Chapter 374. Dental Caries

Epidemiology

Dental caries, more commonly known as tooth decay or cavities, is an infectious, transmissible, diet-mediated oral disease that is largely preventable. It is the most common chronic disease among US children—being 5 times more common than asthma and 7 times more common than hay fever.1Despite a decline in dental caries among the population as a whole, this decline has not translated to all age groups, and profound disparities exist among certain populations.2 The Centers for Disease Control and Prevention reported that among children surveyed during the years 1999 to 2002, 28% of 2- to 5-year-old children (representing approximately 4 million US children) have visually evident cavities. Prevalence is apparently trending upward from the 1988 to 1994 estimation that 24% of young children have caries.2 Approximately 80% of dental decay is concentrated in 25% of children.1 In the United States, children of racial and ethnic minorities or low-income families experience the worst oral health, are at the highest risk, and are less likely to obtain timely care compared to their higher-income, non-Hispanic white counterparts.1 Pediatriciansand other primary care professionals are in an ideal position to target these high-risk populations, as children may see their pediatrician for preventive visits up to 10 times before 2 years of age.

Pathophysiology

As dental caries is a disease process that may be established in infancy, understanding the pathophysiology of dental caries enables the pediatrician to conduct a dental caries risk assessment; provide anticipatory guidance and preventive counseling; and, in collaboration with their dental colleagues, ensure the establishment of a dental home by age 1, or as soon as possible. The concept of a dental home is derived from the American Academy of Pediatrics’ definition of a medical home. The dental home is the ongoing relationship between the dentist and the patient, inclusive of all aspects of oral health care delivered in a comprehensive, continuously accessible, coordinated, and family-centered way.3 Dental caries is the pathological disease process that leads to the loss of tooth mineral and eventually cavitation of the tooth surface (“cavity”). The etiology of dental caries is multifactorial. The primary components required for dental caries activity to become established are one or more susceptible tooth surfaces, cariogenic (decay-causing) bacteria, fermentable carbohydrates (particularly sucrose), and time.

Demineralization/Remineralization

Dental caries results from an overgrowth of specific oral bacteria that are present in dental plaque (the sticky white or yellow “biofilm” that forms on the tooth surface). The cariogenic bacteria are acidogenic, which means they produce acids by metabolizing fermentable carbohydrates. These acids lead to the loss of minerals (demineralization) such as calcium, phosphate, and carbonate from the tooth. The first sign of demineralization is a thin white line along the gingival margin (Fig. 374-1). At this initial stage, the caries process is reversible through the process of remineralization. During remineralization, there is an uptake of calcium and phosphate from the saliva into the tooth enamel, which is facilitated by the presence of fluoride. Fluoride becomes incorporated into the remineralized enamel as fluorapatite, which renders the teeth more resistant to future acidic challenges. If demineralization is not stopped or reversed, the caries process continues and the result is tooth cavitation (Fig. 374-1).

A cavity, or hole in the tooth, is actually a very late stage in the dental caries process. Thus, dental caries is a dynamic process, and under normal conditions, there is a balance between demineralization and remineralization. John Featherstone originally described this as the Caries Balance model in which pathological factors (which cause demineralization) battle protective factors (which enhance remineralization).4 Pathological factors include cariogenic bacteria, altered salivary flow or function, and poor dietary habits (ie, frequent ingestion of fermentable carbohydrates). Protective factors include salivary flow and components, antibacterials, and fluoride.

It is well accepted that Streptococcus mutans (SM) are the primary microbiological organisms associated with the initiation and progression of dental caries. Early clinical investigations on the microbiology of dental caries indicated that MS could not be detected in the mouth of predentate infants, thus suggesting that a nonshedding oral surface was needed for colonization.5,6 More recent research demonstrates that MS can be isolated from the tongue7and oral developmental nodules (Bohn’s nodules) of infants as early as 3 months of age,8 thus contradicting earlier reports that MS requires a nondesquamating surface for colonization. The bacteria can metabolize any fermentable carbohydrate. Sucrose is considered to be the most cariogenic carbohydrate.1 However, glucose, fructose, and cooked starches are also metabolized by plaque bacteria to produce acid.

Early childhood caries (ECC), previously termed nursing caries or baby-bottle tooth decay, is a particularly virulent form of tooth decay that affects the primary teeth of infants and preschool children. Typically, decay begins on the maxillary incisors and then spreads to the maxillary and mandibular molars. The severity of ECC is based on the child’s age, the number of teeth affected, and the tooth surface involved. ECC is considered severe if there is any sign of smooth-surface decay in a child younger than 3 years of age.9 Studies demonstrate that children with early childhood caries have MS counts that exceed 30% of the cultivable plaque flora.10-12

Conversely, in children with negligible to no caries activity, MS comprises less than 1% of total cultivable flora.13 SM may be acquired through vertical or horizontal transmission. Vertical transmission is the spread of bacteria via saliva from the primary caregiver to the child. The mother’s saliva is the main reservoir from which infants acquire SM.5 Successful transmission and colonization depends on several factors, including a minimum infective dose,14 the size of the inoculum,15 and the frequency of the inoculation.13 Horizontal transmission is the spread of bacteria between members of a group5 (eg, among children in daycare). The timing of SM transmission is important, as acquiring SM before 2 years of age is a significant risk factor for developing ECC and future dental caries.5

Children with early childhood caries are more likely to experience future decay in both their primary and permanent teeth.16 The consequences of dental caries go beyond teeth. Dental caries can affect overall quality of life, such as insufficient height and weight, interference with learning and restriction of activity, and missed days from school.1 Pain associated with dental caries can interfere with eating and sleeping.1 Decay that progresses to the pulp causes intense pain and pulpal necrosis, and may result in a dental infection or abscess that may become life-threatening (see Chapter 375). When children present with a severe dental abscess, treatment may require hospital admission with an IV course of antibiotics and extraction of the offending tooth. Due to the age and cooperative ability of the child, treatment may need to be rendered under general anesthesia, thus increasing the cost and morbidity.

Dental caries may be controlled by enhancing patient protective factors and suppressing their pathological factors. Although understanding the underlying risk factors for dental caries will not completely eliminate the risk factors in most cases, it will allow for an enhanced balance between the risk factors and protective factors.17

Caries Risk Assessment

Although the incidence of dental caries is very high in children, the majority of decay is concentrated in a small percentage of them. It would be more efficacious and cost effective to focus strategies on preventing and managing dental caries based on risk rather than treating all patients in the same manner. Risk factors are not constant, and an individual’s risk of caries changes with time. Risk factors for caries may be physical, biological, behavioral, or lifestyle-related. Table 374-1 provides examples of factors that are associated with an increase in caries risk for children.18

In children, the best predictors of caries in primary teeth are a past history of caries experience, followed by parents’ education and socioeconomic status.19 Family history of caries, particularly in the mother, is also an important predictor of caries in children.20 Children who have low birth weight or who are premature may require a special diet or may have developmental enamel defects or disabilities that increase their caries risk. Many studies have found that sugars are the most important factor in caries development. Caries risk is greater if sugars are consumed at high frequency and are in a sticky and retentive form (eg, raisins and granola bars) that remain in the mouth for longer periods of time.21 Again, sucrose is the most cariogenic, but mixtures of heat-treated starch and sucrose are also cariogenic.22

The American Academy of Pediatrics recommends that every child begin to receive oral health risk assessments by 6 months of age by a qualified pediatric health care professional. Children who belong to high-risk groups should be referred to a dentist by 12 months of age to establish a dental home.23

Nutritional Counseling

Dental caries is a diet-mediated disease, with dietary sugars being an important part of the process of caries development and progression.20 Juice and sugar-sweetened beverage consumption has been linked to caries development.24,25 Sucrose, glucose, and fructose contained in fruit juices are easily metabolized by oral bacteria to form acids that slowly dissolve teeth. Bottles and sippy cups containing juice, milk, or any fermentable carbohydrate allow frequent or prolonged consumption, which increases the risk for early childhood caries.

Human milk by itself does not promote caries.26 However, case reports suggest that after the eruption of the first primary teeth, infants may be at increased risk for caries if they breast-feed on demand or throughout the night. They are also at increased risk if they receive sugary liquids in a bottle or are nursing and eating foods with sugars and fermentable carbohydrates.

Parents and caregivers should receive counseling on the importance of reducing high-frequency or prolonged exposures to obvious and hidden sugars in foods and drinks. Cariogenic foods, including sugary foods and drinks, should be limited to meal times. Sugary drinks, including fruit juice, should be avoided in nursing bottles or sippy cups. Children should be discouraged from taking a bottle or sippy cup with milk or juice to bed. During sleep, the flow of saliva is decreased, resulting in reduced clearance of the sugary liquid from the oral cavity.

Oral Hygiene

Oral hygiene should begin prior to the emergence of the first tooth. When possible, a dental home should be established for a child by the first birthday. During this first visit, an oral exam is performed, a child’s risk and protective factors are identified, and preventive counseling is given regarding cleaning of the mouth, toothbrushing, flossing, and using toothpaste.

Mechanical removal and dislocation of plaque accumulations, through simple tooth brushing, is one of the most effective preventive measures that can reduce the risk of caries. In very young children, the presence of plaque on the labial or facial surfaces of maxillary primary incisors is the best predictor of future development of early childhood caries.27

Since the quality of cleaning is most important, young children require assistance with toothbrushing from an adult caregiver. Toothbrushing in young children is a simple and fast procedure, although resistance and a lack of cooperation are normal reactions to oral hygiene measures in infants, toddlers, and preschoolers. With correct positioning (such as using a knee-to-knee position with two adults or having the adult approach brushing from behind the child’s head) and retraction of the lips and cheeks, it should take no more than 1 minute to brush a young child’s teeth (Fig. 374-2).

Older children who have adequate manual dexterity (typically by 6 to 8 years of age) may require only parental supervision. Flossing is required when teeth develop contacts (usually after 3 to 4 years of age for posterior teeth) and proximal surfaces cannot be reached with a brush. Brushing and flossing before bedtime is of paramount importance, as caries activity is higher at nighttime, when salivary flow decreases. Brushing more frequently with fluoride toothpaste can provide added protection from caries. The practice of brushing twice a day has become a social norm that is convenient for most daily routines, and it is the basic tenet for preventing caries.28

Use of Fluorides

Use of fluorides is the most effective way to prevent caries.28 In the ongoing dynamic between demineralization and remineralization at the enamel surface of teeth, fluoride demonstrates its greatest effects through topical mechanisms by promoting remineralization and inhibiting bacterial metabolism. Therefore, therapeutic use of fluoride for children should focus on maximizing topical contact and using lower dose, higher frequency approaches.29

Water fluoridation is considered the most cost effective, most convenient, and most reliable method of providing optimal fluoride benefits, because it does not depend on individual compliance. Caries rate decreases of 18% to 40% are now attributable to water fluoridation.2 For children who do not have access to optimally fluoridated drinking water, systemically administered fluoride supplements are recommended.

The most recent recommendations for fluoride supplementation (Table 374-2)—approved in 1994 by the American Dental Association, the American Academy of Pediatrics, and the American Academy of Pediatric Dentistry—emphasize initial supplementation at 6 months of age and continuing to age 16. This supplementation schedule was developed with the intention of minimizing fluorosis while maximizing the topical cariostatic effects after teeth erupt. This schedule assumes the regular use of fluoridated toothpaste.

Before recommending fluoride supplementation, the fluoride content of water, whether it be well water or bottled water, should be tested. Testing of private wells is available through local and state public health departments and through some private laboratories. If the fluoride concentration is not listed on the label of bottled water, the bottler can be contacted directly to obtain this information. If multiple water sources are used, determining the total fluoride exposure becomes difficult. Instead of purchasing bottled water, filtering tap water may be considered. However, some reverse osmosis systems do not allow fluoride to pass through.

For self-administered care, fluoride toothpaste is the most powerful intervention for caries prevention, because it has high clinical effectiveness and social acceptability.30 The current perspective is that regardless of caries risk, all age groups should use commercially available fluoridated toothpaste at least two times per day.31 To minimize the risk of fluorosis, children younger than 2 years of age should limit the amount to a small smear applied onto a soft toothbrush by an adult caregiver, while older preschoolers may use a pea-size amount.32

Children who are at increased risk for caries may be prescribed topical fluoride in the form of gels or rinses to be used at home. For example, in high caries–risk children who are able to rinse and expectorate, 0.2% or 0.05% sodium fluoride rinse may be used. Additionally, professional applications of fluoride treatment every 6 months or more may also be recommended. These may be in the form of gels, foam, and varnishes. Fluoride varnish is a sticky substance that is easily applied onto the teeth and hardens quickly on contact with saliva. Fluoride varnish is well accepted by young children.

Delaying the Transmission of Streptococcus Mutans

Early acquisition of Streptococcus mutans (SM) is a major risk factor for early childhood caries and future caries experience. Preventing and delaying the acquisition and transmission of SM involves reducing the bacteria in the mother, siblings, and other caregivers; altering saliva-sharing activities; brushing two times per day with fluoride toothpaste; avoiding caries-promoting feeding behaviors; and having an oral health evaluation by a dental professional by the first birthday.5

Sealants

The pits and fissures on the chewing surfaces of teeth are the most susceptible to caries. A sealant is a plastic material that is usually applied to the chewing surfaces of the posterior teeth, molars, and premolars. This plastic resin bonds into the depressions and grooves (pits and fissures) of the chewing surfaces of back teeth. The sealant acts as a barrier, protecting enamel from plaque and acids. Both primary and permanent teeth that are judged at risk for caries would benefit from sealants.33

Xylitol and Antimicrobials

Xylitol is a sugar substitute that is part of the polyol family and includes sorbitol, mannitol, and maltitol. It is produced from birch trees and other hardwood trees containing xylan. It is approved by the FDA and safe to use in children. Sugar alcohols have been shown to be noncariogenic, and xylitol exhibits protective effects from dental caries. Studies indicate that xylitol can reduce Streptococcus mutans (SM) in plaque and saliva, which can reduce dental caries in young children and their mothers and can decrease the vertical transmission of SM from mother to child.34

Xylitol use is attractive, because, as a sugar substitute, it can reduce the overall consumption of other sugars in the diet. Xylitol is commonly available in chewing gum; however, a range of 6 to 10 grams divided into at least three consumption periods per day is necessary for xylitol to be effective with chewing gum as the delivery system.34 Unfortunately, chewing gum is not a suitable product for toddlers and preschoolers, and presently there is no safe xylitol substitute available for this age group.34

Antimicrobial rinses can reduce the number of cariogenic bacteria and can be useful in high caries–risk individuals. Presently, the most effective antibacterial rinse is 0.12% chlorhexidine gluconate. To avoid the possibility of swallowing, these rinses are recommended only for children who can spit and rinse.4

Although repairing damaged tooth structure does improve stability and function, it does not address the underlying disease process.34Instead, a comprehensive approach to disease management that is modeled on the medical management of chronic conditions must focus on removing cariogenic bacteria and promoting tooth remineralization, along with repairing damaged tooth structure.36

Young children who are apprehensive or uncooperative and children with special health care needs may require nitrous oxygen/oxygen analgesia, conscious sedation, or general anesthesia as adjunctive care to the surgical dental treatment (see Chapter 380).