What is Cementum?
'''Cementum''' is the hard [[wikt:outside|outside]] [[wikt:layer|layer]] of a [[teeth|tooth]] root.<ref name=Nanci205>Nanci, Antonio. Ten Cate's Oral Histology: Development, Structure, and Function. 8th ed. St. Louis, MO: Mosby Elsevier,: Elsevier, 2013. 205-18. Print.</ref> It is not present in the crown (part above the [[gums]]) portion of a tooth. Cementum allows [[periodontal ligament]]s to attach onto it, allowing tooth to be [[Connection|connected]] to the [[maxilla]] or [[mandible]]. == Composition == Cementum is made up of * 45% to 50% [[apatite|hydroxyapatite]]<ref name=Nanci205/> (mineral found in teeth and [[bones]]) * 50% to 55% [[collagen]]<ref name=Nanci205/> (mostly Type I collagen) and non-collagen [[organic matter]] == Development == The process of [[creating]] cementum is called '''cementogenesis'''.<ref>Ireland, Robert. A Dictionary of Dentistry. Oxford: Oxford University Press, 2010. 69. Internet resource.</ref> It is made by special type of [[cells]] known as cementoblasts.<ref name=Nanci205/> Cementoblasts are found on the [[surface]] of the cementum. When a cementoblast is no longer on the surface, or when it is found surrounded by cementum, it is then known as a cementocyte. In contrast, cementoclasts are special cells that remove cementum instead of making cementum. == Cementoenamel junction == The cementoenamel junction, or the cervical line, is the where [[Tooth enamel|enamel]] and cementum meet. The cementum and enamel may meet in different ways. * As a butt joint: This is when the enamel meets and touches the cementum. * With a gap: The enamel and cementum do not meet and touch. The gap they leave exposes [[dentin]] underneath. * Overlapping: Cementum overlaps over the enamel. == Types == Cementum can be divided into two main types based on its location and whether it has cells or not. *'''Acellular cementum'''.<ref name=Chandra15>Chandra, Satish, Shaleen Chandra, and Girish Chandra. Textbook of Operative Dentistry (with Mcqs). New Delhi: Jaypee Brothers Medical Publishers L