is a still-evolving science. Because children at high risk for caries develop ECC within the first few years of life, caries risk assessment should ideally take place before first tooth eruption and then be followed by implementation of an appropriate caries prevention program. However, the American Academy of Pediatric Dentistry’s Caries-risk Assessment Tool (29) and other caries risk screening tools rely on a history or presence of caries or predisposing dietary and/or oral health habits. Yet, if caries or habits associated with caries are already present, then it is too late for optimal primary prevention. Low-income status (below 200% of the FPL) is the only caries risk factor that can reasonably be ascertained at first tooth eruption and thus is an appropriate criterion for initial assignment to an intensive caries prevention approach.Fluoride is a ubiquitous mineral. It is found in all soil, bodies of water, plants, and animals and, as such, is a normal constituent of all diets. (30) Early fluoride researchers believed that fluoride achieved its decay-inhibitory effects in a preeruptive fashion, that is, through incorporation into teeth before eruption via a systemic mechanism. Under this assumption, fluoride benefited only young children. On the basis of in vitro, clinical, and epidemiologic evidence, fluoride’s effects are now known to be primarily posteruptive via a topical mechanism. (31)(32) When low levels of fluoride are sustained in saliva (after drinking fluoridated water or brushing with fluoride toothpaste [FTP]), the enamel demineralization and remineralization balance is pushed toward remineralization. Fluoride aids in incorporation of calcium and phosphate into enamel and is itself incorporated into enamel during mineralization. (33) Fluoride-containing enamel, fluoroapatite, is harder and less acid soluble than the original enamel it replaces. Implications of fluoride’s posteruptive mechanism are 2-fold: (1) topical fluoride is more effective than supplements that are swallowed, and (2) fluoride has beneficial effects throughout the lifespan.Excess fluoride intake can result in fluorosis. Dental fluorosis refers to localized changes to tooth enamel, presenting in its mild forms as white markings on the teeth (Figure 3A and B) with more distinct white marking seen in moderate fluorosis (Figure 3C). (34) It is caused by elevated fluoride ingestion during tooth development. (35) Aesthetic considerations for fluorosis are most important in permanent maxillary incisors (the most visible teeth), which are most susceptible to fluorosis before age 2 years. (36)(37)(38)(39) Once permanent teeth mineralization is complete, by 8 years old, there is no longer risk of additional dental fluorosis with further fluoride exposure. (40) It is recommended that fluoride intake in children not exceed 0.05 to 0.07 mg/kg daily. (41) Above this range, an unacceptable degree of fluorosis may result. Below 0.05 mg/kg, fewer children develop fluorosis, but more children develop caries. (42) Early fluoride studies, before community water fluoridation (CWF) or availability of fluoride-containing dental products, established that there is not a single definable level of fluoride intake that maximizes caries prevention without at least some dental fluorosis on a population level. (43) The goal is to limit the degree of fluorosis and number of individuals affected without tipping the balance toward higher caries prevalence. Almost all fluorosis in the United States is very mild or mild (Figure 4); (44) teeth with this degree of fluorosis are more resistant to caries than teeth without fluorosis. More severe dental fluorosis, which manifests as enamel pitting and predisposition to staining (Figure 3D), is unusual in the United States but occurs in other parts of the world where there are naturally high levels of fluoride in the water (eg, >2 ppm). Teeth with severe fluorosis are paradoxically more susceptible to caries.As opposed to the localized effects of dental fluorosis, skeletal fluorosis is a systemic condition caused by long-term exposure to excessively high levels of fluoride—either ingested or inhaled. Chronic fluoride toxicity leads to poor quality bone and painful calcification and ossification of tendons and ligaments. (45) Skeletal fluorosis is extremely rare in the United States (41) but is endemic in parts of India, China, and Africa. (46) When described in the United States, it is typically in individuals who drink large quantities of black tea or very concentrated black tea (black tea naturally contains fluoride). For example, in a 2013 case report in the New England Journal of Medicine, a 47-year-old woman who presented with skeletal fluorosis “reported that for the past 17 years she has habitually consumed a pitcher of tea made from 100 to 150 tea bags daily.” (47) There has not been a reported case of skeletal fluorosis resulting from drinking optimally fluoridated water.CWF is considered among the 10 greatest US public health achievements of the 20th century (48) and one of the few public health interventions with clear-cut, significant cost-effectiveness. (49) CWF refers to the addition of fluoride to that naturally present in water to attain an optimal fluoride level to prevent caries. According to a Centers for Disease Control and Prevention fluoridation census in 2010, 72% of Americans on public water systems receive CWF. (49) The concept of CWF began with observations in the early 20th century that individuals drinking naturally fluoridated water were more resistant to dental decay. (50) Landmark investigations in the 1940s of 21 cities with varying levels of naturally occurring fluoride in the water identified 1 ppm of fluoride in water as the level maximizing caries prevention while minimizing fluorosis risk. (51)(52) Prospective field trials of CWF in 4 pairs of treatment-control cities in the United States and that CWF in a to in caries. In the first US to its public CWF and root caries among adults and has the number of teeth lost to caries in A 2007 a caries preventive for CWF in adults to be (the preventive refers to the in that can be to drinking fluoridated in this there were fewer relative to adults who not drink fluoridated the US of Health and recommended that the optimal fluoride level in US CWF be decreased to This made in of exposure to fluoride other than CWF and an prevalence of dental fluorosis. the fluoride in CWF from to ppm on the that water intake on the CWF ppm in areas and ppm in However, water intake no longer with as as in the and as such, there is now a US of ppm of fluoride in number of CWF to at least of their the New and among fluoridation is not or in many parts of the most of and and in large part because there are not water fluoridation by the Health is (eg, in in more than as a of fluoride for caries prevention. as are often with fluoridated community water, these liquids (41) In a of more than and had a fluoride above in often Americans more and in place of water and these from fluoridated into areas and have become important of dietary (41) This has consumption in areas of with fluoridated water, as as that differences in caries cities with and without in original in the are no longer as CWF in the United States fewer caries in children who drink optimally fluoridated water with who this it more difficult to an fluoride intake for caries or fluorosis to US community water are made by or there have been for and CWF. 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