cementum

セメント質 　 　

WordNet

1. a specialized bony substance covering the root of a tooth (同)cement
2. make fast as if with cement; "We cemented our friendship"
3. a building material that is a powder made of a mixture of calcined limestone and clay; used with water and sand or gravel to make concrete and mortar
4. any of various materials used by dentists to fill cavities in teeth
5. concrete pavement is sometimes referred to as cement; "they stood on the grey cement beside the pool"
6. something that hardens to act as adhesive material
7. bind or join with or as if with cement
8. cover or coat with cement

PrepTutorEJDIC

1. (歯の)セメント質
2. 『セメント』;接合剤,接着剤 / 結合,(友情の)きずな / …‘に'セメントを塗る,'を'セメントで固める / 〈友情・関係など〉'を'固める,堅く結び付ける / 結びつく,固まる

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/02/20 05:18:41」(JST)

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Cementum
The cementum is the surface layer of the tooth root. Rather than being a passive entity like paint on a wall, cementum is a dynamic entity within the periodontium. It is attached to the alveolar bone (C) by the fibers of the periodontal ligament and to the soft tissue of the gingiva by the gingival fibers (H).
Details
Identifiers
Latin	caementum
TA	A05.1.03.057 A03.1.03.007
FMA	55630
Anatomical terminology [edit on Wikidata]

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.

Development

Cementum is excreted by cells called cementoblasts within the root of the tooth and is thickest at the root apex. These cementoblasts develop from undifferentiated mesenchymal cells in the connective tissue of the dental follicle or sac.

Unlike ameloblasts and odontoblasts, which leave no cellular bodies in their secreted products, during the later steps within the stage of apposition, many of the cementoblasts become entrapped by the cementum they produce, becoming cementocytes. Thus again, cementum is more similar to alveolar bone, with its osteoblasts becoming entrapped osteocytes.

Cementum is capable of repairing itself to a limited degree and is not resorbed under normal conditions.

Features

Cementum is slightly softer than dentin and consists of about 45% to 50% inorganic material (hydroxylapatite) by weight and 50% to 55% organic matter and water by weight. The organic portion is composed primarily of collagen and proteoglycans. Cementum is avascular, receiving its nutrition through its own imbedded cells from the surrounding vascular periodontal ligament.

The cementum is light yellow and slightly lighter in color than dentin. It has the highest fluoride content of all mineralized tissue. Cementum also is permeable to a variety of materials. It is formed continuously throughout life because a new layer of cementum is deposited to keep the attachment intact as the superficial layer of cementum ages. Cementum on the root ends surrounds the apical foramen and may extend slightly onto the inner wall of the pulp canal.

Structure

The cells of cementum are the entrapped cementoblasts, the cementocytes. Each cementocyte lies in its lacuna (plural, lacunae), similar to the pattern noted in bone. These lacunae also have canaliculi or canals. Unlike those in bone, however, these canals in cementum do not contain nerves, nor do they radiate outward. Instead, the canals are oriented toward the periodontal ligament and contain cementocytic processes that exist to diffuse nutrients from the ligament because it is vascularized.

After the apposition of cementum in layers, the cementoblasts that do not become entrapped in cementum line up along the cemental surface along the length of the outer covering of the periodontal ligament. These cementoblasts can form subsequent layers of cementum if the tooth is injured.

Sharpey fibers are part of the principal collagenous fibers of the periodontal ligament embedded in the cementum and alveolar bone to attach the tooth to the alveolus.

Cementoenamel junction

Main article: Cementoenamel junction

The cementum joins the enamel to form the cementoenamel junction (CEJ), which is referred to as the cervical line.

Three possible types of transitional interfaces may be present at the CEJ. The traditional view was that certain interfaces dominated in certain oral cavities. The CEJ may exhibit all of these interfaces in an individual’s oral cavity, and there is even considerable variation when one tooth is traced circumferentially.

Dentinocemental junction

When the cementoid reaches the full thickness needed, the cementoid surrounding the cementocytes becomes mineralized, or matured, and is then considered cementum. Because of the apposition of cementum over the dentin, the dentinocemental junction (DCJ) is formed. This interface is not as defined, either clinically or histologically, as that of the dentinoenamel junction (DEJ), given that cementum and dentin are of common embryological background, unlike that of enamel and dentin.

The dentinocemental junction (DCJ) is a relatively smooth area in the permanent tooth, and attachment of cementum to the dentin is firm but not understood completely.

Types

Two kinds of cementum are formed: acellular and cellular, and fibers can be intrinsic or extrinsic, resulting in four possible permutations; the first cementum to be formed during tooth development is acellular extrinsic fiber cementum. The acellular layer of cementum is living tissue that does not incorporate cells into its structure and usually predominates on the coronal half of the root; cellular cementum occurs more frequently on the apical half.

Pathology

• Some root resorption of the apical portion of the root may occur, however, if orthodontic pressures are excessive and movement is too fast. Some experts also agree on a third type of cementum, afibrillar cementum, which sometimes extends onto the enamel of the tooth.
• The excessive buildup of cementum on the roots of a tooth is a pathological condition known as hypercementosis. Cementum thickness can increase on the root end to compensate for attritional wear of the occlusal/incisal surface and passive eruption of the tooth.
• When cementum is exposed through gingival recession, it quickly undergoes abrasion by mechanical friction because of its low mineral content and thinness. The exposure of the deeper dentin can lead to problems such as extrinsic staining and dentinal hypersensitivity.
• The incidence of cemental caries increases in older adults as gingival decline occurs from either trauma or periodontal illness. It is a chronic condition that forms a large, shallow lesion and slowly invades first the root’s cementum and then dentin to cause a chronic infection of the pulp. Because dental pain is a late finding, many lesions are not detected early, resulting in restorative obstacles and increased tooth loss.
• Cementicles are small, spherical or ovoid calcified masses embedded within or attached to the cementum layer on the root surface of a tooth, or lying free within the periodontal ligament.
• Cemental spurs can be found at or near the CEJ. These are symmetrical spheres of cementum attached to the cemental root surface, similar to enamel pearls. Cemental spurs result from irregular deposition of cementum on the root. They can present some clinical problems in differentiation from calculus and may be noted on radiographs; yet, because they are hard dental tissue, they are not easily removed, and thus may also interfere with periodontal treatment.

DNA studies

A 2010 archeological study has found that cementum has five times the amount of mitochondrial DNA compared to dentin, which is commonly sampled. Teeth are increasingly utilized as a source of nuclear DNA to aid identification of human remains. DNA extraction and the results of genetic analysis from the tissue are extremely variable and to some extent unpredictable. However, the quantity of DNA available in dentin is affected by age and dental disease, whereas that in cementum is not.

See also

• Tooth development
• Dentin
• Periodontal ligament
• Periodontium
• Cementoma
• Hypercementosis

References

External links

1. Cementum, Max A. Listgarten, University of Pennsylvania and Temple University at http://www.dental.pitt.edu/informatics/periohistology/en/gu0501.htm
2. Harvesting cementum from root surface: A new paradigm in the study of cementum and the cemento-dentinal junction, George Cherian, Journal of Academy of Advanced Dental Research, Vol 2; Issue 2: May 2011 at http://www.joaor.org/userfiles/Vol-2-Issue-2-May-Aug-2011/03George.pdf
3. Survival and recovery of DNA from ancient teeth and bones at http://www.icb.ufmg.br/labs/lbem/pdf/AdlerJ_Archae_Sci_(2011)_38(5)_956-964.pdf

UpToDate Contents

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• 1. 歯の解剖学的構造および発達 anatomy and development of the teeth
• 2. 歯性感染症の疫学、病因、および臨床症状 epidemiology pathogenesis and clinical manifestations of odontogenic infections
• 3. 小児における歯周病関連の全身疾患 systemic conditions associated with periodontal disease in children
• 4. 成人における歯肉炎および歯周炎：分類と歯科治療 gingivitis and periodontitis in adults classification and dental treatment
• 5. 歯の発達障害 developmental defects of the teeth

English Journal

• Ameloblastin modulates osteoclastogenesis through the integrin/ERK pathway.

• Lu X, Ito Y, Atsawasuwan P, Dangaria S, Yan X, Wu T, Evans CA, Luan X.SourceUniversity of Illinois College of Dentistry, Brodie Laboratory for Craniofacial Genetics, Department of Oral Biology.
• Bone.Bone.2013 Feb 2. pii: S8756-3282(13)00058-6. doi: 10.1016/j.bone.2013.01.041. [Epub ahead of print]
• Proteins of the extracellular matrix often have multiple functions to facilitate complex tasks ranging from signaling to structural support. Here we have focused on the function of one of the matrix proteins expressed in bones and teeth, the matrix adhesion protein ameloblastin (AMBN). Transgenic mi
• PMID 23385480

• Assessing the application of tooth cementum annulation relative to macroscopic aging techniques in an archeological sample.

• Gauthier J, Schutkowski H.SourceDepartment of Anthropology, University of Wyoming, Laramie, WY 82070, USA.
• Homo : internationale Zeitschrift für die vergleichende Forschung am Menschen.Homo.2013 Feb;64(1):42-57. doi: 10.1016/j.jchb.2012.11.001. Epub 2012 Dec 6.
• The analysis of human skeletal remains is frequently impeded by the lack of adequately preserved morphological markers on which to base age estimation, particularly in archeological contexts. Therefore, histological methods such as tooth cementum annulation analysis can be useful for extracting reli
• PMID 23218650

• Tooth root dentin mineralization defects in a mouse model of hypophosphatasia.

• Foster B, Nagatomo K, Tso H, Tran A, Nociti F Jr, Narisawa S, Yadav M, McKee M, Millán J, Somerman M.SourceNational Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), National Institutes of Health (NIH), Bethesda, MD, USA. brian.foster@nih.gov.
• Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research.J Bone Miner Res.2013 Feb;28(2):271-82. doi: 10.1002/jbmr.1767.
• Tissue-nonspecific alkaline phosphatase (TNAP) is expressed in mineralizing tissues and functions to reduce pyrophosphate (PP(i) ), a potent inhibitor of mineralization. Loss of TNAP function causes hypophosphatasia (HPP), a heritable disorder marked by increased PP(i) , resulting in rickets and ost
• PMID 22991301

Japanese Journal

• <b>Caspase-mediated Apoptosis by Compressive Force Induces RANKL in Cementoblasts </b>

• International Journal of Oral-Medical Sciences 16(2), 31-38, 2018
• NAID 130006320938

• Transplantation of mature adipocyte-derived dedifferentiated fat cells into three-wall defects in the rat periodontium induces tissue regeneration

• Ｊｏｕｒｎａｌ　ｏｆ　Ｏｒａｌ　Ｓｃｉｅｎｃｅ 59(4), 611-620, 2017
• NAID 130006286520

• 両側上顎洞に多発性に生じた集合性歯牙腫の1例

• 日本口腔外科学会雑誌 63(8), 394-398, 2017
• NAID 130006176507

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リンク元	「セメント質」
拡張検索	「dental cementum」
関連記事	「cement」

「セメント質」

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英

cement (Z), cementum

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「dental cementum」

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cementoblast、cementum

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• セメント、充填材、接合剤

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sealant