Occlusion 1 - TMJ and Mandibular Movements Flashcards
What is TMJ ?
Joint between condyle of mandible and mandibular fossa of temporal bone.
What type of joint is TMJ ?
Synovial, condylar, hinge joint.
What is the attachment of anterior articular disc ?
Lateral pterygoid at articular eminence.
What is the attachment of posterior articular disc ?
Mandibular fossa of temporal bone.
What is another term for posterior articular disc ?
Retrodiscal tissue.
Explain why posterior articular disc is reason for TMJ pain.
Articular disc is largely avascular.
Retordiscal tissue is the area of disc which is vascularised and contains nerves - so common site of TMJ pain.
What ligaments attach condyle to articular disc ?
Medial and lateral collateral ligaments.
What are the two mandibular movements ?
Rotation.
Translation.
Define rotation.
Small amount of mouth opening (<20mm).
Condyle and disc remain in articular fossa with no protrusion.
i.e. ‘hinge movement’ - rotation of condylar heads around theoretical horizontal line through rotational centres of condyles.
Define terminal hinge axis.
Theoretical imaginary horizontal line through rotation centres of condyles.
How can terminal hinge axis be recorded ?
Using face bow - insert into ears - closes proximity to TMJ.
Define translation.
Anterior movement of condyle along incline of articular eminence to maximum mouth opening on contraction of lateral pterygoid.
What diagram shows border movements of mandible ?
Posselts envelope.
What does Posselts envelope describe ?
Extremes of mandibular border movements in sagittal plane.
What is ICP ?
Intercuspal position or centric occlusion or maximum interdigitation of teeth.
Comfortable bite.
In a patient with canine guidance, in edge to edge position, how should their occlusion look ?
Posterior spacing between mandibular and maxillary teeth.
In a patient with group function, in edge to edge position, how should their occlusion look ?
All teeth (anterior and posterior mandibular and maxillary teeth) in contact.
Define retruded axis position.
Most superior anterior condylar head position in fossa.
Where to measure terminal hinge axis.
Define retruded contact position.
First tooth contact when mandible in retruded axis position.
In 90% of population, where is RCP in relation to ICP ?
1mm posterior to ICP.
What diagram describe lateral translation of mandible ?
Posselts envelope in frontal plane.
Define Bennet angle.
Path of non-working condyle in horizontal plane during lateral excursion.
What anatomical feature prevents extreme lateral movement of working side in lateral translation ?
External wall of glenoid fossa.
