Tooth decay, also known as caries or cavities, is an oral disease that affects many people. Unlike other diseases, however, caries is not life-threatening and is highly preventable, though it affects most people to some degree during their lifetime.
Natural bacteria live in your mouth and form plaque. The plaque interacts with deposits left on your teeth from sugary and starchy foods and produces acids. These acids damage tooth enamel over time by dissolving, or demineralizing enamel, which weakens the teeth and leads to tooth decay.
Dental caries (Latin, "rot"), also known as tooth decay or a cavity, is an infection, bacterial in origin, that causes demineralization and destruction of the hard tissues of the teeth (enamel, dentin and cementum). It is a result of the production of acid by bacterial fermentation of food debris accumulated on the tooth surface.If demineralization exceeds saliva and other remineralization factors such as from calcium and fluoridated toothpastes, these once hard tissues progressively break down, producing dental caries (cavities or carious lesions, that is, holes in the teeth). Today, caries remains one of the most common diseases throughout the world. Cariology is the study of dental caries.
Depending on the extent of tooth destruction, various treatments can be used to restore teeth to proper form, function, and aesthetics, but there is no known method to regenerate large amounts of tooth structure. Instead, dental health organizations advocate preventive and prophylactic measures, such as regular oral hygiene and dietary modifications, to avoid dental caries.
Montage of four pictures: three photographs and one radiograph of the same tooth.
(A) A small spot of decay visible on the surface of a tooth.
(B) The radiograph reveals an extensive region of demineralization within the dentin .
(C) A hole is discovered on the side of the tooth at the beginning of decay removal.
(D) All decay removed.
A person experiencing caries may not be aware of the disease.The earliest sign of a new carious lesion is the appearance of a chalky white spot on the surface of the tooth, indicating an area of demineralization of enamel. This is referred to as a white spot lesion, an incipient carious lesion or a "microcavity". As the lesion continues to demineralize, it can turn brown but will eventually turn into a cavitation ("cavity"). Before the cavity forms, the process is reversible, but once a cavity forms, the lost tooth structure cannot be regenerated. A lesion that appears dark brown and shiny suggests dental caries were once present but the demineralization process has stopped, leaving a stain. Active decay is lighter in color and dull in appearance.
As the enamel and dentin are destroyed, the cavity becomes more noticeable. The affected areas of the tooth change color and become soft to the touch. Once the decay passes through enamel, the dentinal tubules, which have passages to the nerve of the tooth, become exposed, resulting in pain that can be transient, temporarily worsening with exposure to heat, cold, or sweet foods and drinks.A tooth weakened by extensive internal decay can sometimes suddenly fracture under normal chewing forces. When the decay has progressed enough to allow the bacteria to overwhelm the pulp tissue in the center of the tooth a toothache can result and the pain will become more constant. Death of the pulp tissue and infection are common consequences. The tooth will no longer be sensitive to hot or cold, but can be very tender to pressure.
Dental caries can also cause bad breath and foul tastes. In highly progressed cases, infection can spread from the tooth to the surrounding soft tissues. Complications such as cavernous sinus thrombosis and Ludwig angina can be life-threatening.
Diagrammatic representation of acidogenic theory of etiology of dental caries. Four factors, namely, a suitable carbohydrate substrate.
(5). Saliva
(6) and fluoride.
There are four main criteria required for caries formation: a tooth surface (enamel or dentin), caries-causing bacteria, fermentable carbohydrates (such as sucrose), and time. However, it is also known that these four criteria are not always enough to cause the disease and a sheltered environment promoting development of a cariogenic biofilm is required. The caries process does not have an inevitable outcome, and different individuals will be susceptible to different degrees depending on the shape of their teeth, oral hygiene habits, and the buffering capacity of their saliva. Dental caries can occur on any surface of a tooth that is exposed to the oral cavity, but not the structures that are retained within the bone.
The bacteria most responsible for dental cavities are the mutans streptococci, most prominently Streptococcus mutans and Streptococcus sobrinus, and lactobacilli. If left untreated, the disease can lead to pain, tooth loss and infection.
Tooth decay disease is caused by specific types of bacteria that produce acid in the presence of fermentable carbohydrates such as sucrose, fructose, and glucose. The mineral content of teeth is sensitive to increases in acidity from the production of lactic acid. To be specific, a tooth (which is primarily mineral in content) is in a constant state of back-and-forth demineralization and remineralization between the tooth and surrounding saliva. For people with little saliva, especially due to radiation therapies and autoimmune disorders, such as Sjögren's syndrome, that may destroy the salivary glands, there also exists therapies such as saliva substitutes and remineralization products. These patients may be susceptible to dental caries. When the pH at the surface of the tooth drops below 5.5, demineralization proceeds faster than remineralization.
All caries occur from bacterial acid demineralization that exceeds saliva and fluoride remineralization, and acid demineralization occurs where bacterial plaque is left on teeth. Because most plaque-retentive areas are between teeth and inside pits and fissures on chewing surfaces where brushing is difficult, over 80% of cavities occur inside pits and fissures. Areas that are easily cleansed with a toothbrush, such as the front and back surfaces (facial and lingual), develop fewer cavities.
Some foods have an acidic pH of 5.5 or lower which can result in demineralisation in the absence of bacteria. This is known as erosion, rather than caries, because the acid is not bacterial in origin. Attack by acid from systemic complications such as bulimia and stomach difficulties as well as vomiting can cause tooth erosion.
Bacteria
The mouth contains a wide variety of oral bacteria, but only a few specific species of bacteria are believed to cause dental caries: Streptococcus mutans and Lactobacilli among them. These organisms can produce high levels of lactic acid following fermentation of dietary sugars, and are resistant to the adverse effects of low pH, properties essential for cariogenic bacteria. As the cementum of root surfaces is more easily demineralized than enamel surfaces, a wider variety of bacteria can cause root caries including Lactobacillus acidophilus, Actinomyces spp., Nocardia spp., and Streptococcus mutans. Bacteria collect around the teeth and gums in a sticky, creamy-coloured mass called plaque, which serves as a biofilm. Some sites collect plaque more commonly than others, for example sites with a low rate of salivary flow (molar fissures). Grooves on the occlusal surfaces of molar and premolar teeth provide microscopic retention sites for plaque bacteria, as do the interproximal sites. Plaque may also collect above or below the gingiva where it is referred to as supra- or sub-gingival plaque, respectively.
These bacterial strains, most notably S. mutans can be inherited by a child from a caretaker's kiss or through feeding premasticated food.
Fermentable carbohydrates
Bacteria in a person's mouth convert glucose, fructose, and most commonly sucrose (table sugar) into acids such as lactic acid through a glycolytic process called fermentation. If left in contact with the tooth, these acids may cause demineralization, which is the dissolution of its mineral content. The process is dynamic, however, as remineralization can also occur if the acid is neutralized by saliva or mouthwash. Fluoride toothpaste or dental varnish may aid remineralization. If demineralization continues over time, enough mineral content may be lost so that the soft organic material left behind disintegrates, forming a cavity or hole. The impact such sugars have on the progress of dental caries is called cariogenicity. Sucrose, although a bound glucose and fructose unit, is in fact more cariogenic than a mixture of equal parts of glucose and fructose. This is due to the bacteria utilising the energy in the saccharide bond between the glucose and fructose subunits. S.mutans adheres to the biofilm on the tooth by converting sucrose into an extremely adhesive substance called dextran polysaccharide by the enzyme dextransucranase.
Exposure
"Stephan curve", showing showing sudden decrease in plaque pH following glucose rinse, which returns to normal after 30-60 mins. Net demineralization of dental hard tissues occurs below the critical pH (5.5), shown in yellow.
The frequency of which teeth are exposed to cariogenic (acidic) environments affects the likelihood of caries development. After meals or snacks, the bacteria in the mouth metabolize sugar, resulting in an acidic by-product that decreases pH. As time progresses, the pH returns to normal due to the buffering capacity of saliva and the dissolved mineral content of tooth surfaces. During every exposure to the acidic environment, portions of the inorganic mineral content at the surface of teeth dissolves and can remain dissolved for two hours. Since teeth are vulnerable during these acidic periods, the development of dental caries relies heavily on the frequency of acid exposure.
The carious process can begin within days of a tooth's erupting into the mouth if the diet is sufficiently rich in suitable carbohydrates. Evidence suggests that the introduction of fluoride treatments have slowed the process. Proximal caries take an average of four years to pass through enamel in permanent teeth. Because the cementum enveloping the root surface is not nearly as durable as the enamel encasing the crown, root caries tends to progress much more rapidly than decay on other surfaces. The progression and loss of mineralization on the root surface is 2.5 times faster than caries in enamel. In very severe cases where oral hygiene is very poor and where the diet is very rich in fermentable carbohydrates, caries may cause cavities within months of tooth eruption. This can occur, for example, when children continuously drink sugary drinks from baby bottles (see later discussion).
Other risk factors.
Reduced salivary flow rate is associated with increased caries since the buffering capability of saliva is not present to counterbalance the acidic environment created by certain foods. As a result, medical conditions that reduce the amount of saliva produced by salivary glands, in particular the submandibular gland and parotid gland, are likely to dry mouth and thus to widespread tooth decay. Examples include Sjögren's syndrome, diabetes mellitus, diabetes insipidus, and sarcoidosis. Medications, such as antihistamines and antidepressants, can also impair salivary flow. Stimulants, most notoriously methylamphetamine ("meth mouth"), also occlude the flow of saliva to an extreme degree. Tetrahydrocannabinol, the active chemical substance in cannabis, also causes a nearly complete occlusion of salivation, known in colloquial terms as "cotton mouth". Moreover, 63% of the most commonly prescribed medications in the United States list dry mouth as a known side-effect. Radiation therapy of the head and neck may also damage the cells in salivary glands, somewhat increasing the likelihood of caries formation.
The use of tobacco may also increase the risk for caries formation. Some brands of smokeless tobacco contain high sugar content, increasing susceptibility to caries. Tobacco use is a significant risk factor for periodontal disease, which can cause the gingiva to recede. As the gingiva loses attachment to the teeth due to gingival recession, the root surface becomes more visible in the mouth. If this occurs, root caries is a concern since the cementum covering the roots of teeth is more easily demineralized by acids than enamel. Currently, there is not enough evidence to support a causal relationship between smoking and coronal caries, but evidence does suggest a relationship between smoking and root-surface caries.
Intrauterine and neonatal lead exposure promote tooth decay. Besides lead, all atoms with electrical charge and ionic radius similar to bivalent calcium, such as cadmium, mimic the calcium ion and therefore exposure may promote tooth decay.
Poverty is also a significant social determinant for oral health. Dental caries have been linked with lower socio-economic status and can be considered a disease of poverty.
Forms are available for risk assessment for caries when treating dental cases; this system using the evidence-based Caries Management by Risk Assessment (CAMBRA). It is still unknown if the identification of high-risk individuals can lead to more effective long-term patient management that prevents caries initiation and arrests or reverses the progression of lesions.
Pathophysiology
Animated image showing the shape progression of a caries lesion in the fissure of a tooth.
The progression of pit and fissure caries resembles two triangles with their bases meeting along the junction of enamel and dentin.
Enamel
Enamel is a highly mineralized acellular tissue, and caries act upon it through a chemical process brought on by the acidic environment produced by bacteria. As the bacteria consume the sugar and use it for their own energy, they produce lactic acid. The effects of this process include the demineralization of crystals in the enamel, caused by acids, over time until the bacteria physically penetrate the dentin. Enamel rods, which are the basic unit of the enamel structure, run perpendicularly from the surface of the tooth to the dentin. Since demineralization of enamel by caries, in general, follows the direction of the enamel rods, the different triangular patterns between pit and fissure and smooth-surface caries develop in the enamel because the orientation of enamel rods are different in the two areas of the tooth.
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| A Decayed Molar Tooth |
As the enamel loses minerals, and dental caries progresses, the enamel develop several distinct zones, visible under a light microscope. From the deepest layer of the enamel to the enamel surface, the identified areas are the: translucent zone, dark zones, body of the lesion, and surface zone. The translucent zone is the first visible sign of caries and coincides with a one to two percent loss of minerals. A slight remineralization of enamel occurs in the dark zone, which serves as an example of how the development of dental caries is an active process with alternating changes. The area of greatest demineralization and destruction is in the body of the lesion itself. The surface zone remains relatively mineralized and is present until the loss of tooth structure results in a cavitation.
Dentin
Unlike enamel, the dentin reacts to the progression of dental caries. After tooth formation, the ameloblasts, which produce enamel, are destroyed once enamel formation is complete and thus cannot later regenerate enamel after its destruction. On the other hand, dentin is produced continuously throughout life by odontoblasts, which reside at the border between the pulp and dentin. Since odontoblasts are present, a stimulus, such as caries, can trigger a biologic response. These defense mechanisms include the formation of sclerotic and tertiary dentin.
In dentin from the deepest layer to the enamel, the distinct areas affected by caries are the advancing front, the zone of bacterial penetration, and the zone of destruction. The advancing front represents a zone of demineralised dentine due to acid and has no bacteria present. The zones of bacterial penetration and destruction are the locations of invading bacteria and ultimately the decomposition of dentin. The zone of destruction has a more mixed bacterial population where proteolytic enzymes have destroyed the organic matrix. The innermost dentine caries has been reversibly attacked because the collagen matrix is not severely damaged, giving it potential for repair. The outer more superficial zone is highly infected with proteolytic degradation of the collagen matrix and as a result the dentine is irreversibly demineralised.
Animated image showing the shape progression of a caries lesion in the cervical region of a tooth.
The faster spread of caries through dentin creates this triangular appearance in smooth surface caries.
Sclerotic dentin
The structure of dentin is an arrangement of microscopic channels, called dentinal tubules, which radiate outward from the pulp chamber to the exterior cementum or enamel border. The diameter of the dentinal tubules is largest near the pulp (about 2.5 μm) and smallest (about 900 nm) at the junction of dentin and enamel. The carious process continues through the dentinal tubules, which are responsible for the triangular patterns resulting from the progression of caries deep into the tooth. The tubules also allow caries to progress faster.
In response, the fluid inside the tubules bring immunoglobulins from the immune system to fight the bacterial infection. At the same time, there is an increase of mineralization of the surrounding tubules. This results in a constriction of the tubules, which is an attempt to slow the bacterial progression. In addition, as the acid from the bacteria demineralizes the hydroxyapatite crystals, calcium and phosphorus are released, allowing for the precipitation of more crystals which fall deeper into the dentinal tubule. These crystals form a barrier and slow the advancement of caries. After these protective responses, the dentin is considered sclerotic.
Fluids within dentinal tubules are believed to be the mechanism by which pain receptors are triggered within the pulp of the tooth. Since sclerotic dentin prevents the passage of such fluids, pain that would otherwise serve as a warning of the invading bacteria may not develop at first. Consequently, dental caries may progress for a long period of time without any sensitivity of the tooth, allowing for greater loss of tooth structure.
Tertiary dentin
In response to dental caries, there may be production of more dentin toward the direction of the pulp. This new dentin is referred to as tertiary dentin. Tertiary dentin is produced to protect the pulp for as long as possible from the advancing bacteria. As more tertiary dentin is produced, the size of the pulp decreases. This type of dentin has been subdivided according to the presence or absence of the original odontoblasts. If the odontoblasts survive long enough to react to the dental caries, then the dentin produced is called "reactionary" dentin. If the odontoblasts are killed, the dentin produced is called "reparative" dentin.
In the case of reparative dentin, other cells are needed to assume the role of the destroyed odontoblasts. Growth factors, especially TGF-β, are thought to initiate the production of reparative dentin by fibroblasts and mesenchymal cells of the pulp. Reparative dentin is produced at an average of 1.5 μm/day, but can be increased to 3.5 μm/day. The resulting dentin contains irregularly shaped dentinal tubules that may not line up with existing dentinal tubules. This diminishes the ability for dental caries to progress within the dentinal tubules.
Cementum
The incidence of cemental caries increases in older adults as gingival recession occurs from either trauma or periodontal disease. It is a chronic condition that forms a large, shallow lesion and slowly invades first the root’s cementum and then dentin to cause a chronic infection of the pulp (see further discussion under classification by affected hard tissue). Because dental pain is a late finding, many lesions are not detected early, resulting in restorative challenges and increased tooth loss.
Diagnosis
Curved tip of a small metal probe, tapering to a point.
The tip of a dental explorer, which is used for caries diagnosis.
The presentation of caries is highly variable. However, the risk factors and stages of development are similar. Initially it may appear as a small chalky area (smooth surface caries), which may eventually develop into a large cavitation. Sometimes caries may be directly visible. However other methods of detection such as X-rays are used for less visible areas of teeth and to judge the extent of destruction. Lasers for detecting caries allow detection without ionizing radiation and are now used for detection of interproximal decay (between the teeth). Disclosing solutions are also used during tooth restoration to minimize the chance of recurrence.
Primary diagnosis involves inspection of all visible tooth surfaces using a good light source, dental mirror and explorer. Dental radiographs (X-rays) may show dental caries before it is otherwise visible, in particular caries between the teeth. Large dental caries are often apparent to the naked eye, but smaller lesions can be difficult to identify. Visual and tactile inspection along with radiographs are employed frequently among dentists, in particular to diagnose pit and fissure caries. Early, uncavitated caries is often diagnosed by blowing air across the suspect surface, which removes moisture and changes the optical properties of the unmineralized enamel.
Some dental researchers have cautioned against the use of dental explorers to find caries, in particular sharp ended explorers. In cases where a small area of tooth has begun demineralizing but has not yet cavitated, the pressure from the dental explorer could cause a cavity. Since the carious process is reversible before a cavity is present, it may be possible to arrest the caries with fluoride and remineralize the tooth surface. When a cavity is present, a restoration will be needed to replace the lost tooth structure.
At times, pit and fissure caries may be difficult to detect. Bacteria can penetrate the enamel to reach dentin, but then the outer surface may remineralize, especially if fluoride is present. These caries, sometimes referred to as "hidden caries", will still be visible on x-ray radiographs, but visual examination of the tooth would show the enamel intact or minimally perforated.
The differential diagnosis for dental caries includes dental fluorosis and developmental defects of the tooth including hypomineralization of the tooth and hypoplasia of the tooth.
Classification
Chart showing digitally drawn images of caries locations and their associated classifications.
G.V. Black Classification of Restorations
Caries can be classified by location, etiology, rate of progression, and affected hard tissues. These forms of classification can be used to characterize a particular case of tooth decay in order to more accurately represent the condition to others and also indicate the severity of tooth destruction. In some instances, caries are described in other ways that might indicate the cause.
Early childhood caries
Photograph of teeth and gums on the lower right hand side of the mouth showing large caries lesions on all teeth at the level of the gum
Rampant caries.
Early childhood caries (ECC) or "Baby bottle caries," "baby bottle tooth decay," or "Bottle Rot" is a pattern of decay found in young children with their deciduous (baby) teeth. The teeth most likely affected are the maxillary anterior teeth, but all teeth can be affected. The name for this type of caries comes from the fact that the decay usually is a result of allowing children to fall asleep with sweetened liquids in their bottles or feeding children sweetened liquids multiple times during the day.
Another pattern of decay is "rampant caries", which signifies advanced or severe decay on multiple surfaces of many teeth. Rampant caries may be seen in individuals with xerostomia, poor oral hygiene, stimulant use (due to drug-induced dry mouth, and/or large sugar intake. If rampant caries is a result of previous radiation to the head and neck, it may be described as radiation-induced caries. Problems can also be caused by the self-destruction of roots and whole tooth resorption when new teeth erupt or later from unknown causes.
Rate of progression
Temporal descriptions can be applied to caries to indicate the progression rate and previous history. "Acute" signifies a quickly developing condition, whereas "chronic" describes a condition that has taken an extended time to develop, in which thousands of meals and snacks, many causing some acid demineralization that is not remineralized, eventually results in cavities.
Recurrent caries, also described as secondary, are caries that appears at a location with a previous history of caries. This is frequently found on the margins of fillings and other dental restorations. On the other hand, incipient caries describes decay at a location that has not experienced previous decay. Arrested caries describes a lesion on a tooth that was previously demineralized but was remineralized before causing a cavitation. Fluoride treatment can help recalcification of tooth enamel as well as use of Amorphous calcium phosphate.
Affected hard tissue
Depending on which hard tissues are affected, it is possible to describe caries as involving enamel, dentin, or cementum. Early in its development, caries may affect only enamel. Once the extent of decay reaches the deeper layer of dentin, "dentinal caries" is used. Since cementum is the hard tissue that covers the roots of teeth, it is not often affected by decay unless the roots of teeth are exposed to the mouth. Although the term "cementum caries" may be used to describe the decay on roots of teeth, very rarely does caries affect the cementum alone. Roots have a very thin layer of cementum over a large layer of dentin, and thus most caries affecting cementum also affects dentin.
Prevention
Head of a toothbrush
Toothbrushes are commonly used to clean teeth.
Oral hygiene
Personal hygiene care consists of proper brushing and flossing daily.The purpose of oral hygiene is to minimize any etiologic agents of disease in the mouth. The primary focus of brushing and flossing is to remove and prevent the formation of plaque or dental biofilm. Plaque consists mostly of bacteria. As the amount of bacterial plaque increases, the tooth is more vulnerable to dental caries when carbohydrates in the food are left on teeth after every meal or snack. A toothbrush can be used to remove plaque on accessible surfaces, but not between teeth or inside pits and fissures on chewing surfaces. When used correctly, dental floss removes plaque from areas that could otherwise develop proximal caries but only if the depth of sulcus has not been compromised. Other adjunct oral hygiene aids include interdental brushes, water picks, and mouthwashes.
However oral hygiene is probably more effective at preventing gum disease (periodontal disease) than tooth decay. Food is forced inside pits and fissures under chewing pressure, leading to carbohydrate-fueled acid demineralisation where the brush, fluoride toothpaste, and saliva have no access to remove trapped food, neutralise acid, or remineralise demineralised tooth like on other more accessible tooth surfaces food to be trapped. (Occlusal caries accounts for between 80 and 90% of caries in children Chewing fibre like celery after eating forces saliva inside trapped food to dilute any carbohydrate like sugar, neutralise acid and remineralise demineralised tooth. The teeth at highest risk for carious lesions are the permanent first and second molars due to length of time in oral cavity and presence of complex surface anatomy.
Professional hygiene care consists of regular dental examinations and professional prophylaxis (cleaning). Sometimes, complete plaque removal is difficult, and a dentist or dental hygienist may be needed. Along with oral hygiene, radiographs may be taken at dental visits to detect possible dental caries development in high risk areas of the mouth, along with compliance to strict radiographic guidelines established by dental associations such as the American Dental Association and American Dental Hygienists' Association.
Dietary modification
For dental health, frequency of sugar intake is more important than the amount of sugar consumed.In the presence of sugar and other carbohydrates, bacteria in the mouth produce acids that can demineralize enamel, dentin, and cementum. The more frequently teeth are exposed to this environment the more likely dental caries are to occur. Therefore, minimizing snacking is recommended, since snacking creates a continuous supply of nutrition for acid-creating bacteria in the mouth. Also, chewy and sticky foods (such as dried fruit or candy) tend to adhere to teeth longer, and, as a consequence, are best eaten as part of a meal. Brushing the teeth after meals is recommended. For children, the American Dental Association and the European Academy of Paediatric Dentistry recommend limiting the frequency of consumption of drinks with sugar, and not giving baby bottles to infants during sleep (see earlier discussion). Mothers are also recommended to avoid sharing utensils and cups with their infants to prevent transferring bacteria from the mother's mouth.
It has been found that milk and certain kinds of cheese like cheddar cheese can help counter tooth decay if eaten soon after the consumption of foods potentially harmful to teeth. Also, chewing gum containing xylitol (a sugar alcohol) is widely used to protect teeth in many countries now. Xylitol's effect on reducing dental biofilm is, it is presumed, due to bacteria's inability to utilize it like other sugars. Chewing and stimulation of flavor receptors on the tongue are also known to increase the production and release of saliva, which contains natural buffers to prevent the lowering of pH in the mouth to the point where enamel may become demineralized.
Common dentistry trays used to deliver fluoride.
Fluoride is sold in tablets for cavity prevention.
Other measures
The use of dental sealants is a means of prevention. A sealant is a thin plastic-like coating applied to the chewing surfaces of the molars to prevent food from being trapped inside pits and fissures. This deprives resident plaque bacteria carbohydrate preventing the formation of pit and fissure caries. Sealants are usually applied on the teeth of children, as soon as the tooth erupt but adults are receiving them if not previously performed. Sealants can wear out and fail to prevent access of food and plaque bacteria inside pits and fissures and need to be replaced so they must be checked regularly by dental professionals.
Calcium, as found in food such as milk and green vegetables, is often recommended to protect against dental caries. Fluoride helps prevent decay of a tooth by binding to the hydroxyapatite crystals in enamel. The incorporated calcium makes enamel more resistant to demineralization and, thus, resistant to decay. Topical fluoride is now more highly recommended than systemic intake such as by tablets or drops to protect the surface of the teeth. This may include a fluoride toothpaste or mouthwash or varnish. Many dental professionals include application of topical fluoride solutions as part of routine visits and recommend the use of xylitol and Amorphous calcium phosphate products.
Vaccines are also under development.
An extracted tooth displaying an amalgam metal restoration on the occlusal surface
An amalgam used as a restorative material in a tooth.
Most importantly, whether the carious lesion is cavitated or noncavitated dictates the management. Clinical assessment of whether the lesion is active or arrested is also important. Noncavitated lesions can be arrested and remineralization can occur under the right conditions. However, this may require extensive changes to the diet (reduction in frequency of refined sugars), improved oral hygiene (toothbrushing twice per day with fluoride toothpaste and flossing), and regular application of topical fluoride. Such management of a carious lesion is termed "non-operative" since no drilling is carried out on the tooth. Non-operative treatment requires excellent understanding and motivation from the individual, otherwise the decay will continue.
Once a lesion has cavitated, especially if dentin is involved, remineralization is much more difficult and a dental restoration is usually indicated ("operative treatment"). Before a restoration can be placed, all of the decay must be removed otherwise it will continue to progress underneath the filling. Sometimes a small amount of decay can be left if it is entombed and the there is a seal which isolates the bacteria from their substrate. This can be likened to placing a glass container over a candle, which burns itself out once the oxygen is used up. Techniques such as stepwise caries removal are designed to avoid exposure of the dental pulp and overall reduction of the amount of tooth substance which requires removal before the final filling is placed. Often enamel which overlies decayed dentin must also be removed as it is unsupported and susceptible to fracture. The modern decision-making process with regards the activity of the lesion, and whether it is cavitated, is summarized in the table.
Destroyed tooth structure does not fully regenerate, although remineralization of very small carious lesions may occur if dental hygiene is kept at optimal level. For the small lesions, topical fluoride is sometimes used to encourage remineralization. For larger lesions, the progression of dental caries can be stopped by treatment. The goal of treatment is to preserve tooth structures and prevent further destruction of the tooth. Aggressive treatment, by filling, of incipient carious lesions, places where there is superficial damage to the enamel, is controversial as they may heal themselves, while once a filling is performed it will eventually have to be redone and the site serves as a vulnerable site for further decay.
In general, early treatment is quicker and less expensive than treatment of extensive decay. Local anesthetics, nitrous oxide ("laughing gas"), or other prescription medications may be required in some cases to relieve pain during or following treatment or to relieve anxiety during treatment. A dental handpiece ("drill") is used to remove large portions of decayed material from a tooth. A spoon, a dental instrument used to carefully remove decay, is sometimes employed when the decay in dentin reaches near the pulp. Once the decay is removed, the missing tooth structure requires a dental restoration of some sort to return the tooth to function and aesthetic condition.
Restorative materials include dental amalgam, composite resin, porcelain, and gold. Composite resin and porcelain can be made to match the color of a patient's natural teeth and are thus used more frequently when aesthetics are a concern. Composite restorations are not as strong as dental amalgam and gold; some dentists consider the latter as the only advisable restoration for posterior areas where chewing forces are great. When the decay is too extensive, there may not be enough tooth structure remaining to allow a restorative material to be placed within the tooth. Thus, a crown may be needed. This restoration appears similar to a cap and is fitted over the remainder of the natural crown of the tooth. Crowns are often made of gold, porcelain, or porcelain fused to metal.
A tooth with extensive caries eventually requiring extraction.
In certain cases, endodontic therapy may be necessary for the restoration of a tooth. Endodontic therapy, also known as a "root canal", is recommended if the pulp in a tooth dies from infection by decay-causing bacteria or from trauma. During a root canal, the pulp of the tooth, including the nerve and vascular tissues, is removed along with decayed portions of the tooth. The canals are instrumented with endodontic files to clean and shape them, and they are then usually filled with a rubber-like material called gutta percha. The tooth is filled and a crown can be placed. Upon completion of a root canal, the tooth is now non-vital, as it is devoid of any living tissue.
An extraction can also serve as treatment for dental caries. The removal of the decayed tooth is performed if the tooth is too far destroyed from the decay process to effectively restore the tooth. Extractions are sometimes considered if the tooth lacks an opposing tooth or will probably cause further problems in the future, as may be the case for wisdom teeth. Extractions may also be preferred by patients unable or unwilling to undergo the expense or difficulties in restoring the tooth.
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