Occlusion 1 - TMJ and Mandibular Movements

Question 1

What is TMJ ?

Answer 1

Joint between condyle of mandible and mandibular fossa of temporal bone.

Question 2

What type of joint is TMJ ?

Answer 2

Synovial, condylar, hinge joint.

Question 3

What is the attachment of anterior articular disc ?

Answer 3

Lateral pterygoid at articular eminence.

Question 4

What is the attachment of posterior articular disc ?

Answer 4

Mandibular fossa of temporal bone.

Question 5

What is another term for posterior articular disc ?

Answer 5

Retrodiscal tissue.

Question 6

Explain why posterior articular disc is reason for TMJ pain.

Answer 6

Articular disc is largely avascular.
Retordiscal tissue is the area of disc which is vascularised and contains nerves - so common site of TMJ pain.

Question 7

What ligaments attach condyle to articular disc ?

Answer 7

Medial and lateral collateral ligaments.

Question 8

What are the two mandibular movements ?

Answer 8

Rotation.
Translation.

Question 9

Define rotation.

Answer 9

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.

Question 10

Define terminal hinge axis.

Answer 10

Theoretical imaginary horizontal line through rotation centres of condyles.

Question 11

How can terminal hinge axis be recorded ?

Answer 11

Using face bow - insert into ears - closes proximity to TMJ.

Question 12

Define translation.

Answer 12

Anterior movement of condyle along incline of articular eminence to maximum mouth opening on contraction of lateral pterygoid.

Question 13

What diagram shows border movements of mandible ?

Answer 13

Posselts envelope.

Question 14

What does Posselts envelope describe ?

Answer 14

Extremes of mandibular border movements in sagittal plane.

Question 15

What is ICP ?

Answer 15

Intercuspal position or centric occlusion or maximum interdigitation of teeth.
Comfortable bite.

Question 16

In a patient with canine guidance, in edge to edge position, how should their occlusion look ?

Answer 16

Posterior spacing between mandibular and maxillary teeth.

Question 17

In a patient with group function, in edge to edge position, how should their occlusion look ?

Answer 17

All teeth (anterior and posterior mandibular and maxillary teeth) in contact.

Question 18

Define retruded axis position.

Answer 18

Most superior anterior condylar head position in fossa.
Where to measure terminal hinge axis.

Question 19

Define retruded contact position.

Answer 19

First tooth contact when mandible in retruded axis position.

Question 20

In 90% of population, where is RCP in relation to ICP ?

Answer 20

1mm posterior to ICP.

Question 21

What diagram describe lateral translation of mandible ?

Answer 21

Posselts envelope in frontal plane.

Question 22

Define Bennet angle.

Answer 22

Path of non-working condyle in horizontal plane during lateral excursion.

Question 23

What anatomical feature prevents extreme lateral movement of working side in lateral translation ?

Answer 23

External wall of glenoid fossa.