M+O 10 - TMJs and articulators

Question 1

What needs to happen to protrude the jaw?

Answer 1

condyle needs to come forwards and down under the articular eminence

Question 2

What happens to the condyle on the working side?

Answer 2

rotates and slides vertically

Question 3

What happens to the condyle on the non-working side?

Answer 3

moves forwards and slightly medially

Question 4

Are the relationships between occlusal plane and joints arbitrary on an average value articulator?

Answer 4

no, set up to an average level

Question 5

What makes the hinge on an average value articulator more representative of a TMJ?

Answer 5

• 2 hinges, one ‘joint’ on each side
• can be locked or slide in a slot (represents the fact TMJ can slide)
• allows for protrusion and lateral movements

Question 6

What is an average value articulator used for?

Answer 6

• simple fixed prostheses for teeth not involved in guidance
• removable prostheses
• (used for virtually all removable prosthetics in the dental hospital)

Question 7

What is an arcon articulator?

Answer 7

condyle part of mandibular component

Question 8

What is a non-arcon articulator?

Answer 8

condyle part of maxillary component

Question 9

When talk about arcon and non-arcon articulators, what is the ‘condyle part’?

Answer 9

the ball

Question 10

What kind of articulator is a denar mark II?

Answer 10

arcon articulator (semi-adjustable)

Question 11

What kind of articulator is a dentatus articulator?

Answer 11

non-arcon articulator (semi-adjustable)

Question 12

What can a Denar Mark II articulator do?

Answer 12

• allows us to simulate hanging movements
• if locked can be extrusive movements
• has a ball and a slide to represent condyle and glenoid fossa
  
  • (ball attached to lower, slide on upper = arcon)

Question 13

To set up a semi-adjustable articulator, what do you do to get the hinge axis in the right place?

Answer 13

set measurements using face/ear bow
- sets upper jaw relative to the ears (ears easier to find on patient than condyles)

Question 14

How do you use a face/ear bow?

Answer 14

• Cover top of bite fork with wax and push against patients top teeth (NOT ‘bite’)
  
  • need a hard setting wax that isn’t going to distort
• Slide face bow onto frame until the back bits are in the ears
• This can then be used for the lab to relate the casts to the articulator correctly

Question 15

What are some of the drawbacks of semi-adjustable articulators?

Answer 15

• Costs more to buy
• takes longer to set up
• have to take time doing face bow etc
• more expensive for patient

So when do you choose to use different articulators?
- Need to look at patient’s occlusion, guidance etc

Question 16

What issues are there with using a facebow recording when setting up a semi-adjustable articulator?

Answer 16

• related maxillary cast to inter-condylar axis but uses ear as a reference
• orientation of cast in vertical dimension governed by a marker relating to the lateral incisor