Editing Human tooth (section)

===Cementum===
{{Main|Cementum}}

Cementum is a specialized bone like substance covering the root of a tooth.<ref name = "ross448"/> It is approximately 45% inorganic material (mainly [[hydroxyapatite]]), 33% organic material (mainly [[collagen]]) and 22% water. Cementum is excreted by [[cementoblast]]s within the root of the tooth and is thickest at the [[Root apex (dental)|root apex]]. Its coloration is yellowish and it is softer than dentin and enamel. The principal role of cementum is to serve as a medium by which the [[periodontal ligament]]s can attach to the tooth for stability. At the cement to enamel junction, the cementum is acellular due to its lack of cellular components, and this acellular type covers at least {{frac|2|3}} of the root.<ref name="Cate236">{{harvnb|Cate|1998|page=236}}</ref> The more permeable form of cementum, cellular cementum, covers about {{frac|1|3}} of the root apex.<ref name="Cate241">{{harvnb|Cate|1998|page=241}}</ref>