Editing Human tooth (section)

==Supporting structures==
[[File:Eruptingtoothwithlabels11-24-05.jpg|thumb|Histologic slide of tooth erupting into the mouth <br />A: tooth <br />B: gingiva
<br />C: bone
<br />D: periodontal ligaments]]

The [[periodontium]] is the supporting structure of a tooth, helping to attach the tooth to surrounding tissues and to allow sensations of touch and pressure.<ref name = "ross452"/> It consists of the cementum, periodontal ligaments, [[alveolar bone]], and [[gingiva]]. Of these, cementum is the only one that is a part of a tooth. Periodontal ligaments connect the alveolar bone to the cementum. Alveolar bone surrounds the roots of teeth to provide support and creates what is commonly called an [[Dental alveolus|alveolus]], or "socket". Lying over the bone is the [[gingiva]] or gum, which is readily visible in the mouth.

===Periodontal ligaments===
The [[periodontal ligament]] is a specialized [[connective tissue]] that attaches the cementum of a tooth to the alveolar bone. This tissue covers the root of the tooth within the bone. Each ligament has a width of 0.15–0.38mm, but this size decreases over time.<ref name="Cate256">{{harvnb|Cate|1998|page=256}}</ref> The functions of the periodontal ligaments include attachment of the tooth to the bone, support for the tooth, formation and [[Bone resorption|resorption]] of bone during tooth movement, sensation, and eruption.<ref name = "ross453"/> The cells of the periodontal ligaments include osteoblasts, osteoclasts, fibroblasts, macrophages, cementoblasts, and [[epithelial cell rests of Malassez]].<ref name="Cate260">{{harvnb|Cate|1998|page=260}}</ref> Consisting of mostly Type I and III [[collagen]], the fibers are grouped in bundles and named according to their location. The groups of fibers are named alveolar crest, horizontal, oblique, periapical, and interradicular fibers.<ref>Listgarten, Max A. "[https://web.archive.org/web/20130520224440/http://www.dental.pitt.edu/informatics/periohistology/en/gu0404.htm Histology of the Periodontium: Principal fibers of the periodontal ligament]," University of Pennsylvania and Temple University. Created May 8, 1999, revised 16 January 2007.</ref> The nerve supply generally enters from the bone apical to the tooth and forms a network around the tooth toward the crest of the gingiva.<ref name="Cate270">{{harvnb|Cate|1998|page=270}}</ref> When pressure is exerted on a tooth, such as during chewing or biting, the tooth moves slightly in its socket and puts tension on the periodontal ligaments. The nerve fibers can then send the information to the central nervous system for interpretation.

===Alveolar bone===
The [[alveolar bone]] is the bone of the jaw which forms the alveolus around teeth.<ref name="Cate274">{{harvnb|Cate|1998|page=274}}</ref> Like any other bone in the human body, alveolar bone is modified throughout life. [[Osteoblast]]s create bone and [[osteoclast]]s destroy it, especially if force is placed on a tooth.<ref name="ross452">{{harvnb|Ross|2002|page=452}}</ref> As is the case when movement of teeth is attempted through orthodontics, an area of bone under [[compression (physical)|compressive]] [[force]] from a tooth moving toward it has a high osteoclast level, resulting in [[bone resorption]]. An area of bone receiving [[tension (mechanics)|tension]] from periodontal ligaments attached to a tooth moving away from it has a high number of osteoblasts, resulting in bone formation.

===Gingiva===
The [[gingiva]] ("gums") is the [[mucous membranes|mucosal]] tissue that overlays the jaws. There are three different types of epithelium associated with the gingiva: gingival, junctional, and sulcular epithelium. These three types form from a mass of epithelial cells known as the epithelial cuff between the tooth and the mouth.<ref name="Cate247and248">{{harvnb|Cate|1998|pages=247 and 248}}</ref> The gingival epithelium is not associated directly with tooth attachment and is visible in the mouth. The junctional epithelium, composed of the [[basal lamina]] and [[hemidesmosome]]s, forms an attachment to the tooth.<ref name="ross453"/> The sulcular epithelium is [[Epidermis (skin)|nonkeratinized]] [[Squamous epithelium|stratified squamous]] tissue on the gingiva which touches but is not attached to the tooth.<ref name="Cate280">{{harvnb|Cate|1998|page=280}}</ref>