The temporomandibular joint, or TMJ, is the articulation between the condyle of the mandible and the squamous portion of the temporal bone.
The condyle is elliptically shaped with its long axis oriented mediolaterally,The articular surface of the temporal bone is composed of the concave articular fossa and the convex articular eminence
The MENISCUS is a fibrous, saddle shaped structure that separates the condyle and the temporal bone. The meniscus varies in thickness: the thinner, central intermediate zone separates thicker portions called the anterior band and the posterior band. Posteriorly, the meniscus is contiguous with the posterior attachment tissues called the bilaminar zone. The bilaminar zone is a vascular, innervated tissue that plays an important role in allowing the condyle to move foreward. The meniscus and its attachments divide the joint into superior and inferior spaces. The superior joint space is bounded above by the articular fossa and the articular eminence. The inferior joint space is bounded below by the condyle. Both joint spaces have small capacities, generally 1cc or less.
Normal TMJ Function
When the mouth opens, two distinct motions occur at the joint. The first motion is rotation around a horizontal axis through the condylar heads. The second motion is translation. The condyle and meniscus move together anteriorly beneath the articular eminence.
In the closed mouth position, the thick posterior band of the meniscus lies immediately above the condyle. As the condyle translates forward, the thinner intermediate zone of the meniscus becomes the articulating surface between the condyle and the articular eminence. When the mouth is fully open, the condyle may lie beneath the anterior band of the meniscus.
Imajing of TMJ
:Transcranial:the only radiograph in diagnostic position of TMJ
Transpharengeal:in semi opened position with no superimposition from skull
:Reverse town:in opened position shows high fracture of condyle.
transorbital:mediolateral planeshowing condyle + condylar neck
submentovertix: needed b/f CT & MRI for correcting position
CT: in case of cyst &tumors ,resorbtion ,etc
conventional tomography : allow for diagnostic position view.
Soft tissue by using:
Arthrography to see the disc indirectly
is not used extensively anymore since noninvasive MR imaging has replaced it.
MRI:to see the disc directly in coronal &sagittal views
Normal function of TMJ
Abnormalities of TMJ
abnormalities include develpmental,pain dysfunction syndrome,disc displacement,Trauma,&Tumors
TMJ Anatomy - Atlanta Dental Group PC
Anterior disc diplacement is most commonly occur
could be displaced with reduction(ADDR) i.e. disc displaced in close position
Anterior disc displacement without reduction(ADD) i.e.disc displaced in both open &close