OPTEC- Occlusion

Question 1

Compare rotation and translation

Answer 1

Rotation- the codyle and disc do not leave the articular fossa, it just rotates around the terminal hinge axis.

Translation- the condyle and disc move downwards and out of the articular fossa (caused by lateral pterygoid contraction)

Question 2

What is Posselts envelope?

Answer 2

The extremes of mandibular movements in the sagittal plane.

Question 3

Name this tooth position ?

Answer 3

This is intercuspal position (ICP)

This is the maximum interdigitiation of the teeth- known as the comfy bite.

Question 4

Name this tooth position

Answer 4

This is edge to edge-

The teeth slide forward from ICP. The icisal edges of the upper and lower insiors touch & the mandible is pushed forward.

Question 5

Name this tooth position

Answer 5

Protrusion

The condyle moves forwards and downwards on the articular eminence. Only the incisors (and sometimes the canines touch). There are no posterior tooth contacts.

Question 6

What is the maximum opening?

Answer 6

Mouth is wide open.

There are no tooth contacts.

There is full translation of the condyle over the articular eminence.

Question 7

Compare the retruded axis position and the retruded contact position?

Answer 7

Retruded Axis position- the most superior position of the condylar head in the fossa (no tooth contacts).

Retruded contact position- the first tooth contact when the mandible is in the retruded axis position. This is the position of the jaw when the tongue is touching the top of the mouth.

Question 8

What is the average difference between the RCP and the ICP.

Answer 8

The mandible normally slides forward about 1mm to achieve ICP

Question 9

Describe the two parts of the Bennet movement.

Answer 9

Working side- the side that the mandible is moving to

Non working side- the side that the mandible is moving away from (this moves forwards and inwards)

Question 10

What is the Bennet angle?

Answer 10

The path of the non-working condyle in the horizontal plane during lateral excursion.

Question 11

What is a mutally protected occlusion and why do we want it ?

Answer 11

This relieves the posterior teeth. Only the anterior teeth are subjected to lateral forces. (this allows the muscles of mastication to rest)

Question 12

When do you mark the tooth contacts and why?

Answer 12

Before preparing a tooth or removing a restoration (so you can replace the contatc points- preventing the new restoration from altering the occlusion)

AFTER

• Placing a crown (to check there are no heavy points and that the guidance is correct)
• Placing a restoration- to check that you haven’t altered the occlusion and that your margins are not directly under the contact point (causing weakness)

Question 13

What are the ICP contacts?

Answer 13

Lower buccal cusp contacts with fossa of the upper molar.

Upper palatal cusp contacts with lower molar fossa.

UP IB

Question 14

What does this articulation mark tell us?

Answer 14

There is canine guidance- the only contact is between the canines on the working side.

Question 15

What does this articulation mark tell us?

Answer 15

There is group function - Multiple teeth are in contact on the working side.

Question 16

What does this articulation mark tell us?

Answer 16

There is protrusion-

There are only incisor and canine contacts. The posterior teeth should not touch.

Question 17

What does this articulating mark mean?

Answer 17

There is a thick line on the 7- this indicates that we have a posterior contact.

It is on the working side (so it the similar cusps must be contacting)

Question 18

What does this articulating mark mean?

Answer 18

There is a line on the 6 which indicates a posterior contact.

Because the contact is on the non-workingside, it must be disimilar cusps that are contacting)

Question 19

What does this articulating mark mean?

Answer 19

There is a posterior contact during protrusion of the tooth.

Question 20

Why do we want to avoid posterior contacts?

Answer 20

Because posteiror teeth are not designed to absorb lateral forces (that are generated by occlusal interference)

They are designed to take the force down the long axis of the tooth.

Question 21

What are the two types of bruxism?

Answer 21

Eccentric- a side to side grinding of the teeth (more of a habit)

Centric- a more static position associated with clenching (on purpose)

Question 22

What are the clinical signs of bruxism?

Answer 22

• Tooth wear
• Fractured restorations
• Tooth migration
• Tooth mobility
• Muscle pain and fatigue
• Pain and stiffness in the TMJ and surrounding muscles.
• Headaches and earaches.

Question 23

How do we describe tooth wear?

Answer 23

Using the BEWE (Basic erosive wear Examination)

0-No erosive wear

1- Mild- inital loss of tooth surface

2- Moderate <50% tooth lost

3- Severe >50% of tooth surface loss

Question 24

What is fremitus and how do we test it?

Answer 24

This is palpable or visible tooth movement when subjected to occlusal forces.

We test this by placing our index finger on the tooth and getting the patient to tap their teeth together.

Question 25

Why do we use a facebow?

Answer 25

To record the relationship of the maxilla to the hinge axis rotation of the mandible .

Question 26

What is the relevance of the anterior reference point?

Answer 26

This is where the infra-orbital foramen is located.

43cm apical to the incisal edge of the anteiror teeth.

Question 27

Compare a conformative and re-organised approach.

Answer 27

Conformative approach- you are maintaining the patient’s existing occlusion. (the restoration is in harmony with the existing jaw relationship)

Re-organised approach- you are changing the patient’s occlusion to create a new, stable position.

Question 28

How does the re-organised approach work?

Answer 28

A stable occlusal contact is created with the guidance you have selected. This provides an occlusal stop.

We restore the canines to hold the contact in position.

We can use the re-organised occlusion to give us the space to finish the restoration of the occlusion.

Question 29

When would we use a re-organised approach with ICP?

Answer 29

When :

An increase in vertical height is needed to make space for the restorations.

The teeth are significantly out of position (overerupted/ tilted/ rotated)

Significant change in appearance is wanted.

Question 30

When do you use an RCP registration?

Answer 30

If the ICP is non-existent or no use (e.g. endentulous patients)

If you need space to place the restorations.

For intra-occlusal records (As RCP is independent of the teeth)

Question 31

How can we guide the patient to detect the RCP?

Answer 31

Chin point guidance

Bimanual manipulation.