Editing Human tooth (section)

===Dentin===
{{Main|Dentin}}

Dentin is the substance between enamel or cementum and the pulp chamber. It is secreted by the [[odontoblast]]s of the dental pulp.<ref name = "ross448"/> The formation of dentin is known as [[dentinogenesis]]. The porous, yellow-hued material is made up of 70% inorganic materials, 20% organic materials, and 10% water by weight.<ref name = "Cate150"/> Because it is softer than enamel, it decays more rapidly and is subject to severe cavities if not properly treated, but dentin still acts as a protective layer and supports the crown of the tooth.

Dentin is a mineralized [[connective tissue]] with an organic matrix of collagenous proteins. Dentin has microscopic channels, called dentinal tubules, which radiate outward through the dentin from the pulp cavity to the exterior cementum or enamel border.<ref name="ross450">{{harvnb|Ross|2002|page=450}}</ref> The diameter of these tubules range from 2.5 μm near the pulp, to 1.2 μm in the midportion, and 900&nbsp;nm near the dentino-enamel junction.<ref name="Cate152">{{harvnb|Cate|1998|page=152}}</ref> Although they may have tiny side-branches, the tubules do not intersect with each other. Their length is dictated by the radius of the tooth. The three dimensional configuration of the dentinal tubules is genetically determined.

There are three types of dentin, primary, secondary and tertiary.<ref>{{Cite journal |title=Sex- and Age-related Differences in Primary and Secondary Dentin Formation |journal = Advances in Dental Research |volume = 15 |pages = 42–45 |doi=10.1177/08959374010150011101 |pmid = 12640738 |year = 2001 |last1 = Zilberman |first1 = U. |last2 = Smith |first2 = P. |citeseerx = 10.1.1.535.5123|s2cid = 4798656 }}</ref> Secondary dentin is a layer of dentin produced after root formation and continues to form with age. [[Tertiary dentin]] is created in response to stimulus, such as [[Tooth decay|cavities]] and [[tooth wear]].<ref>{{Cite web|url=https://www.researchgate.net/publication/331906742|title=Tertiary Dentine Frequencies in Extant Great Apes and Fossil Hominins|website=ResearchGate|language=en|access-date=2019-03-28}}</ref>