What is Dentin?
[[File:Dentin (PSF).png|thumb|right|150px|{{Center|Drawing showing dentin}}]] '''Dentin''' or '''dentine''' is [[Calcification|calcified]] [[Tissue (biology)|tissue]] that makes up the second layer of [[teeth]]. In the crown (top) of a tooth, dentin is found between [[Tooth enamel|enamel]] and [[Dental pulp|pulp]]. In the root of a tooth, it is found between [[cementum]] and pulp. Dentin makes up most of a tooth.<ref>Nanci, Antonio (2013). Ten Cate's Oral Histology: Development, Structure, and Function. 8th ed. St. Louis, MO: Elsevier, 2013. 165. print.</ref> Dentin is [[yellow]]. The yellowness of dentin shows through in a tooth because enamel is [[transparent|semi-translucent]]. == Composition == Dentin is made up of * 70% [[apatite|hydroxylapatite]]<ref name=Omelyanenko457>Omelyanenko, Nikolay, Leonid Slutsky, and S. P. Mironov. Connective Tissue: Histophysiology, Biochemistry, Molecular Biology. Boca Raton: CRC, 2014. 457. print</ref> (a [[mineral]] found in teeth and [[bone]]s) * 20% [[organic matter]]<ref name=Omelyanenko457/> (matter that comes from living things) * 10% water<ref name=Omelyanenko457/> == Development == The process of creating dentin is called '''dentinogenesis'''. It is made by [[odontoblast]]s, a special type of [[cell]] that activates later during [[wikt:formation|formation]] of teeth. Unlike enamel, a tooth can keep making more dentin throughout life. == Types == Dentin is divided into different types based on when it is made. === Primary dentin === Primary dentin makes up most of the tooth. It is the thick bulk between enamel and pulp. Primary dentin is the type of dentin a tooth starts out with. It can also be called circumpulpal (surrounding the pulp) dentin. Mantle dentin is a separate, harder but thinner layer that separates primary dentin from the tooth crown. === Secondary dentin === Secondary dentin is made after a tooth has already appeared in the [[mouth]]. This type of dentin is made throughout life. Newly made dentin is found placed very close to the pulp. It is fo