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In dentistry, calculus or tartar is a form of hardened dental plaque. It is caused by the continual accumulation of minerals from saliva on plaque on the teeth. Its rough surface provides an ideal medium for further plaque formation, threatening the health of the gingiva (gums).
Brushing and flossing can remove plaque from which calculus forms; however, once formed, it is too hard and firmly attached to be removed with a toothbrush. Calculus buildup can be removed with ultrasonic tools or unique hand instruments (such as a periodontal scaler).
Calcis, in Greek, was a term used for various kinds of stones, coming from the term for limestone. This spun off many modern words, including "calculate" (use stones for mathematical purposes), and "calculus", which came to be used, in the 18th century, for accidental or incidental mineral buildups in human and animal bodies, like kidney stones and minerals on teeth.
Tartar, on the other hand, originates in Greek as well, but as the term for the white encrustation inside casks, aka potassium bitartrate commonly known as cream of tartar. This came to be a term used for calcium phosphate on teeth in the early 19th century.
Plaque accumulation causes the gingiva to become irritated and inflamed, and this is referred to as gingivitis. When the gingiva become so irritated that there is a loss of the connective tissue fibers that attach the gums to the teeth and bone that surrounds the tooth, this is known as periodontitis. Dental plaque is not the sole cause of periodontitis, however it is many times referred to as a primary aetiology. Plaque that remains in the oral cavity long enough will eventually calcify and become calculus. Calculus is detrimental to gingival health because it serves as a trap for increased plaque formation and retention; thus, calculus, along with everything else that causes a localized build-up of plaque, is referred to as a secondary etiology of periodontitis.
Calculus can form both along the gumline, where it is referred to as supragingival ("above the gum"), and within the narrow sulcus that exists between the teeth and the gingiva, where it is referred to as subgingival ("below the gum"). Calculus formation can result in a number of clinical manifestations, including bad breath, receding gums and chronically inflamed gingiva.
When plaque is supragingival, the bacterial content consists mostly of aerobic bacteria and yeast, or those bacteria which utilize and can survive in an environment containing oxygen. Subgingival plaque, however, is composed mainly of anaerobic bacteria, or those bacteria which cannot exist in an environment containing oxygen. Anaerobic bacteria are especially dangerous to the gingiva and the gingival fibers that attach the teeth to the gums, leading to periodontitis. Calculus tartar paste is commonly exhibited by humans. Almost all individuals with periodontitis exhibit considerable subgingival calculus deposits. These anaerobic bacteria have been linked to cardiovascular disease and mothers giving birth to pre-term low weight babies, but there is no conclusive evidence yet that periodontitis is a significant risk factor for either of these two conditions.
The best way to prevent the buildup of calculus is through twice daily toothbrushing and flossing and regular cleaning visits based on a schedule recommended by the dental health care provider. Calculus accumulates more easily in some individuals, requiring more frequent brushing and dental visits. There are also some external factors that facilitate the accumulation of calculus, including smoking and diabetes. While toothpaste with an additive ingredient of zinc citrate has been shown to produce a statistically significant reduction in plaque accumulation, it is of such a small degree that its clinical importance is questionable.
Sub-gingival calculus (tartar) is composed almost entirely of two components: fossilized anaerobic bacteria whose biologic composition has been replaced by calcium phosphate salts, and calcium phosphate salts that have joined the fossilized bacteria in calculus formations. The initial attachment mechanism and the development of mature calculus formations are based on electrical charge. Unlike calcium phosphate, the primary component of teeth, calcium phosphate salts exist as electrically unstable ions. The following minerals are detectable in calculus by X-ray diffraction: brushite (CaHPO4·2H2O), octacalcium phosphate (Ca8H2(PO4)6.5H2O), magnesium-containing whitlockite (Ca9(MgFe)(PO4)6PO3OH), and carbonate-containing hydroxyapatite (approximately Ca5(PO4)3(OH) but containing some carbonate).
The reason fossilized bacteria are initially attracted to one part of the subgingival tooth surface over another is not fully understood; once the first layer is attached, ionized calculus components are naturally attracted to the same places due to electrical charge. The fossilized bacteria pile on top of one another, in a rather haphazard manner. All the while, free-floating ionic components fill in the gaps left by the fossilized bacteria. The resultant hardened structure can be compared to concrete; with the fossilized bacteria playing the role of aggregate, and the smaller calcium phosphate salts being the cement. The once purely electrical association of fossilized bacteria then becomes mechanical, with the introduction of free-floating calcium phosphate salts. The "hardened" calculus formations are at the heart of periodontal disease and treatment.
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