WordNet

a calcareous material harder and denser than bone that comprises the bulk of a tooth (同)dentin
bone (calcified tissue) surrounding the pulp cavity of a tooth (同)dentin
an appreciable consequence (especially a lessening); "it made a dent in my bank account"
an impression in a surface (as made by a blow) (同)ding, gouge, nick

PrepTutorEJDIC

(通例エナメル質の下にある)ぞうげ質
くぼみ,へこみ / …‘を'くぼませる,へこませる / へこむ,くぼむ
(くし・歯車などの)歯

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/03/15 17:34:38」(JST)

wiki en

Parts of a tooth, including dentine

Dentine (British English: dentine, American English: dentin, Latin: substantia eburnea) is a calcified tissue of the body, and along with enamel, cementum, and pulp is one of the four major components of teeth. Usually, it is covered by enamel on the crown and cementum on the root and surrounds the entire pulp. By weight, seventy percent of dentin consists of the mineral hydroxylapatite, twenty percent is organic material and ten percent is water.^[1] Yellow in appearance, it greatly affects the color of a tooth due to the translucency of enamel. Dentin, which is less mineralized and less brittle than enamel, is necessary for the support of enamel.^[2]

Dentin consists of microscopic channels, called dentinal tubules, which radiate outward through the dentin from the pulp to the exterior cementum or enamel border.^[3] These tubules contain fluid and cellular structures. As a result, dentin has a degree of permeability which can increase the sensation of pain and the rate of tooth decay.

The formation of dentin, known as dentinogenesis, begins prior to the formation of enamel and is initiated by the odontoblasts of the pulp. Unlike enamel, dentin continues to form throughout life and can be initiated in response to stimuli, such as tooth decay or attrition.

Structure

Dentin is bone-like matrix characterized by multiple closely packed dentinal tubules that traverse its entire thickness and contain the cytoplasmic extensions of odontoblasts that once formed the dentine and maintain it. The cell bodies of the odontoblasts are aligned along the inner aspect of dentine against a layer of predentine where they also form the peripheral boundary of the dental pulp.

Types

There are three types of dentin, primary, secondary and tertiary.^[4]^[5] Primary dentin is the outermost layer of dentin and borders the enamel. Secondary dentin is a layer of dentin produced after the root of the tooth is completely formed. Tertiary dentin is created in response to a stimulus, such as a carious attack.

Primary dentin

Primary dentin, the most prominent dentin in the tooth, lies between the enamel and the pulp chamber. The outer layer closest to enamel is known as mantle dentin. This layer is unique to the rest of primary dentin. Mantle dentin is formed by newly differentiated odontoblasts and forms a layer approximately 150 micrometers wide. Unlike primary dentin, mantle dentin lacks phosphoryn, has loosely packed collagen fibrils and is less mineralized. Below it lies the circumpulpal dentin, a more mineralized dentin which makes up most of the dentin layer and is secreted after the mantle dentin by the odontoblasts. Circumpulpal dentin is formed before the root formation is completed.

Newly secreted dentin is unmineralised and is called predentin. It is easily identified in haematoxylin and eosin stained sections since it stains less intensely than dentin. It is usually 10-47 micrometer and lines the innermost region of the dentin. It is unmineralized and consists of collagen, glycoproteins and proteoglycans. It is similar to osteoid in bone and is thickest when dentinogenesis is occurring.

Secondary dentin (Regular Secondary Dentin)

Secondary dentin is formed after root formation is complete, normally after the tooth has erupted and is functional. It grows much more slowly than primary dentin, but maintains its incremental aspect of growth. It has a similar structure to primary dentin, although its deposition is not always even around the pulp chamber. It is the growth of this dentin that causes the decrease in the size of the pulp chamber with age. This is clinically known as pulp recession; cavity preparation in young patients therefore carries a greater risk of exposing the pulp. If this occurs, the pulp can be treated by different therapies such as direct pulp capping. Pulp capping is most successful if followed by a stainless steel crown. Attempts are made not to extract a pulpal exposure as to maintain space in the primary dentition.

Tertiary dentin (Irregular Secondary Dentin or Reparative Dentin or Sclerotic Dentin) - pathologic

Tertiary dentin is dentin formed as a reaction to external stimulation such as cavities. It is of two types, either reactionary, where dentin is formed from a pre-existing odontoblast, or reparative, where newly differented odontoblast-like cells are formed due to the death of the original odontoblasts, from a pulpal progenitor cell. Tertiary dentin is only formed by an odontoblast directly affected by a stimulus; therefore, the architecture and structure depend on the intensity and duration of the stimulus, e.g., if the stimulus is a carious lesion, there is extensive destruction of dentin and damage to the pulp, due to the differentiation of bacterial metabolites and toxins. Thus, tertiary dentin is deposited rapidly, with a sparse and irregular tubular pattern and some cellular inclusions; in this case it is referred to as "osteodentin". However, if the stimulus is less active, it is laid down less rapidly with a more regular tubular pattern and hardly any cellular inclusions.

Elephant ivory is solid dentin. The structure of the dentinal tubules contributes to both its porosity (useful for piano keys) and its elasticity (useful for billiard balls.) Elephant tusks are formed with a thin cap of enamel, which soon wears away, leaving the dentin exposed. Exposed dentin in humans causes the symptom of sensitive teeth.

Because dentin is softer than enamel, it wears away more quickly than enamel. Some mammalian teeth exploit this phenomenon, especially herbivores such as horses, deer or elephants. In many herbivores, the occlusal (biting) surface of the tooth is composed of alternating areas of dentin and enamel. Differential wearing causes sharp ridges of enamel to be formed on the surface of the tooth (typically a molar), and to remain during the working life of the tooth. Herbivores grind their molars together as they chew (masticate), and the ridges help to shred tough plant material.

Unlike enamel, dentin may be demineralized and stained for histological study. Dentin rates approximately 3 on the Mohs scale of mineral hardness.

A material similar to dentin forms the hard material that makes up dermal denticles in sharks and other cartilaginous fish.

References

^ Cate, A.R. Ten. Oral Histology: development, structure, and function. 5th ed. 1998. Page 150. ISBN 0-8151-2952-1.
^ Johnson, Clarke. "Biology of the Human Dentition." Page accessed July 18, 2007.
^ Ross, Michael H., Gordon I. Kaye, and Wojciech Pawlina, 2003. Histology: a text and atlas. 4th edition. Page 450. ISBN 0-683-30242-6.
^ U. Zilberman, P. Smith. Sex- and Age-related Differences in Primary and Secondary Dentin Formation Advances in Dental Research, Vol 15, Issue 1, pp.42-45, August, 2001. Retrieved from iadrjournals.org
^ Donna J. Phinney, Judy Helen Halstead Delmar's Dental Assisting: A Comprehensive Approach, p.97, Thomson Delmar Learning, ISBN 0-7668-0731-2

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. 歯の発達障害 developmental defects of the teeth
2. 歯の解剖学的構造および発達 anatomy and development of the teeth
3. 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
4. 小児における歯の損傷の評価およびマネージメント evaluation and management of dental injuries in children
5. 遺伝性低リン血症性くる病と腫瘍誘発性骨軟化症 hereditary hypophosphatemic rickets and tumor induced osteomalacia

English Journal

Osteocytes serve as a progenitor cell of osteosarcoma.

Sottnik JL1, Campbell B, Mehra R, Behbahani-Nejad O, Hall CL, Keller ET.
Journal of cellular biochemistry.J Cell Biochem.2014 Aug;115(8):1420-9. doi: 10.1002/jcb.24793.
Osteosarcoma (OSA) is the most common primary bone tumor in humans. However, the cell of origin of OSA is not clearly defined although there is evidence that osteoblasts may serve as OSA progenitors. The role of osteocytes, terminally differentiated osteoblasts, as OSA progenitors has yet to be desc
PMID 24700678

On the deformation behavior of human dentin under compression and bending.

Zaytsev D1, Ivashov AS2, Mandra JV2, Panfilov P3.
Materials science & engineering. C, Materials for biological applications.Mater Sci Eng C Mater Biol Appl.2014 Aug 1;41:83-90. doi: 10.1016/j.msec.2014.04.046. Epub 2014 Apr 26.
The cause of difference in deformation behavior of human dentin under compression and bending is discussed. Mechanical properties of dentin under these deformation schemes are compared. Microstructural study of fracture surfaces of samples and cracks in dentin is carried out, too. Dentin behaves lik
PMID 24907741

Fracture analysis for biological materials with an expanded cohesive zone model.

An B1, Zhao X1, Arola D2, Zhang D3.
Journal of biomechanics.J Biomech.2014 Jul 18;47(10):2244-8. doi: 10.1016/j.jbiomech.2014.04.054. Epub 2014 May 14.
In this study, a theoretical framework for simulation of fracture of bone and bone-like materials is provided. An expanded cohesive zone model with thermodynamically consistent framework has been proposed and used to investigate the crack growth resistance of bone and bone-like materials. The revers
PMID 24877880

Japanese Journal

X-ray diffraction analysis of three-dimensional self-reinforcing monomer and its chemical interaction with tooth and hydroxyapatite

YOSHIDA Yasuhiro,YOSHIHARA Kumiko,NAGAOKA Noriyuki,HANABUSA Masao,MATSUMOTO Takuya,MOMOI Yasuko
Dental materials journal 31(4), 697-702, 2012-07-01
NAID 10030502018

Effect of air-drying dentin surfaces on dentin bond strength of a solvent-free one-step adhesive

TAKAI Tomoyuki,HOSAKA Keiichi,KAMBARA Keisuke,THITTHAWEERAT Suppason,MATSUI Naoko,TAKAHASHI Masahiro,KISHIKAWA Ryuzo,NAKAJIMA Masatoshi,OTSUKI Masayuki,FOXTON Richard M.,TAGAMI Junji
Dental materials journal 31(4), 558-563, 2012-07-01
NAID 10030501498

Related Pictures

★リンクテーブル★

リンク元	「象牙質」「dentine」「dentinal」
拡張検索	「hereditary opalescent dentin」「dentin sensitivity」「dentinogenesis imperfecta」「hereditary dentin hypoplasia」
関連記事	「dent」

「象牙質」

　　[★]

英: dentine (Z), dentin
同: ゾウゲ質

[show details]

ゾウゲ質 : 約 914 件
象牙質 : 約 204,000 件

「dentine」

　　[★]

象牙質

関: dentin、dentinal

「dentinal」

　　[★]

象牙質の

関: dentin、dentine

「hereditary opalescent dentin」

　　[★] 遺伝性象牙質形成不全症。遺伝性乳白色象牙質

「dentin sensitivity」

　　[★]

象牙質知覚過敏症、象牙質知覚過敏

「dentinogenesis imperfecta」

　　[★] 遺伝性象牙質形成不全症

「hereditary dentin hypoplasia」