S. mutans and Lactobacillus are the dominant species.

According to the American Dental Society and American Academy of Pediatric Dentistry, an individual caries risk assessment analysis should be part of a complete dental examination. Disease indicators and risk factors will determine the probability that a specific patient will become susceptible to dental caries, and early intervention therapies may be implemented.

CAMBRA stands for caries management by risk assessment. Using a written form or oral interview, specific elements that could lead to a bacterial imbalance of dental pathogens can be assessed. Dental treatments and restoration recommendations are formulated from this data.

ATP is the basic energy molecule in all living cells. The caries-linked bacteria S. mutans and lactobacilli produce large quantities of acid during sugar metabolism and use ATP to pump this metabolite out of their intracellular space. By assaying the amount of ATP, a correlation can be made to the quantity of bacteria present. By mixing rather simple reagents, a bioluminescence assay for light produced can be correlated with quantities of microorganisms.

Taking an oral swab and placing it in an ampule containing luciferin and luciferase (the firefly enzyme), the following reaction occurs:

The ampule is placed into a sensitive light meter, and the numeric value obtained correlates with the bacterial population, indicating at-risk levels. See www.carifree.com and the CariScreen (Fig. 8-2).

Developed in Sweden, the cariogram is a simple software program that generates a pie graph representation of the elements of a risk assessment survey (Fig. 8-3).

The ICDAS (International Caries and Detection System) has standardized the classification system (www.icdas.org). The GV Black classification system is illustrated in Figure 8-4.

S. mutans and lactobacilli are the most cariogenic, with contributions from Streptococcus sanguis and Streptococcus salivarius. These organisms metabolize sucrose to form acidic byproducts destructive to enamel surfaces. Root surface caries are initiated by Actinomyces viscus on accumulated plaque deposits.

Specifically unique are their ability to survive at low pH and metabolize simple sugars to form acid byproducts. During the process, extracellular polysaccharides are produced, which aid in adhesion within the plaque biofilms.

Fluoride can enter the bacterial cell only as hydrogen fluoride (HF), where it can dissociate and inhibit bacterial enzymes (enolases). As acid production proceeds, some H⁺ and F⁻ ions form HF, which can enter the bacterial cell. At neutral pH, within the bacterial cell, it dissociates, and the fluoride ion is free to act on bacterial enzymes as an inhibitor (Fig. 8-5).

Fluoride present in saliva or plaque fluid will become incorporated into a new crystal surface during remineralization. It competitively displaces OH⁻ ions and then acts topically, from the surface inward, exerting its effects against acid dissolution of the crystal surface. Present in plaque fluid, it will travel into the subsurface enamel with the acids, adsorb to the crystal, and protect it from dissolution. In summary, fluoride present in solution from topical sources enhances remineralization by speeding up the growth of a new surface on the partially demineralized subsurface crystals of the carious lesion. The new crystal surface is fluorapatite-like, with much lower solubility than the original carbonated apatite tooth mineral (Fig. 8-6).

Dental caries occurs when the process of demineralization is faster than the process of remineralization and there is a net loss of tooth mineral into the environment. If the acid production is reduced by removing plaque accumulation or reducing dietary sugar substrates, tooth mineral dissociation will cease (decrease in caries activity [C_A]). The presence of topical fluoride increases enamel resistance to dissolution (forming fluorapatite) and enhances remineralization. It also inhibits bacterial metabolism. Thus, increases in fluoride relate inversely to C_A. Finally, a high salivary buffering capacity decreases caries activity, whereas low flow rates tend to increase C_A.

The enamel and dentin of a tooth are composed of tiny crystals embedded in a protein/lipid matrix. The mineral formed during tooth germination is a highly substituted carbonated apatite. It is related to hydroxyapatite but is more acid soluble, as well as calcium-deficient (replaced by sodium, magnesium, and zinc) and contains 3–6% carbonate replacing phosphate ions in the crystal lattice. During demineralization, carbonate is preferentially lost, and during remineralization, it is excluded and replaced by OH ⁻ or F⁻ ions, thereby decreasing the acid solubility. This is the maturation cycle. Mature enamel is mostly hydroxy or fluorapatite.

The classic experimental measurement of pH changes on tooth enamel surfaces during exposure to fermentable carbohydrates in the presence of acidogenic bacteria (in plaque) over time is called a Stephan plot. It demonstrates the acid production of bacteria (pH decrease) with a glucose swallow, and the gradual rise caused by salivary buffering. At position #3, after left side brushing, the unbrushed side pH drops, whereas the left brushed side #4 remains above the critical pH (Fig. 8-7).

The critical pH for enamel (hydroxyapatite) is 5.3 to 5.5; for fluorapatite, it is 4.5. Carbonated beverages (e.g., Coke, Pepsi) have a pH of about 3.5.

Knowing that the critical pH of enamel demineralization is 5.5, carbonated beverages can be very destructive (Fig. 8-8). The TA (titratable acidity) is the equivalent to titrate to neutral pH. Energy drinks (e.g., Red Bull) and sports drinks (e.g., Gatorade) showed the greatest degree of enamel surface dissolution. Possible explanations for the higher degree of enamel dissolution by sports and energy drinks is the addition of high concentrations of refined carbohydrates (e.g., sucrose, glucose) by the manufacturer, which promotes greater degrees of acid production and, in turn, higher buffering capacities. In addition, beverages containing citric acids have the ability to irreversibly chelate (bind) calcium at higher pH values, with the net effect of an accelerated loss of calcium from tooth structure; this maintains the pH of the beverage below the threshold level (pH = 5.5) for enamel erosion to occur. Red Bull contains sodium citrate (sodium salt of citric acid), a buffering agent that might help in maintaining the pH levels in soft drinks (Fig. 8-9).

The term white spot lesion is applied to the earliest visually observable or macroscopic lesion in enamel. It represents dissolution of the surface structure, with increased porosity, and takes on a dull appearance when air-dried because of the differences in light scattering (refractive index) from the surrounding enamel. These lesions may maintain their surface integrity, become stained and arrested, or progress to frank cavitation lesions.

Enamel caries is primarily an acidogenic or physiochemical progression of tooth mineral dissolution, whereas dentinal caries involves acid decalcification followed by proteolytic or enzymatic degeneration of the organic matrix.

Most early enamel lesions are capable of remineralization, or arresting, if the risk factors are reduced and there is adequate fluoride content in the microenvironment. Risk factor assessment (including diet, bacterial, and salivary analysis), followed by fluoride supplements from topical sources, is thus the first line of therapy.

Proprietary kits from Ivoclar Vivadent and Viadent provide the essential components to culture and grade levels of S. mutans and lactobacilli in saliva and measure salivary pH, flow rates, and buffering capacity. A rapid test by CariFree (www.carifree.com) is a simple, 1-minute chairside bacterial test for assessing patients’ caries risk. CariScreen uses ATP bioluminescence to identify oral bacterial load and has been proven to correlate with patients’ risk for decay. The test is quick and painless. A swab sample of the plaque is taken from the patient’s teeth, which, when combined with special bioluminescence reagents within the swab, creates a reaction that is measured with a meter. The CariScreen will give a score between 0 and 9999 relative light units (RLUs); a score under 1500 RLUs is considering relatively healthy, whereas a score above that shows considerable risk for decay.

Four zones of alternating levels of demineralization illustrate the dynamic nature of caries. The surface zone blocks passage of calcium ions into the body of the lesion. It is well mineralized by replacement ions from plaque and saliva. The body of the lesion is poorly mineralized. The dark zone has some remineralization, whereas the translucent zone has high demineralization (Fig. 8-10).

There are two distinct layers.

A barrier layer of sclerotic (translucent), well-mineralized dentin may be formed by odontoblast deposits into intratubular spaces. Finally, a layer of secondary reactionary-reparative dentin forms at the dentin-pulp junction. These preceding two layers are dependent on a vital pulp’s reaction to noxious stimuli (Fig. 8-11).

Because dentin is a vital tissue, it shows reactivity with bacterial invasion. Caries generally spreads laterally along the dentoenamel junction (DEJ), involving dentinal tubules. At the infected layer of dentin, bacteria enter the dentinal tubules and decalcify the matrix by acid and proteolytic dissociation (microscopic liquefaction foci and clefts are present). The inner affected layer is demineralized, but contains few bacteria. The damage here is reversible if the bacterial metabolism is halted by excavation of the infected layer. Under the affected layer is the sclerotic or microscopic translucent layer, followed by a layer of reparative or reactionary dentin produced by odontoblasts at the dentopulpal boundary.

Carious dentin fills most of the slide, on the right. At the far left is the pulp; the faint blue dots are lymphocytes (chronic inflammation). To its right is a band of reparative dentin that protected the pulp from infection for a time. Next, progressing right, is a thin band of sclerotic dentin, followed by a layer of affected dentin, and at the far right is infected dentin.

Note that zones of destruction coalesce to form clefts and liquefaction foci. These are filled with necrotic debris. These advancing bacteria seem to have acidogenic and proteolytic properties, resulting in the enzymatic destruction of the organic dentin matrix. Horizontal clefting is typical of dentinal caries. The process of beading, coalescence, and clefting typifies progression of dental caries.

All infected dentin must be removed for successful tooth viability. Because affected dentin has undergone only early demineralization, removal may not be necessary. Topical bonded dentin sealants containing fluoride affect a barrier under restorations.

Because smooth surface caries (interproximal or cervical) have a wide enamel surface pattern that converges with the anatomic form of the enamel rods toward the DEJ, fewer dentinal tubule are affected, enamel undermining is generally less, and the rate of progression is slow. These lesions have a high success of remineralization with adequate fluoride exposure and reduction in risk factors.

Pit and fissure caries are narrow at the enamel surface and spread widely as the caries progresses to the DEJ, involving many dentin tubules and creating extensive undermining. The progression is often more rapid than that of smooth surface caries. Because of the anatomic sheltering of bacterial plaque, remineralization is not easy, and fissurotomy followed by sealants is necessary for early lesions.

See Figure 8-15 for an example of a decision tree for the management of pit and fissure tooth surfaces.

Caries may be detected by a combination of techniques. The most commonly accepted criteria for identifying infected tooth structure are the following: (1) discolored, softened tooth structure; (2) frank cavitation; and (3) areas of radiolucency on radiographs. Direct visual inspection of pits and fissures, root surfaces, and interfaces of restorations and tooth with a sharp explorer and air-drying with the use of magnification are the first steps of the examination. This procedure is supplemented by evaluating properly angulated bitewing and periapical radiographs. Finally, the use of transillumination from a visible light curing wand can reveal shadowing and discoloration on occlusal and interproximal tooth surfaces.

Note: This step may be resequenced in the apprehensive patient until full trust and compliance are achieved because extractions may be too traumatic as an initial treatment phase.

Caries detector solutions are usually a colored dye (red, green, blue) in a propylene glycol base; they help distinguish between infected and affected dentin. The dye bonds to the denatured collagen in the infected dentin that is part of the decay process. The affected dentin, which may be slightly softer than sound dentin, is not infused with bacteria and is not stained, but still may show a dye-stained haze (pink haze with red dye). This dentin should not be removed. The caries detector solution is applied for 10 seconds and then rinsed off. Any deeply stained tooth structure is then removed. The materials also help identify cracks in tooth structure (e.g., Seek [Ultradent], Snoop [Pulpdent]).

Note: Some products may decrease the bond strength to dentin and careful consideration of their use is necessary when high bonding requirements are needed.

Some current thought reflects the goal of cleaning a preparation before bonding or placing a restoration with the addition of a bactericidal agent to reduce sensitivity and bacterial growth under a restoration. It is thought that bacteria reaching the pulp may contribute to sensitivity. Current products contain benzalkonium chloride and EDTA or 2% chlorhexidine gluconate.

Acidulated fluoride (APF) solutions and topical 0.4% stannous gels (Gel-Kam, Colgate) remove the glaze from porcelain, glass ionomer, and composite restorations. It is best to use neutral pH supplements if these restorations are present. Always check the product specifications.

The medical model attempts to shift the caries balance toward no caries by using medical and behavioral components. The key elements are:

BASF, in collaboration with the Berlin-based OrganoBalance GmbH, will commercialize Pro-t-action, made from probiotic microorganisms (Lactobacillus spp.). The active ingredient in Pro-t-action binds to and eliminates caries-causing bacteria (S. mutans) from the mouth. A particular strain of L. paracasei has been identified, and BASF developed a proprietary production process so that the active ingredient can easily be integrated into common consumer products used for daily oral care such as toothpaste, mouthwash, candies, lozenges, and chewing gums. By swishing and swallowing or rinsing, the clumped pathogens are easily expectorated from the mouth. This is the first pathogen-specific clearance rinse. See http://www.basf.com/group/corporate /en_GB/innovations/research/innovation/innovative-solutions/pro-t-action.

As noted earlier, in questions 8 and 9, CAMBRA is a modern caries treatment concept that attempts to identify pathologic and risk factors and implements protective strategies that can prevent cavitation or progression of carious lesions. Clinicians identify the patient’s caries risk by evaluating disease indicators, risk factors, and preventive efforts. After evaluation, a caries risk classification can be determined, and preventive chemical measures and lifestyle and habit changes can be suggested and implemented by the clinician.

Caries may be detected by a combination of techniques. The most commonly accepted criteria for identifying infected tooth structure are the following: (1) discolored softened tooth structure; (2) frank cavitation; and (3) areas of radiolucency on radiographs. Direct visual inspection of pits and fissures, root surfaces, and interfaces of restorations and tooth, along with additional tactile information from a sharp explorer and air-drying with the use of magnification, are the first steps of examination. This procedure is supplemented by evaluating properly angulated radiographs. Finally, laser fluorescence and fiberoptic devices can be used in diagnosing carious lesions.

Studies have focused on anticaries vaccines for S. mutans. These vaccines have antibodies against bacteria surface receptors Ag I and II, preventing microorganism adhesion to tooth structure. Newer investigations have targeted intranasally administered anticaries DNA vaccines to produce mucosal and systemic responses and protection against caries.

Patients who exhibit high caries incidence, root caries, or cervical caries and who might fit into one or more of the following groups:

Attrition is the physiologic wear of tooth structure resulting from normal tooth to tooth contact over time.

Erosion is the loss of tooth structure by a chemical process that does not involve bacterial action. It is generally caused by the consumption of foods that contain phosphoric or citric acid, such as fruits, fruit juices, and carbonated or acidic beverages. Excessive exposure to gastric acids because of vomiting is also a contributing factor.

Abfraction is defined as the pathologic loss of tooth substance caused by biomechanical loading forces. The loss of structure is usually seen as wedge-shaped cervical lesions at the cementoenamel junction (CEJ) that may not be carious. This theory is used as an alternative explanation for areas that historically were attributed to toothbrush abrasion. They are also referred to as noncarious cervical lesions (NCCLs).

The classic cavity preparations, according to Black’s principles, are generally not needed for contemporary bonded retained composite and amalgam restorations. Dovetails, retention grooves, and extension into uninvolved occlusal grooves are generally not needed. Maximizing tooth structure dominates design, with sealants replacing groove extensions.

The Black approach to operative dentistry tends toward the destruction of healthy tooth structure to remove smaller amounts of unhealthy tooth structure (extension for prevention). The concept of microdentistry seeks to diagnose unsound tooth structure that is a threat to the tooth and remove that threat, with minimal encroachment on the surrounding healthy tooth structure.

A fissurotomy involves the conservative preparation of occlusal pits and fissures using air abrasion or special burs designed for this purpose; the fissurotomy kit (Ivoclar Vivadent) is one example. This procedure is used to treat pits and fissures with incipient decay. Preparations are typically narrow, long, and irregularly deep, so they are often restored with flowable composites. Hybrid composites, although stronger and more wear-resistant than flowables, may be clinically more difficult to place into such preparations without the incorporation of voids.

It is often difficult to determine caries activity in pits and fissures, particularly with conventional means. Concerns arise about the placement of sealants over undiagnosed caries. Questionable occlusal grooves covered with a sealant, particularly in fluoridated communities, may mask more extensive subsurface caries activity. The fissurotomy offers better access and is a conservative technique for maximizing the retention of healthy tooth structure while ensuring certain removal of all decay.

The tunnel preparation is a conservative approach to restoring class II caries in teeth with relatively small interproximal lesions. It conserves the proximal marginal enamel by using only occlusal, buccal, or lingual access and then angulating mesially or distally until the external tooth enamel is perforated. Usually, application of a matrix band beforehand protects the adjacent tooth wall. The tooth cavity is then packed from the access dimension.

Any narrow access to reach interproximal caries can be called a slot preparation. The access may be buccal or lingual, as in a class III lesion, or from the occlusal aspect. The ideal is to conserve tooth structure by removing only caries and a minimal amount of tooth structure.

This technique uses pressurized delivery of an abrasive powder (e.g., aluminum oxide) to prepare teeth for restoration. The claimed advantages are less trauma and a less invasive, heatless procedure, often not requiring local anesthesia. It is ideally suited for pit and fissure sealant preparations and conservative class I and V preparations using flowable composites. Disadvantages include the need for special high- speed evacuation equipment and high cost of the units.

Air abrasion is based on kinetic energy. Abrasive particles, typically 27- to 50-μm aluminum oxide, are propelled at high velocity to remove tooth structure. By varying the speed of the particles, the length of time to remove tooth structure and often the level of sensitivity can be controlled.

Depending on the type of unit and manufacturer, the propellant can range from compressed air or nitrogen to operatory-compressed air lines or units with built-in air compressors.

All classes of cavity preparation may be performed with air abrasion. Some operators may use a high-speed hand piece to gain initial access to deep grooves, pits, marginal ridges, and hard-to-reach areas. Although air abrasion units have the ability to remove dental amalgam, some questions remain about the amount of mercury released by air abrasion versus removal with conventional, high-speed hand pieces.

Treatment goals of microdentistry include preservation of sound occlusal enamel with minimally invasive occlusal preparations and the use of tunnel or slot preparations to treat primary interproximal caries. Air abrasion is much more selective in the structure it cuts, thereby removing very little sound tooth structure relative to the use of high-speed hand pieces. Additionally, the vibration from high-speed hand pieces can cause enamel fractures that air abrasion cannot (Table 8-1).