Editing Tooth enamel (section)

== Features ==
Enamel is the hardest substance in the human body and contains the highest percentage of minerals (at 96%),<ref name="ross485">Ross ''et al.'', p. 485</ref> with water and organic material composing the rest.<ref name=":4">Ten Cate's Oral Histology, Nancy, Elsevier, pp. 70–94</ref> The primary mineral is [[hydroxyapatite]], which is a [[crystal]]line [[calcium phosphate]].<ref name="staines" /> Enamel is formed on the tooth while the tooth develops within the jaw bone before it [[Tooth eruption|erupts]] into the mouth. Once fully formed, enamel does not contain blood vessels or nerves, and is not made of cells. [[Remineralisation of teeth]] can repair damage to the tooth to a certain degree but damage beyond that cannot be repaired by the body.  The maintenance and repair of human tooth enamel is one of the primary concerns of [[dentistry]].

In humans, enamel varies in thickness over the surface of the tooth, often thickest at the [[Cusp (dentistry)|cusp]], up to 2.5&nbsp;mm, and thinnest at its border with the [[cementum]] at the [[cementoenamel junction]] (CEJ).<ref name="cate219">Ten Cate's Oral Histology, Nanci, Elsevier, 2013, p. 122</ref>

The normal color of enamel varies from light yellow to grayish (bluish) white. It has been suggested that the color is determined by differences in the translucency of enamel, yellowish teeth having a thin, translucent enamel through which the yellow color of the dentin is visible and grayish teeth having a more opaque enamel. The translucency may be attributable to variations in the degree of calcification and homogeneity of the enamel. At the edges of teeth where there is no dentin underlying the enamel, the color sometimes has a slightly blue or translucent off-white tone, easily observable on the [[upper incisors]]. Since enamel is [[translucent|semitranslucent]], the color of dentin and any material underneath the enamel strongly affects the [[Human physical appearance|appearance]] of a tooth. The enamel on primary teeth has a more opaque crystalline form and thus appears whiter than on permanent teeth.

<!-- article quote "Enamel is a composite material, consisting of about 87 vol% mineral, nominally hydroxyapatite, Ca5(PO4)3OH, 2% organic component, and 11% water" -->The large amount of mineral in enamel accounts not only for its strength but also for its brittleness.<ref name=":3">Ten Cate's Oral Histology, Nanci, Elsevier, pp. 70–94</ref> Tooth enamel ranks 5 on [[Mohs scale of mineral hardness|Mohs hardness scale]] (between steel and titanium) and has a [[Young's modulus]] of 83 GPa.<ref name="staines">{{cite journal|journal=Journal of Materials Science|year=1981|title=Spherical indentation of tooth enamel|author=M. Staines, W. H. Robinson and J. A. A. Hood| doi = 10.1007/bf01113595 | volume=16 |issue =9 | pages= 2551–2556 |bibcode=1981JMatS..16.2551S|s2cid=137704231}}</ref> Dentin, less mineralized and less brittle, 3–4 in hardness, compensates for enamel and is necessary as a support.<ref name="johnson">Johnson</ref> On radiographs, the differences in the mineralization of different portions of the tooth and surrounding periodontium can be noted; enamel appears lighter than dentin or pulp since it is denser than both and more [[Radiodensity|radiopaque]].<ref name=":0">Fehrenbach, MJ and Popowics, T. (2026). ''Illustrated Dental Embryology, Histology, and Anatomy'', 6th edition, Elsevier, p. 164.</ref>

Enamel does not contain [[collagen]], as found in other hard tissues such as dentin and [[bone]], but it does contain two unique classes of [[protein]]s: [[amelogenin]]s and [[enamelin]]s. While the role of these proteins is not fully understood, it is believed that they aid in the development of enamel by serving as a framework for minerals to form on, among other functions.<ref name=":3" /> Once it is mature, enamel is almost totally without the softer organic matter. Enamel is avascular and has no nerve supply within it and is not renewed, however, it is not a static tissue as it can undergo mineralization changes.<ref>Fehrenbach, Popowics, p. 168</ref>