dentistry Dentistry, also known as dental medicine and oral medicine, is the branch of medicine focused on the teeth, gums, and mouth. It consists of the study, diagnosis, prevention, management, and treatment of diseases, disorders, and conditions o ...

, calculus or tartar is a form of hardened

dental plaque Dental plaque is a biofilm of microorganisms (mostly bacteria, but also fungi) that grows on surfaces within the mouth. It is a sticky colorless deposit at first, but when it forms tartar, it is often brown or pale yellow. It is commonly found bet ...

. It is caused by precipitation of minerals from

saliva Saliva (commonly referred to as spit) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be ...

and

gingival crevicular fluid The gums or gingiva (plural: ''gingivae'') consist of the mucosal tissue that lies over the mandible and maxilla inside the mouth. Gum health and disease can have an effect on general health. Structure The gums are part of the soft tissue linin ...

(GCF) in plaque on the

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

. This process of precipitation kills the bacterial cells within dental plaque, but the rough and hardened surface that is formed provides an ideal surface for further plaque formation. This leads to calculus buildup, which compromises the health of the

gingiva The gums or gingiva (plural: ''gingivae'') consist of the mucosal tissue that lies over the mandible and maxilla inside the mouth. Gum health and disease can have an effect on general health. Structure The gums are part of the soft tissue lini ...

(gums). 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 is associated with a number of clinical manifestations, including

bad breath Bad breath, also known as halitosis, is a symptom in which a noticeably unpleasant breath odour is present. It can result in anxiety among those affected. It is also associated with depression and symptoms of obsessive compulsive disorder. Th ...

, receding gums and chronically inflamed gingiva. Brushing and flossing can remove plaque from which calculus forms; however, once formed, calculus is too hard (firmly attached) to be removed with a toothbrush. Calculus buildup can be removed with ultrasonic tools or dental hand instruments (such as a

periodontal scaler Periodontal scalers are dental instruments used in the prophylactic and periodontal care of teeth (most often human teeth), including scaling and root planing. The working ends come in a variety of shapes and sizes, but they are always narrow at ...

Etymology

The word comes from Latin ''calculus'' "small stone", from ''calx'' "limestone, lime", probably related to Greek ''chalix'' "small stone, pebble, rubble", which many trace to a Proto-Indo-European root for "split, break up". ''Calculus'' was a term used for various kinds of stones. 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 (''tartaron''), but as the term for the white encrustation inside casks (a.k.a.

potassium bitartrate Potassium bitartrate, also known as potassium hydrogen tartrate, with formula K C4 H5 O6, is a byproduct of winemaking. In cooking, it is known as cream of tartar. It is processed from the potassium acid salt of tartaric acid (a carboxylic ac ...

, commonly known as

cream of tartar Potassium bitartrate, also known as potassium hydrogen tartrate, with formula K C4 H5 O6, is a byproduct of winemaking. In cooking, it is known as cream of tartar. It is processed from the potassium acid salt of tartaric acid (a carboxylic ac ...

). This came to be a term used for

calcium phosphate The term calcium phosphate refers to a family of materials and minerals containing calcium ions (Ca2+) together with inorganic phosphate anions. Some so-called calcium phosphates contain oxide and hydroxide as well. Calcium phosphates are whi ...

on teeth in the early 19th century.

Calculus composition

Calculus is composed of both inorganic (mineral) and organic (cellular and extracellular matrix) components. The mineral proportion of calculus ranges from approximately 40–60%, depending on its location in the dentition, and consists primarily of

crystals organized into four principal mineral phases, listed here in order of decreasing ratio of phosphate to calcium: *

whitlockite Whitlockite is a mineral, an unusual form of Tricalcium phosphate, calcium phosphate. Its formula is Ca9(Mgiron, Fe)(PO4)6PO3Ohydrogen, H. It is a relatively rare mineral but is found in granitic pegmatites, phosphate rock deposits, guano caves a ...

, *

hydroxyapatite Hydroxyapatite, also called hydroxylapatite (HA), is a naturally occurring mineral form of calcium apatite with the formula Ca5(PO4)3(OH), but it is usually written Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two entities. ...

, *

octacalcium phosphate Octacalcium phosphate (sometimes referred to as OCP) is a calcium phosphate with a formula Ca8H2(PO4)6⋅5H2O. OCP may be a precursor to tooth enamel, dentine, and bones. OCP is a precursor of hydroxylapatite (HAP), an inorganic biomineral that ...

, *and

brushite Brushite is a phosphate mineral with the chemical formula . Crystals of the pure compound belong to the monoclinic space group C2/c and are colorless. Cell density within dental plaque and calculus is very high, consisting of an estimated 200,000,000 cells per milligram. The cells within calculus are primarily bacterial, but also include at least one species of archaea ('' Methanobrevibacter oralis'') and several species of yeast (e.g., ''

Candida albicans ''Candida albicans'' is an opportunistic pathogenic yeast that is a common member of the human gut flora. It can also survive outside the human body. It is detected in the gastrointestinal tract and mouth in 40–60% of healthy adults. It is us ...

''). The organic extracellular matrix in calculus consists primarily of

proteins Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

and

lipids Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...

(fatty acids, triglycerides, glycolipids, and phospholipids), as well as extracellular DNA. Trace amounts of host, dietary, and environmental microdebris are also found within calculus, including salivary proteins, plant DNA, milk proteins, starch granules, textile fibers, and smoke particles.

Calculus formation

The processes of calculus formation from dental plaque are not well understood. Supragingival calculus formation is most abundant on the buccal (cheek) surfaces of the maxillary (upper jaw)

molars The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...

and on the lingual (tongue) surfaces of the

mandibular In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

(lower jaw)

incisors Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wh ...

. These areas experience high salivary flow because of their proximity to the parotid and sublingual

salivary glands The salivary glands in mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands ( parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands. Salivary gl ...

. Subgingival calculus forms below the gumline and is typically darkened in color by the presence of black-pigmented bacteria, whose cells are coated in a layer of iron obtained from heme during gingival bleeding. Dental calculus typically forms in incremental layers that are easily visible using both electron microscopy and

light microscopy Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye (objects that are not within the resolution range of the normal eye). There are three well-known branches of micr ...

. These layers form during periodic calcification events of the dental plaque, but the timing and triggers of these events are poorly understood. The formation of calculus varies widely among individuals and at different locations within the mouth. Many variables have been identified that influence the formation of dental calculus, including age, gender, ethnic background, diet, location in the oral cavity, oral hygiene, bacterial plaque composition, host genetics, access to professional dental care, physical disabilities, systemic diseases, tobacco use, and drugs and medications.

Clinical significance

Plaque Plaque may refer to: Commemorations or awards * Commemorative plaque, a plate or tablet fixed to a wall to mark an event, person, etc. * Memorial Plaque (medallion), issued to next-of-kin of dead British military personnel after World War I * Pla ...

accumulation causes the

to become irritated and inflamed, and this is referred to as

gingivitis Gingivitis is a non-destructive disease that causes inflammation of the gums. The most common form of gingivitis, and the most common form of periodontal disease overall, is in response to bacterial biofilms (also called plaque) that is attached ...

. When the gingiva become so irritated that there is a loss of the

connective tissue Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tiss ...

fibers Fiber or fibre (from la, fibra, links=no) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate ...

that attach the gums to the teeth and bone that surrounds the tooth, this is known as

periodontitis Periodontal disease, also known as gum disease, is a set of inflammatory conditions affecting the tissues surrounding the teeth. In its early stage, called gingivitis, the gums become swollen and red and may bleed. It is considered the main cau ...

. Dental plaque is not the sole cause of periodontitis; however it is many times referred to as a primary

aetiology Etiology (pronounced ; alternatively: aetiology or ætiology) is the study of causation or origination. The word is derived from the Greek (''aitiología'') "giving a reason for" (, ''aitía'', "cause"); and ('' -logía''). More completely, e ...

. 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 other factors that cause a localized build-up of plaque, is referred to as a secondary aetiology of periodontitis. When plaque is supragingival, the bacterial content contains a great proportion of

aerobic bacteria Aerobic means "requiring air," in which "air" usually means oxygen. Aerobic may also refer to * Aerobic exercise, prolonged exercise of moderate intensity * Aerobics, a form of aerobic exercise * Aerobic respiration, the aerobic process of cell ...

and

yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitut ...

, or those bacteria which utilize and can survive in an environment containing

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

. Subgingival plaque contains a higher proportion of

anaerobic bacteria An anaerobic organism or anaerobe is any organism that does not require molecular oxygen for growth. It may react negatively or even die if free oxygen is present. In contrast, an aerobic organism (aerobe) is an organism that requires an oxygenat ...

, or those bacteria which cannot exist in an environment containing oxygen. Several anaerobic plaque bacteria, such as ''

Porphyromonas gingivalis ''Porphyromonas gingivalis'' belongs to the phylum ''Bacteroidota'' and is a nonmotile, Gram-negative, rod-shaped, anaerobic, pathogenic bacterium. It forms black colonies on blood agar. It is found in the oral cavity, where it is implicate ...

'', secrete antigenic proteins that trigger a strong inflammatory response in the

periodontium The periodontium is the specialized tissues that both surround and support the teeth, maintaining them in the maxillary and mandibular bones. The word comes from the Greek terms περί ''peri''-, meaning "around" and -''odont'', meaning "tooth" ...

, the specialized tissues that surround and support the teeth. Prolonged inflammation of the periodontium leads to bone loss and weakening of the

gingival fibers The gingival fibers are the connective tissue fibers that inhabit the gingival tissue adjacent to teeth and help hold the tissue firmly against the teeth. They are primarily composed of type I collagen, although type III fibers are also involved ...

that attach the teeth to the gums, two major hallmarks of periodontitis. Supragingival calculus formation is nearly ubiquitous in humans, but to differing degrees. Almost all individuals with periodontitis exhibit considerable subgingival calculus deposits. Dental plaque bacteria have been linked to

cardiovascular disease Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, h ...

and mothers giving birth to pre-term low weight infants, but there is no conclusive evidence yet that periodontitis is a significant risk factor for either of these two conditions.

Prevention

Toothpaste Toothpaste is a paste or gel dentifrice used with a toothbrush to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it is an abrasive that aids in removing dental plaque and food from the teeth, ...

with

pyrophosphate In chemistry, pyrophosphates are phosphorus oxyanions that contain two phosphorus atoms in a P–O–P linkage. A number of pyrophosphate salts exist, such as disodium pyrophosphate (Na2H2P2O7) and tetrasodium pyrophosphate (Na4P2O7), among other ...

s or zinc citrate has been shown to produce a statistically significant reduction in plaque accumulation, but the effect of zinc citrate is so modest that its clinical importance is questionable. Some calculus may form even without plaque deposits, by direct mineralisation of the pellicle.

Calculus in other animals

Calculus formation in other animals is less well studied than in humans, but it is known to form in a wide range of species. Domestic pets, such as

dogs The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...

and cats, frequently accumulate large calculus deposits. Animals with highly abrasive diets, such as

ruminants Ruminants (suborder Ruminantia) are hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. The ...

and

equids Equidae (sometimes known as the horse family) is the taxonomic family of horses and related animals, including the extant horses, asses, and zebras, and many other species known only from fossils. All extant species are in the genus '' Equus'', ...

, rarely form thick deposits and instead tend to form thin calculus deposits that often have a metallic or opalescent sheen. In animals, calculus should not be confused with crown

cementum Cementum is a specialized calcified substance covering the root of a tooth. The cementum is the part of the periodontium that attaches the teeth to the alveolar bone by anchoring the periodontal ligament.Illustrated Dental Embryology, Histology, a ...

, a layer of calcified dental tissue that encases the tooth root underneath the gingival margin and is gradually lost through periodontal disease.

Archaeological significance

Dental calculus has been shown to contain well preserved microparticles, DNA and

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

in archaeological samples. The information these molecules contain can reveal information about the oral microbiome of the host and the presence of pathogens. It is also possible to identify dietary sources as well as study dietary shifts and occasionally evidence of craft activities.

Sub-gingival calculus formation and chemical dissolution

Sub-gingival calculus is composed almost entirely of two components: fossilized anaerobic bacteria whose biological composition has been replaced by

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 Brushite is a phosphate mineral with the chemical formula . Crystals of the pure compound belong to the monoclinic space group C2/c and are colorless.octacalcium phosphate Octacalcium phosphate (sometimes referred to as OCP) is a calcium phosphate with a formula Ca8H2(PO4)6⋅5H2O. OCP may be a precursor to tooth enamel, dentine, and bones. OCP is a precursor of hydroxylapatite (HAP), an inorganic biomineral that ...

(), magnesium-containing

(), and carbonate-containing

(approximately 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.

Removal of calculus after formation

As mentioned above in the clinical significance section, plaque and calculus deposits are a major etiological factor in the development and progression of oral disease. An important part of the scope of practice of a dental hygienist is the removal of plaque and calculus deposits. This is achieved through the use of specifically designed instruments for debridement of tooth surfaces. Treatment with these types of instruments is necessary as calculus deposits cannot be removed by brushing or flossing alone. To effectively manage disease or maintain oral health, thorough removal of calculus deposits should be completed at frequent intervals. The recommended frequency of dental hygiene treatment can be made by a registered professional, and is dependent on individual patient needs. Factors that are taken into consideration include an individual's overall health status, tobacco use, amount of calculus present, and adherence to a professionally recommended home care routine. Hand instruments are specially designed tools used by dental professionals to remove plaque and calculus deposits that have formed on the teeth. These tools include scalers, curettes, jaquettes, hoes, files and chisels. Each type of tool is designed to be used in specific areas of the mouth. Some commonly used instruments include sickle scalers which are designed with a pointed tip and are mainly used supragingivally. Curettes are mainly used to remove subgingival calculus, smooth root surfaces and to clean out periodontal pockets. Curettes can be divided into two subgroups: universals and area specific instruments. Universal curettes can be used in multiple areas, while area specific instruments are designed for select tooth surfaces. Gracey curettes are a popular type of area specific curettes. Due to their design, area specific curettes allow for better adaptation to the root surface and can be slightly more effective than universals. Hoes, chisels, and files are less widely used than scalers and curettes. These are beneficial when removing large amounts of calculus or tenacious calculus that cannot be removed with a curette or scaler alone. Chisels and hoes are used to remove bands of calculus, whereas files are used to crush burnished or tenacious calculus. Ultrasonic scalers, also known as power scalers, are effective in removing calculus, stain, and plaque. These scalers are also useful for root planing, curettage, and surgical debridement. Not only is tenacious calculus and stain removed more effectively with ultrasonic scalers than with hand instrumentation alone, it is evident that the most satisfactory clinical results are when ultrasonics are used in adjunct to hand instrumentation. There are two types of ultrasonic scalers; piezoelectric and magnetostrictive. Oscillating material in both of these handpieces cause the tip of the scaler to vibrate at high speeds, between 18,000 and 50,000 Hz. The tip of each scaler uses a different vibration pattern for removal of calculus. The magnetostrictive power scaler vibration is elliptical, activating all sides of the tip, whereas the piezoelectric vibration is linear and is more active on the two sides of the tip. Special tips for ultrasonic scalers are designed to address different areas of the mouth and varying amounts of calculus buildup. Larger tips are used for heavy subgingival or supragingival calculus deposits, whereas thinner tips are designed more for definitive subgingival debridement. As the high frequency vibrations loosen calculus and plaque, heat is generated at the tip. A water spray is directed towards the end of the tip to cool it as well as irrigate the gingiva during debridement. Only the first 1–2 mm of the tip on the ultrasonic scaler is most effective for removal, and therefore needs to come into direct contact with the calculus to fracture the deposits. Small adaptations are needed in order to keep the tip of the scaler touching the surface of the tooth, while overlapping oblique, horizontal, or vertical strokes are used for adequate calculus removal. Current research on potentially more effective methods of subgingival calculus removal focuses on the use of near-ultraviolet and near-infrared lasers, such as Er,Cr:YSGG lasers. The use of lasers in periodontal therapy offers a unique clinical advantage over conventional hand instrumentation, as the thin and flexible fibers can deliver laser energy into periodontal pockets that are otherwise difficult to access. Near-infrared lasers, such as the Er,CR:YSGG laser, have been proposed as an effective adjunct for calculus removal as the emission wavelength is highly absorbed by water, a large component of calculus deposits. An optimal output power setting of 1.0-W with the near-infrared Er,Cr:YSGG laser has been shown to be effective for root scaling. Near-ultraviolet lasers have also shown promise as they allow the dental professional to remove calculus deposits quickly, without removing underlying healthy tooth structure, which often occurs during hand instrumentation. Additionally, near-ultraviolet lasers are effective at various irradiation angles for calculus removal. Discrepancies in the efficiency of removal are due to the physical and optical properties of the calculus deposits, not to the angle of laser use. Dental hygienists must receive additional theoretical and clinical training on the use of lasers, where legislation permits.

References

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