Dentistry: Subluxation and Dislocation

Study Notes

The TMJ (Temporomandibular Joint) is a synovial joint between the head of the mandible and the mandibular fossa on the undersurface of the temporal bone.
The joint capsule is made of dense, irregular collagenous connective tissue and is richly endowed with sensory endings from the mandibular division of the trigeminal nerve.
The lateral temporomandibular ligament limits the movement of the mandible in a posterior direction and protects the external auditory meatus.
The sphenomandibular ligament and stylomandibular ligament also support the joint.
The articular disc is composed of dense fibrous connective tissue devoid of blood vessels or nerve fibers.
Synovial fluid is a clear, straw-colored, viscous fluid that lubricates the joint and provides nutrition to the surrounding tissues.

The TMJ receives its blood supply from branches of the superficial temporal arteries, deep auricular arteries, anterior tympanic arteries, and ascending pharyngeal arteries.
The nerve supply comes from the auriculotemporal nerve, masseteric nerve, and posterior deep temporal nerve, which are branches of the mandibular portion of the trigeminal nerve.

Agenesis of the condyle: unilateral or bilateral, resulting in anterior open bite and inability to close repeatedly to a fixed retruded position.
Hypoplasia of the condyle: limitation in mandibular opening and pain.
Hyperplasia of the condyle: limitation in mandibular opening and pain.

Rare, resulting from bacterial invasion or spreading infection to the TMJ.
Signs and symptoms include cardinal signs of inflammation, clicking of the joint, and deviation on opening.

Injury to the TMJ, including fracture of the condyle, which can result in pain, asymmetry of the face, swelling, limitation in movement, and deviation to the affected side during opening.
Subluxation: anterior position of the head of the condyle to the articular eminence, which can be unilateral or bilateral, and can be treated with physiological activity.
Dislocation: anterior position of the head of the condyle to the articular eminence, which can be unilateral or bilateral, and cannot be treated with physiological activity.
Clinical features of dislocation include pain, false Class III malocclusion, pretragus notch, drooling of saliva, improper speech, and hard locking.

A complication of trauma or infection involving the TMJ, which can be fibrous or bony, unilateral or bilateral, and is diagnosed by radiograph and treated by surgery.

A malrelationship of the meniscus to the condylar head and articular eminence.
Anterior displacement with reduction: sudden inability to bring the upper and lower teeth together in maximal occlusion, pain in the affected joint, displacement anteriorly of the mandible on the affected side, restricted lateral movement to the affected side, and no restriction of mouth opening.

An inflammatory, autoimmune disease primarily affecting periarticular tissue and secondarily bone.
The percentage of RA patients with TMJ involvement ranges from 40% to 80%.
Radiographic changes in the TMJ associated with RA may include a narrow joint space, destructive lesions of the condyle, and limited condylar movement.
Clinical findings include pain on joint palpation, limited mouth opening, and crepitus.

Characterized by arthritis, and include ankylosing spondylitis, psoriatic arthritis, and reactive arthritis.
Clinical manifestations include joint pain with function, limited mouth opening, and erosion of the superior surface of the condyle on radiography.

Systemic lupus, systemic sclerosis, undifferentiated connective tissue disease, and mixed connective tissue disease can affect the TMJ.

Gout: a disease that includes hyperuricemia, recurrent arthritides, renal disease, and urolithiasis, primarily affecting men.
Myositis: inflammation of the masticatory muscles, which can be caused by trauma, infection, or disease.