Biomechanics of the TMJ Flashcards
Skeletal components TMJ
Maxilla
Mandible
Temporal bone
Disc
Dense fibrous C.T = slightly innervated
Articular surface of condyle = intermediate zone of the disc
Maintains morphology unless destructive forces/structural changes = can be irreversibly altered, biomechanical changes
Non ossified bone = both joint systems
True articular surface = both joint systems
What are joint cavities filled with
Synovial fluid
2 purposes of synovial fluid
- provide metabolic requirements to these tissues
- lubricant between the articular surface during function
Retrodiscal tissue
Loose c.t attaches to post part of disc
Highly vascularized and innervated
Innervation of TMJ
Trigeminal nerve - auriculotemporal nerve
Biomechanics of the TMJ
Complex joint system
2 TMJs connected to same bone - influence each other
TMJ - inferior synovial cavity (condyle and articular disc)
Disc + attachment to condyle = condyle disc complex
ROTATION
TMJ- superior joint cavity
Condyle disc complex functioning against the surface of the mandibular fossa
TRANSLATION
Do the articular surfaces of the joint have structural attachment / union ?
No but the contact must be maintained for joint stability
Stability of the joint
Maintained by constant activity of the muscles
Superior Retrodiscal lamina
Only structure capable of retracting the disc posteriorly on the condyle
Where does the superior lateral pterygoid attach
Anterior border of the disc
Active= pulls anterior and medially
Lateral pterygoid
Attached neck of condyle
Dual attachment! - allows the muscle to not pull the disc forward
What happens when the inferior lateral pterygoid is protracting the condyle forward?
Superior lateral pterygoid is inactive
Activates during mandibular closure
Mechanism by which the disc is maintained with the translating condyle is dependent on what
Morphology of the disc and the interarticular pressure
3 important principles of biomechanics of TMJ
-ligaments do not actively participate in normal function of the TMJ
- ligaments do NOT stretch, they elongate
- articular surfaces of the TMJ must maintain constant contact (produce by muscles of mastication (elevator))
Rotation
Inferior cavity of joint
B/w superior surface of condyle + inferior surface of articualr disc
3 planes = horizontal, sagittal, frontal
20-25 mm
Translation
Mandible moves forward
Superior cavity b/w superior surface of articular disc and inferior surface of articular fossa
40-60 mm
Envelope of motion
Maximum range of movement of the mandible
Controlled by neuromuscular system = avoid injury
Temporomandibular disorder
Several clinical problems that involve the masticatory musculature, TMJ and associated structures or both
Major cause of non dental pain
Most common symptoms of TMD
Pain
Limited asymmetric mand movement
TMJ sounds
Headaches, earaches, jaw pain, facial pain
TMD coexist with cranial mandibular + Orofacial pain
Epidemiology of tmd
40-75% 1 sign of joint dysfunction
~ 33% 1 symp
50% joint sounds
5% mouth opening limitation
Children less than adults
Women more than men
Women more likely seek tx
Only 3.6-7& need tx
Etiology of TMD
Predisposing factors - increase risk of TMD
Initiating factors - cause onset of TMD
Perpetuating factors- interfere with healing/enhance progression of TMD
Important: long term successful management
