Dental caries
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Dental caries, also known colloquially as tooth decay or dental cavities, is a disease of the teeth resulting in damage to tooth structure. The occurrence of dental caries is widespread globally, and the disease can lead to pain, tooth loss, infections, and, in severe cases, death. The number of cases has decreased in some countries, usually attributed to better oral hygiene and greater preventive measures, such as fluoride exposure. In less developed areas of the world, dental caries continues to be a problem.
Causes
Four factors are necessary for caries to occur: a tooth surface (enamel or dentine); cariogenic (or potentially caries-causing) bacteria; fermentable carbohydrates (such as sucrose); and time.Soames, J.V. and Southam, J.C. (1993). Oral Pathology, second edition, chapter 2 - Dental Caries.
The mouth contains a wide variety of bacteria, but only a few specific species of bacteria are believed to cause dental caries: Streptococcus mutans and Lactobacilli among themHardie, J.M. (1982). The microbiology of dental caries. Dental Update, 9, 199-208.. The bacteria collect around the teeth and gums in a sticky creamy-coloured mass called plaque. The bacteria convert sugars (most commonly sucrose - or common sugar, glucose and fructose) into acids such as lactic acid created through fermentation processesHolloway, P.J. (1983). The role of sugar in the aetiology of dental caries. Journal of Dentistry, 11, 189-213.. If left in contact with the tooth these acids cause the dissolution of its mineral content, or demineralisation.
The process is dynamic however. That is, remineralisation can also occur if the acid is buffered (or 'neutralised') and suitable minerals are available in the mouth (from saliva but also from preventative aids such as fluoride toothpaste, varnish or mouthwash)Silverstone, L.M. (1983). Remineralization and dental caries: new concepts. Dental Update, 10, 261-273.. Caries may be arrested at this stage i.e. before a cavity is formed. If sufficient acid is produced over a period of time to tip the balance in favour of demineralisation, caries will progress, and may then result in so much mineral content being lost that the soft organic material left behind will disintegrate and a cavity, or hole, form.
Dental caries can occur on any surface of a tooth that is exposed to the oral cavity (i.e. not that bit which is retained within the bone)Kidd, E.A.M. and Smith, B.G.N. (1990). Pickard's Manual of Operative Dentistry, Sixth Edition. Chapter 1 - Why restore teeth?.. However certain sites are more common than others because they make retention of plaque bacteria easier. The grooves on the biting surfaces of molar and premolar teeth provide microscopic retention, as does the point of contact between teeth. Plaque may also collect more along the gingival (or 'gum') margin. In addition, the edges of fillings or crowns can provide protection for bacteria, as can intraoral appliances such as orthodontic braces or removable partial dentures. Also, dentine may be more susceptible to caries than enamel because it has a lower mineral contentMellberg, J.R. (1986). Demineralization and remineralization of root surface caries. Gerodontology, 5, 25-31.. Thus the root surfaces of teeth are generally more vulnerable to caries once they become exposed over time from gingival (or 'gum') recession and periodontal disease.
The carious process can begin within days of a tooth erupting into the mouth, if the diet is sufficiently rich in suitable carbohydrates, but may begin at any other time during the course of a life. The speed of the process is dependant on the interplay of the various factors described above. In very severe cases where oral hygiene is very poor (resulting in large quantities of bacteria) and/or where the diet is very rich in fermentable carbohydrates on a regular basis the caries may cause cavitation in months and is called rampant caries and affect all tooth surfaces. (This is seen, for example, when young children continuously suck a sugary drink from a bottle.) On the other hand it may take years before the process results in a cavity being formed, if at all.
The caries process is not an inevitable one and different individuals will be susceptible to different degrees depending on, amongst other things, the mineral composition of their enamel and dentine, their age, the shape of their teeth, their diet, their oral hygiene, and the buffering capacity of their saliva.
Signs and symptoms
- toothache (technically called odontalgia or odontalgy)-- particularly after sweet or hot or cold foods or drinks (sensitivity)
- visible pits or holes (cavities) in the teeth
- halitosis (bad breath)
Most dental caries are discovered in the early stages during routine checkups. The surface of the tooth may be soft when probed with a sharp instrument, such as a dental explorer. Pain may not be present until the advanced stages of tooth decay, when the bacterial infection reaches the deeper layers of the tooth and begins to involve the nerve fibers at or near the pulp. Dental radiographs, produced when X-rays are shot through the jaw and picked up on film, may show some cavities before they are visible to the eye.
An image showing various stages of dental caries is shown [here].
Types of dental caries
Caries can be classified into different broad categories based on its location. Two general distinctions made between caries are those found on smooth surfaces and those found in pit and fissures.Summit, James B., J. William Robbins, and Richard S. Schwartz. "Fundamentals of Operative Dentistry: A Contemporary Approach." 2nd edition. Carol Stream, Illinois, Quintessence Publishing Co, Inc, 2001, p. 30. ISBN 0867153822.. The location, initiation, and progression of these types of lesions differ between each other.
More specifically, carious lesions can be accurately described by their particular location on the tooth's surfaces. "Occlusal" caries are found on the chewing surfaces, "facial" caries are on surfaces nearest the cheeks or lips, and "lingual" caries are on the surfaces facing the tongue. The location of facial caries is sometimes described as "buccal" when found on the surfaces of posterior teeth nearest the cheeks and as "labial" when found on the surfaces of anterior teeth nearest the lips.
Cavities that occur on the root usually occur when gross decay on the facial or lingual surfaces extends apically (towards the root, or the apex) past the CEJ (cementoenamel junction) or when the root surfaces have been exposed due to gingival recession. 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 aggressively than decay on other surfaces.
Diagnosis of caries
Large dental cavities are often visually apparent. Smaller cavities may require examination with magnification and visible light, dental explorer, or imaging with dental radiographs. A laser can be used as an adjunct for the diagnosis of smaller cases of caries in the pits and fissures of the teeth.
Treatment
Destroyed tooth structure does not fully regenerate, although remineralization of very small cavities may occur if dental hygiene is kept at optimal level. Moreover, the progression of dental caries can be stopped by treatment. The goal of treatment is to preserve the tooth and prevent complications.
Traditionally, a dental drill is used to remove decayed material from a tooth. Once the decay is removed, a portion of the tooth is missing, and a dental restoration of some type is placed to restore the tooth to function.
In filling teeth, the decayed material is removed (by drilling and/or scraping) and replaced with dental fillings, made of a restorative material such as composite resin, porcelain, dental amalgam or gold. Composite resin and porcelain can be made to match the color of a patient's natural teeth, and are thus indicated in aesthetic areas (the front of the mouth). However, composite restorations may be too weak to withstand the cyclic forces that are naturally placed on the occlusal (chewing) surface of posterior teeth. Some dentists therefore consider dental amalgam and gold the only advisable intracoronal restoration ("filling") for the biting surface of posterior teeth (premolars and molars). Composites also undergo polymerization shrinkage, (that is, they shrink when they polymerize, or harden), and they pull away from the walls and margins of the cavity preparation, leaving an opening for bacteria to enter and cause recurrent decay.
Crowns are used if decay is extensive enough to preclude an intracoronal restoration (filling). Simply put, if there is not enough tooth structure remaining after the decay is removed, a restorative material cannot be placed within the remaining tooth structure. The restorative material must be fashioned into a sort of cap that encloses the remaining tooth structure. This "cap," or crown, is fitted over the remainder of the natural crown of the tooth. Crowns are often made of gold, porcelain or porcelain fused to metal (PFM). In certain cases, it may be necessary for root canal therapy to be performed on a tooth in order to place a crown.
Root canal therapy (also called "endodontic therapy") is recommended if the nerve (pulp) in a tooth dies (i.e. pulpal necrosis) and the tooth has a functional role in the dentition. Pulpal necrosis can occur as a result of infection of the pulp with decay-causing bacteria as well as from the unavoidable trauma associated with excavation of caries near the pulp. There are also pathologic processes that occur within the supporting bone that may result in death of the pulp. Traumatic injuries to teeth (such as those that might occur while playing contact sports) are also known causes of pulpal necrosis. During a root canal, the pulp of the tooth, including the nerve and vascular (blood vessel) tissue, is removed along with decayed portions of the tooth. The canals in which the pulpal tissue resided are subsequently instrumented with endodontic files (rasps which clean and shape the canals), and are then filled with a rubber-like material called "gutta percha". The tooth is filled and a crown may be placed over the tooth if needed. Upon completion of a root canal, the tooth is now "non-vital", as it is devoid of any living tissue.
Removal of the decayed tooth, an extraction is performed if the tooth is too far destroyed from the decay process to effectively restore, or if the tooth is considered non-functional (e.g. wisdom teeth frequently, teeth that lack an opposing tooth, or a tooth in a non-useful position) or the patient does not wish to undergo the expense or procedure of restoring the tooth.
Expectations
Treatment often preserves the tooth. Early treatment is less painful and less expensive than treatment of extensive decay. Anesthetics -- local, nitrous oxide ("laughing gas"), or other prescription medications -- may be required in some cases to relieve pain during or following drilling or other treatment of decayed teeth. For those who fear dental treatment, nitrous oxide anesthesia may be preferred.
Prevention
Oral hygiene is the primary prevention against dental caries. This consists of personal care (proper brushing at least twice a day and flossing at least daily) and professional care (regular dental examination and cleaning, every 6 months). Select X-rays may be taken yearly to detect possible cavity development in high risk areas of the mouth.
For those who are more meticulous about caring for their teeth, it is best to brush not just twice per day but after every act of consuming refined carbohydrate products that stick to the teeth after eating them. For example, if one snacks on oreo cookies or potato chips 5 times per day, one should brush 5 times a day, after every incident of eating these snacks, since they stick to the teeth after eating them. The continued presence of refined simple carbohydrates or sugars stuck to the teeth after eating them gives bacteria a continuous supply of sugar to make acids that break down teeth. Someone who snacks numerous times per day on these substances is likely to continue to get tooth decay in spite of brushing twice per day. If one cannot brush immediately after consuming refined carbohydrates that stick to teeth, one should try to remove as much of them as possible from the teeth using a toothpick, then try to rinse out with water. As a general rule of thumb, do not allow your teeth to have food particles stuck to them at any time.
Chewy, sticky foods (such as dried fruit or candy) are best if eaten as part of a meal rather than as a snack. If possible, brush the teeth or rinse the mouth with water after eating these foods. Minimize snacking, which creates a constant supply of acid in the mouth. Avoid constant sipping of sugary drinks or frequent sucking on candy and mints.
The use of dental sealants is a good means of cavity prevention. Sealants are thin plastic-like coating applied to the chewing surfaces of the molars. This coating prevents the accumulation of plaque in the deep grooves on these vulnerable surfaces. Sealants are usually applied on the teeth of children, shortly after the molars erupt. Older people may also benefit from the use of tooth sealants.
Fluoride is often recommended to protect against dental caries. It has been demonstrated that people who ingest fluoride in their drinking water or by fluoride supplements have fewer dental caries. Fluoride ingested when the teeth are developing is incorporated into the structure of the enamel and protects it against the action of acids.
Topical fluoride is also recommended to protect the surface of the teeth. This may include a fluoride toothpaste or mouthwash. Many dentists include application of topical fluoride solutions as part of routine visits.
Chewing gum containing xylitol, wood sugar, is widely used to protect teeth in some countries, being especially popular in the Finnish candy industry. Its effect on reducing plaque is believed to be based on bacteria not being able to utilize it like other sugars.
It has also been found that certain kinds of cheese like cheddar or milk can help counter tooth decay if eaten soon after having eaten foods potentially harmful for teeth.
Furthermore, recent research shows that low intensity laser radiation of argon-ion lasers may prevent the susceptibility for enamel caries and white spot lesions, as indicated in the publications below.
Lastly, a vaccine for dental caries has been researched through previous years, but no effective vaccine has been created yet. Research is currently ongoing.
References
External links
- [What causes cavities; an indepth look]
- [Links to tooth decay pictures (Hardin MD/Univ of Iowa)]
- [Caries Diagnosis - Coronal Caries] from the University of Michigan, School of Dentistry
See also
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