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Profile in Oral Health Trisha E. O'Hehir, RDH, BS Editorial Director, Hygienetown Magazine

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by Trisha E. O'Hehir, RDH, BS
Editorial Director, Hygienetown Magazine

Most people think of caries or tooth decay as just the hole in the tooth and not the entire process that leads up to the break in enamel. The traditional approach to the treatment of caries is being expanded to include the bacterial infection as well as the repair. By far, the most common approach and indeed the traditional approach to caries is that of repairing the damage done to teeth by the caries process. Drilling with burs or laser treatment eliminates the damaged tooth structure and then a restorative material is used to replace the lost structure.

This is the way dentists have been educated for centuries. The majority of their training is devoted to repairing tooth surfaces ravaged by tooth decay. Traditionally, very little time was spent on the bacterial infection responsible for the resulting tooth surface lesions. Tooth decay was thought to be inevitable and so repair was the only approach needed and took priority over prevention and reversal of the dynamic demineralization/remineralization process.

The old repair philosophy for dental caries is being expanded, based on mounting scientific evidence of caries as an infectious disease that can be prevented and that early stages can actually be reversed, thus avoiding a break in tooth enamel. This new philosophy encompasses much more than repair. It begins with strategies to control bacterial transmission from parent to child; new tools for evaluation of saliva and bacteria; technologies for measuring tooth surface demineralization and remineralization; products and treatments for remineralization; the healthy sugar, xylitol, to reduce oral bacterial accumulation and enhance remineralization; and risk assessment strategies. The acronym given to this expanded philosophy is CAMBRA or caries management by risk assessment.

What Is Caries?
According to Dr. John Featherstone, caries or dental decay is the most common chronic childhood disease in the U.S. today, bumping asthma out of first place. Eight percent of one-year-olds have already experienced tooth decay. With each year, the figure nearly doubles: two-year-olds – 22 percent; three-year-olds – 35 percent; and four-year-olds – 67 percent. Because dental decay is not usually life threatening, it isn't considered significant in the overall picture of human health. However the economic effects are staggering and unnecessary pain is suffered by those experiencing dental decay.

Caries is much more than a hole in the tooth. It is an infectious disease caused by acid producing (acidogenic) bacteria that prefer to live in an acid environment (aciduic), primarily Mutans streptococci (MS) and Lactobacilli (Lb), that are spread vertically from parent to child. The bacteria convert fermentable carbohydrates into acid that penetrates the crystal surface of carbonated hydroxyapatite of enamel, beginning the demineralization process below the tooth surface. This is an important distinction, because the subsurface demineralization takes place before a break in enamel happens, allowing for reversal of the caries process with remineralization.

Caries begins at the atomic level as a molecule of organic acid diffuses through the enamel to the crystal surface of carbonated hydroxyapatite. Loss of calcium, phosphate, and carbonate occurs from specific sites in the crystal. Reversal of demineralization also occurs at the atomic level as calcium, phosphate, and fluoride combine to build a new surface. This is a continuous process, starting at the atomic level within the enamel, and progressing deeper and deeper into the tooth. For root caries, the process begins in the cementum and eventually moves into the dentin.

Remineralization occurs when the saliva neutralizes the acid and salivary minerals are redeposited into the enamel surface. Demineralization/remineralization is a dynamic process that happens several times each day and can occur in dentin and cementum as well as enamel. This dynamic process begins as soon as the teeth erupt.

In 1984, Dr. Walter Loesche published a frequently referenced study defining in great detail the role of MS in the dental decay process. He concluded that treatment strategies that interfered with bacterial colonization of MS may have a profound effect on the incidence of dental decay.

Babies are born essentially germ-free with no MS in their mouths since oral epithelium is not an adequate surface for bacterial colonization. In 1993, Dr. Page Caufield identified a discrete window of infectivity between 19 and 31 months, during which bacteria from the mother are transmitted to the baby. This occurs when the teeth first erupt, as MS requires a non-sloughing surface for colonization. Mothers with high levels of MS serve as an important source of infection during this period and need to be considered when intervention is planned. Transmission of MS from parent to child is termed vertical transmission. Horizontal transmission also occurs between the infant and nurseries, daycare facilities and other family members.

Caries Interventions
Dealing with an ongoing infectious process allows for intervention at different stages along the way. The first deals with the bacteria and prevention of vertical bacterial transmission from parent to child. Second, diet counseling to control the intake of fermentable carbohydrates. Third, detection methods are now available to determine salivary bacterial levels as well as identification of bacterial species found in the mouth. Fourth, both mechanical and chemical methods are used to reduce bacterial levels in the mouth. Fifth, lasers like the DIAGNOdent are used to measure both demineralization and remineralization of tooth surfaces. Sixth, fluoride, calcium, phosphate and xylitol are key ingredients used topically to prevent bacteria from producing acids and to enhance the remineralization of enamel and cementum.

Dentistry advocates the use of risk-assessment tools to determine the need and type of treatment that should be provided. Risk assessment is applied to all ages, from birth to adult, taking into consideration past decay experience; exposure to fluoride, xylitol, and products that contain Recaldent (CPP-ACP), NovaMin or ACP; dietary habits; salivary levels, dental conditions such as orthodontic appliances or exposed roots; visible plaque biofilm; and deep pits and fissures to name a few.

Vertical Transmission of Oral Bacteria
In 2000, Dr. Eva Söderling showed that chewing 100 percent xylitol-sweetened gum four times a day, for a daily total of six to seven grams of xylitol, was more effective in reducing the transmission of MS from mother to child than fluoride varnish applications or chlorhexidine varnish applications. Use of xylitol chewing gum began when the children were three months old and continued until they were two years old. When the children were five years old, those whose mothers had chewed the xylitol gum needed 70 percent less restorative treatment than the two varnish groups. This long-term effect was evident despite the fact that mothers no longer chewed xylitol gum after the children were two years old.
Destructive Factors: Protective Factors:
· Acidogenic/aciduric bacteria
· Fermentable carbohydrates
· Acid production
· Low pH levels
· Xerostomia		 · Saliva to neutralize acids
· Saliva to raise the pH
· Salivary immunoglobins to fight the
  bacteria
· Salivary minerals to remineralize
  tooth surfaces
· Fluoride to enhance
  remineralization
· Fluoride for antibacterial effects
 · Xylitol to alter and wash away
  acidogenic bacteria
· Xylitol to stimulate salivary flow
· Xylitol to raise the pH
· Xylitol to enhance remineralization
· Calcium to enhance
  remineralization
· Phosphate to enhance
  remineralization
Caries Prevention
In 2005, Dr. John Featherstone published a randomized, clinical trial demonstrating that restoring teeth alone did not eliminate the bacteria causing the disease and did not reduce future decay rates. Also in 2005, Dr. George Stookey published an extensive review of the literature arguing against the use of sharp explorers for caries detection. Sharp explorers not only break through demineralized enamel that could be remineralized, thus preventing cavitation, but they also transport infectious bacteria from infected tooth sites to healthy tooth sites.

In 1945, water fluoridation began in Grand Rapids, Michigan. The preventive benefits of fluoride had already been discussed in Europe during the 19th century. In 1909, Dr. Frederick McKay observed stained, mottled and even cracked teeth in 90 percent of children in the Pike's Peak region of Colorado. This was later determined to be fluorosis, due to excessive levels of fluoride in the water. Studies determined that very low levels of 1.0 part per million actually prevented tooth decay by establishing harder enamel before the teeth erupted. Systemic fluoride is released in the saliva, thus bathing the teeth and promoting remineralization. Water fluoridation is reported to reduce caries 20 to 60 percent, depending on the age group.

Fluoride is available in both systemic and topical forms in water, tablets, lozenges, toothpastes, rinses, and professional applications. Researchers suggest that the varnish is the most effective topical form of fluoride. Varnishes were developed in the 1960s, contain five percent sodium fluoride and are reported to reduce caries rates by 25 to 45 percent.

In 1995, the classic xylitol study was published, which demonstrated that, in children who chewed 100 percent sweetened xylitol gum, the infectious carious process stopped. Baseline decayed, missing or filled surfaces (DMFS) scores among fourth graders in Belize were approximately 5. After 40 months, the rate in the xylitol group was 4, the control group with no gum, 9, and the sugar gum group 11. Many other studies have confirmed these findings, showing that chewing gum sweetened with 100 percent xylitol will reduce MS and Lb levels in saliva and therefore the incidence of cavitated lesions.

Remineralization Strategies
Putting minerals back into the tooth hardens the surface and prevents cavitation. Calcium, phosphate and fluoride can remineralize tooth surfaces. Several products using calcium, phosphate and fluoride are now available: Recaldent, amorphous calcium phosphate (ACP), SensiStat and NovaMin. Also, products that stimulate saliva will raise the pH and allow the saliva to deposit minerals into the tooth structure. Remineralization products are used both in professional applications and home use products.

Conclusion
Scientific evidence is mounting and can no longer be ignored. Caries is an infectious disease, transmitted from parent to child that can be prevented and even reversed before the acid causes cavitation of the enamel, requiring traditional restorative repair. Tooth decay was never just a hole in the tooth that needed to be repaired. It's a complex process with many opportunities for hygienists to intervene with strategies for prevention and reversal of the tooth decay process.
Terminology
The singular term "caries" is used to describe many
steps and stages in the process of this infectious disease.
· Active lesion
· Affected dentin
· Arrested lesion
· Brown spot lesion
· Carious lesion
· Cavitation
· Demineralization
· Dental decay
· Dentinal caries
· Early childhood caries		 · Enamel caries
· Histologic caries
· Infected dentin
· Pit and fissure lesion
· Radiographic lesion
· Root caries
· Secondary caries
· Smooth surface lesion
· Stain
· White spot lesion		 Caries-related Acronyms
ACP - Amorphous Calcium Phosphate
CAMBRA - Caries Management by Risk Assessment
CPP - Casein Phosphopeptides
MID - Minimally Invasive Dentistry
WCMID - World Congress of Minimally Invasive Dentistry
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