Calculus :

Calculus :

In dentistry, calculus is a form of hardened Dental plaque and is synonymous with tartar. 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.
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. Routine dental visits are necessary so that calculus buildup can be professionally removed with ultrasonic tools and specialized sharp instruments.
- Clinical significance
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. Because dental plaque is the sole cause of periodontitis, it is referred to as the 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, 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. 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.

- Prevention
The best way to prevent the build up 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. Toothpaste with an additive ingredient of zinc citrate will also aid in preventing tartar build-up and control it.
- Sub-gingival calculus formation and chemical dissolution
Sub-gingival calculus (tartar) is comprised almost entirely of two components: Fossilized anaerobic bacteria whose biologic composition has been replaced by calcium phosphate salts, and otherwise free floating 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 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

References
1. ^ "Paramater on Systemic Conditions Affected by Periodontal Diseases". J Periodontol 71: 880-883. 2000. http://www.perio.org/resources-products/pdf/880.pdf. Retrieved 2007-07-30.