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How Subgingival Calculus Forms And How To Prevent It

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Medically Reviewed By Colgate Global Scientific Communications

When plaque builds up in your mouth, it can turn into an even greater dental health threat: calculus. This formation, also known as tartar, is a calcified mass that adheres to your teeth. Calculus is classified as either supragingival or subgingival, depending on its location on your teeth. If left unremoved, subgingival calculus can lead to gum disease and tooth loss.

How Calculus Develops

An article published in the International Journal of Dental and Health Sciences (IJDHS) explains that plaque, which is a sticky film of bacteria that constantly forms on your teeth, can mineralize due to the exchange of calcium and phosphate ions present in your saliva. This process is what creates calculus, a hard mass of bacteria stuck to your tooth surfaces.

Plaque can harden into calculus in as little as four to eight hours. The average length of time for mineralization, however, is 10 to 12 days. Calcification times can vary from person to person, depending on their salivary pH and the amount of calcium and other substances in their saliva. Once calculus forms, it then attracts more plaque, which in time can become another layer of calcified material.

Characteristics of Subgingival Calculus

Tartar that accumulates on your teeth above the gumline and is easily seen by your dentist or dental hygienist is called supragingival calculus, according to the IJDHS article. But the tartar that forms below the gumline — and is therefore not immediately visible — is known as subgingival calculus. This type of calculus is usually dark brown to greenish black in color and can be detected with a dental instrument called an explorer.

It's important to note that, while you can clean plaque off your teeth with brushing and flossing, hard tartar can only be removed by a professional cleaning, explains the American Academy of Periodontology (AAP). Your dentist or dental hygienist uses special instruments that are designed to remove the calculus.

Calculus and Periodontal Disease

Calculus, including subgingival calculus, is associated with gingivitis, which is the first stage of gum disease, according to a review in the Journal of Health Sciences & Research (JOHSR). Typical early-stage gum disease symptoms include red, swollen gums and minor bleeding, according to the AAP. Luckily, the condition is often reversible with a good home care routine.

If left untreated, gingivitis can turn into periodontitis, where the plaque continues to spread beneath the gumline. When this happens, the AAP notes that the gum tissue eventually begins to pull away from the teeth, forming pockets that get infected. Pockets between the teeth and gums deeper than 4 millimeters may indicate that you have periodontitis, notes the Mayo Clinic.

When tartar builds up in the pocket, the bacteria can destroy the surrounding bone and tissue structures. Treatment of periodontitis usually involves scaling and root planing to remove all of the tartar, explains the Mayo Clinic. Periodontal surgery may also be necessary to treat any bone loss.

Preventing Calculus Formation

Since plaque is what forms tartar, preventing calculus involves cleaning plaque off your teeth regularly to prevent mineralization. This is why it's important to maintain a good oral care routine at home. Be sure to brush your teeth twice a day and floss daily. Using an antimicrobial mouthrinse can also help to reduce the amount of bacteria in your mouth. In addition, you should visit your dentist every six months for dental cleanings. At these cleanings, your dentist or dental hygienist will remove any tartar to prevent inflammation and gum disease.

While subgingival calculus can cause serious dental complications, it's one battle you can win if you keep up with good dental health habits.


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This article is intended to promote understanding of and knowledge about general oral health topics. It is not intended to be a substitute for professional advice, diagnosis or treatment. Always seek the advice of your dentist or other qualified healthcare provider with any questions you may have regarding a medical condition or treatment.

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