4th Session: Centric Relation (1-19, Sutton)

Question 1

What is centric relation (CR)?

Answer 1

A type of resting bite where the condyle is seated in the glenoid fossa (at the most superioanterior position!!) without tooth contact. The articular disk is properly interposed between the condyles and the articular fossae. At that position, rotation occurs around a fixed point or axis within the condyles. Note: the rotation is horizontal, vertical, and sagital!

Question 2

How is the articular disk attached to the capsular ligament?

Answer 2

Not only anteriorly and posteriorly but also medially and laterally. (This divides the joint into two distinct cavities).

Question 3

If a vector was drawn for each muscle of the TMJ, which direction would it point?

Answer 3

All muscle vectors are pointed supriorly and anteriorly.

This is because muscles are anterior to the TMJ and thus seat and brace the joint superiorly and anteriorly.

Question 4

When is the superior lateral pterygoid is especially active?

Answer 4

During the power stroke (closing against resistance) and when the teeth are held together.

(During this the inferior later pterygoid releases its contraction and is passive)

Question 5

Does centric relation position apply to those that are edentulous?

Answer 5

Yes. Whether dentate or edentulous, respect the centric relation position.

Question 6

What are the goals of dentistry?

Answer 6

1. Freedom from disease in all masticatory structures.
2. Maintainable healthy periodontium
3. Stable TJMs
4. Stable occlusion
5. Maintainable healthy teeth
6. Comfortable function
7. Optimum esthetics

Question 7

What is the starting point and primary requirement for occlusal therapy?

Answer 7

The joints must be able to function and accept loading forces with no discomfort.

Question 8

What are the requirements for anterior teeth for occlusal therapy?

Answer 8

The anterior teeth must be in proper relation with lips, tongue, occlusal plane.

Question 9

What are the requirements for posterior teeth for occlusal therapy?

Answer 9

The posterior teeth should be non-interfering with the comfort of the TMJ OR with anterior guidance.

Question 10

Where does movement of the mandible begin?

Answer 10

From centric relation position!

Question 11

What is forward translation of the mandible called?

Answer 11

Protrusion

Question 12

What is left lateral translation really?

Answer 12

Left working movement. The left joint stays seated and the mandible translates out of the right fossa.

Working = stays in the socket and twists.

Non-working = orbits

Question 13

At what separation can pure rotation opening occur?

Answer 13

Only until the teeth are 20-25 mm apart.

Question 14

Which direction does the mandible move when transitioning from CR to MI?

Answer 14

Protrusive in 90% of people.

Question 15

What are the 4 movements in the Envelope of Motions drawing?

Answer 15

1: posterior opening border - mimics the way the jaw opens (rotation, then unhinging).
2: anterior opening border
- a smooth curve
3: superior contact border
- show how the teeth slide forward and the open a bit to touch incisal edge to edge.
4: typical functional movement
- tear-shaped

Question 16

What shape do our horizontal border movements make?

Answer 16

They make a diamond shaped area.

Question 17

What does ICP stand for?

Answer 17

Intercuspal position

Question 18

What does EEC stand for?

Answer 18

End-to-end position

Question 19

What shapes are made for mandibular translation in the frontal plane?

Answer 19

Moving the mandible laterally creates a scoop motion in the front anterior teeth.

Question 20

What does MI stand for and what is its definition?

Answer 20

Maximal intercuspal position

The most complete interdigitation of the teeth independent of the condylar position.

Question 21

What is centric occlusion position?

Answer 21

When the teeth are in the position of 1st contact while the mandibular condyles are in their centric relationship positions.

Question 22

What happens when moving teeth from centric relation position to intercuspal position (ICP)?

Answer 22

A slide! Present in 90% of the population.

Average = 1-1.25mm

Question 23

Can CR = MI in the clinic?

Answer 23

Yes. Makes it much easier to treat

Question 24

What muscle contracts if the condyles are displaced when trying to reach maximum intercuspation?

Answer 24

The lateral pterygoid muscle.

Note: the condyles are pulled down as they are pulled forward.

Question 25

What are the centric relation clinical techniques?

Answer 25

1. chin point guidance*
2. bilateral manipulation*
3. leaf gauge*
4. lucia jig
5. swallowing
6. tongue back position

Question 26

What is the concept behind the leaf gauge?

Answer 26

Anterior deprogramming!

When only the anterior teeth occlude, the directional force provided by the elebator muscles seats the condyles in a superoanterior position within the fossae. The anterior stop from the leaves provides a fulcrum.

Question 27

What is the concept behind the anterior jig?

Answer 27

The Lucia jig also allows separation of the posterior teeth to interrupt or erase the proprioceptive mechanism of mandibular closure.

Question 28

What is done to the bite fork in the facebow?

Answer 28

Curved to adapt to the anterio-posterior curvature of the patient’s maxillary arch!

Question 29

How is the facebow oriented?

Answer 29

With the patient’s horizontal line at the eyes.

Question 30

What relationship must casts be mounted?

Answer 30

Centric relation!

Question 31

How are mounts verified?

Answer 31

Compare the initial point of contact on casts with the initial point of contact recorded on the patient.

ALSO: use multiple records and ensure the articulator condyles touch the articulator’s fossa!

Question 32

What are the small impressions called that are used to match up and mount the mandibular arch?

Answer 32

Records!

Question 33

What is the pin set to when mounting in CR?

Answer 33

To 0!