Editing Temporomandibular joint dysfunction (section)

===Anatomy and physiology===

====Temporomandibular joints====
{{main|Temporomandibular joint}}
The temporomandibular joints are the dual articulation of the mandible with the skull. Each TMJ is classed as a "ginglymoarthrodial" joint since it is both a [[ginglymus]] (hinging joint) and an [[arthrodial joint|arthrodial]] (sliding) joint,<ref name="Alomar 2007">{{cite journal | vauthors = Alomar X, Medrano J, Cabratosa J, Clavero JA, Lorente M, Serra I, Monill JM, Salvador A | display-authors = 6 | title = Anatomy of the temporomandibular joint | journal = Seminars in Ultrasound, CT and MRI | volume = 28 | issue = 3 | pages = 170–83 | date = June 2007 | pmid = 17571700 | doi = 10.1053/j.sult.2007.02.002 }}</ref> and involves the condylar process of the mandible below, and the articular fossa (or glenoid fossa) of the [[temporal bone]] above. Between these articular surfaces is the articular disc (or meniscus), which is a biconcave, transversely oval disc composed of dense fibrous connective tissue. Each TMJ is covered by a fibrous capsule. There are tight fibers connecting the mandible to the disc, and loose fibers which connect the disc to the temporal bone, meaning there are in effect 2 joint capsules, creating an upper joint space and a lower joint space, with the articular disc in between.<!-- <ref name="Standring 2006" /> --> The [[synovial membrane]] of the TMJ lines the inside of the fibrous capsule apart from the articular surfaces and the disc. This membrane secretes [[synovial fluid]], which is both a lubricant to fill the joint spaces, and a means to convey nutrients to the tissues inside the joint. Behind the disc is loose vascular tissue termed the "bilaminar region" which serves as a posterior attachment for the disc and also fills with blood to fill the space created when the head of the condyle translates down the articular eminence.<ref name="Standring 2006">{{cite book |veditors=Standring S |title=Gray's anatomy : the anatomical basis of clinical practice |url=https://archive.org/details/graysanatomyanat0000unse |url-access=registration |year=2006 |publisher=Elsevier Churchill Livingstone |location=Edinburgh |isbn=978-0-443-07168-3 |edition=39th}}</ref> Due to its concave shape, sometimes the articular disc is described as having an anterior band, intermediate zone and a posterior band.<ref name="Davies 2001">{{cite journal | vauthors = Davies S, Gray RM | s2cid = 29993073 | title = What is occlusion? | journal = British Dental Journal | volume = 191 | issue = 5 | pages = 235–8, 241–5 | date = September 2001 | pmid = 11575759 | doi = 10.1038/sj.bdj.4801151a }}</ref> When the mouth is opened, the initial movement of the mandibular condyle is rotational, and this involves mainly the lower joint space, and when the mouth is opened further, the movement of the condyle is translational, involving mainly the upper joint space.<ref name="Som 2011">{{cite book |veditors=Som PM, Curtin HD |title=Head and neck imaging |year=2011 |publisher=Mosby Elsevier |location=St. Louis |isbn=978-0-323-05355-6 |edition=5th |vauthors=Westesson PL, Otonari-Yamamoto M, Sano T, Okano T |chapter=Anatomy, Pathology, and Imaging of the Temporomandibular Joint |chapter-url=http://www.expertconsultbook.com/expertconsult/ob/book.do?method=display&type=bookPage&decorator=none&eid=4-u1.0-B978-0-323-05355-6..00026-4&isbn=978-0-323-05355-6 |access-date=1 May 2014 |archive-date=2 May 2014 |archive-url=https://web.archive.org/web/20140502032820/http://www.expertconsultbook.com/expertconsult/ob/book.do?method=display&type=bookPage&decorator=none&eid=4-u1.0-B978-0-323-05355-6..00026-4&isbn=978-0-323-05355-6 |url-status=dead }}</ref> This translation movement is achieved by the condylar head sliding down the articular eminence, which constitutes the front border of the articular fossa.<ref name="Kerawala 2010" /> The function of the articular eminence is to limit the forwards movement of the condyle.<ref name="Kerawala 2010" /> The ligament directly associated with the TMJ is the [[temporomandibular ligament]], also termed the lateral ligament, which really is a thickening of the lateral aspect of the fibrous capsule.<ref name="Kerawala 2010" /> The [[stylomandibular ligament]] and the [[sphenomandibular ligament]] are not directly associated with the joint capsule. Together, these ligaments act to restrict the extreme movements of the joint.<ref name="Cuccia 2011">{{cite journal | vauthors = Cuccia AM, Caradonna C, Caradonna D | title = Manual therapy of the mandibular accessory ligaments for the management of temporomandibular joint disorders | journal = The Journal of the American Osteopathic Association | volume = 111 | issue = 2 | pages = 102–12 | date = February 2011 | pmid = 21357496 | url = http://www.jaoa.org/content/111/2/102.full.pdf+html | access-date = 27 May 2013 | archive-date = 13 January 2013 | archive-url = https://web.archive.org/web/20130113165349/http://www.jaoa.org/content/111/2/102.full.pdf+html | url-status = dead }}</ref>

====Muscles of mastication====
{{main|Muscles of mastication}}
The muscles of mastication are paired on each side and work together to produce the movements of the mandible. The main muscles involved are the masseter, temporalis and medial and lateral pterygoid muscles.

<gallery mode="packed-hover" heights="160">
File:Gray383.png|Left medial and lateral pterygoid muscles
File:Gray382.png|Left temporalis muscle
File:Gray378 (masseter highlight).png|Left masseter muscle (red highlight)
</gallery>

They can be thought of in terms of the directions they move the mandible, with most being involved in more than one type of movement due to the variation in the orientation of muscle fibers within some of these muscles.

* Protrusion – Lateral and medial pterygoid.<!-- <ref name="Standring 2006" />  -->
* Retraction – Posterior fibers of temporalis (and the digastric and geniohyoid muscles to a lesser extent).<!-- <ref name="Standring 2006" />  -->
* Elevation – Anterior and middle fibers of temporalis, the superficial and deep fibers of masseter and the medial pterygoid.<ref name="Standring 2006" />
* Lateral movements – Medial and lateral pterygoid<!-- <ref name="Standring 2006" />  --> (the ipsilateral temporalis and the pterygoid muscles of the contralateral side pull the mandible to the ipsilateral side).<ref name="Kerawala 2010">{{cite book|veditors=Kerawala C, Newlands C|title=Oral and maxillofacial surgery|year=2010|publisher=Oxford University Press|location=Oxford|isbn=9780199204830|pages=342–351}}</ref>

Each lateral pterygoid muscle is composed of 2 heads, the upper or superior head and the lower or inferior head.<!-- <ref name="Standring 2006" /> --> The lower head [[Origin (anatomy)|originates]] from the lateral surface of the [[lateral pterygoid plate]] and [[Insertion (anatomy)|inserts]] at a depression on the neck of mandibular condyle, just below the articular surface, termed the [[pterygoid fovea]].<!-- <ref name="Standring 2006" /> --> The upper head originates from the infratemporal surface and the infratemporal crest of the greater wing of the [[sphenoid bone]].<!-- <ref name="Standring 2006" /> --> The upper head also inserts at the fovea, but a part may be attached directly to the joint capsule and to the anterior and medial borders of the articular disc.<ref name="Standring 2006" /> The 2 parts of lateral pterygoid have different actions.<!-- <ref name="Scully 2008" /> --> The lower head contracts during mouth opening, and the upper head contracts during mouth closing.<!-- <ref name="Scully 2008" /> --> The function of the lower head is to steady the articular disc as it moves back with the condyle into the articular fossa. It is relaxed during mouth closure.<ref name="Scully 2008" />