Tutorial 3 - Preliminary jaw reg

Question 1

What is the reason for Preliminary jaw registration?
(Why is stage necessary?)

Answer 1

• To enable you to articulate your primary casts
  ( so you can ensure when designing the denture nothing interferes (eg rests))
• Can then study occlusion

Question 2

Why do primary casts need to be articulated?

Answer 2

• To enable you to accurately study the patient’s occlusion, on an articulator, whilst designing his/her denture

Question 3

What are we looking for during primary jaw reg?

Answer 3

• Over-erupted teeth – Is there room to fit in an opposing tooth / baseplate?
• Interdigitation – Is there room to place denture components, such as rests and clasp arms where you want them?
• (Eg do we need rest seats so that opposing teeth don’t get in the way/change occlusion, clasp arms need to be in correct position so that patient doesn’t bite onto metal and has tooth to tooth contact)

Question 4

steps for jaw reg?
(FROM IN PERSON SESSION)

Need to do it in a systematic way!!

Answer 4

• let patient bite without wax rims to see how patients jaw sits
• Can see what class occlusion
• Can see if there’s is enough space for the dentures to have teeth (sometimes they’re super erupted teeth so not a lot of space)
• Then trim wax until the rims sit in ICP
• Make notches
• Seals rim together with hydro bite
• This is then sent to lab with primary casts
• And they can survey to decide path of insertion and look at where undercuts are (this will help with designing your denture)

Question 5

What tool on surveyor is used to measure the undercut?

Answer 5

Undercut gages

Question 6

1
What are the different undercuts?

2
And what do they affect?

Answer 6

1
0.25, 0.5, 0.75

2
- Depth of undercut can affect the material you use, as it can impact the stiffness of materials you need

• 0.25 can use same denture based material as not as flexible as other materials
• 0.75 can use gold

Question 7

what is this?

Answer 7

articulator

• to see how teeth articulate

Question 8

1
How many clinical techniques are there for recording preliminary jaw registration?

2
what does the one you decide to use depend on?

Answer 8

1
- 2 different clinical techniques for recording the preliminary jaw registration

2
-The one used depends upon the number and position of remaining natural teeth

• you need to determine whether or not there is a position of maximum intercuspation

Question 9

What do you do if there IS a definite position of maximum intercuspation:

Answer 9

Familiarise yourself with occlusal contacts, before putting in bases

Ensure bases comfortable

Place the upper wax occlusal rim in the mouth and trim it until maximum intercuspation is re-established. (Natural tooth to tooth contact).

Remove from mouth and repeat with the lower wax rim (if there are 2 rims).

Put both wax rims in the mouth simultaneously and trim until maximum intercuspation re-established. (Natural tooth to tooth contact).

Cut grooves in the rims with a wax knife - (To hold registration material onto wax block)

Record position of maximum intercuspation using Zinc Oxide Eugenol paste or softened wax or a light- bodied silicone material.

Question 10

1
Before using Zinc Oxide Eugenol paste what do you need to check / do?

2
How is it mixed?

Answer 10

1
- Ensure your patient is not allergic to eugenol

• Smear vaseline on patient’s lips
• Explain about the strong taste
• Ensure patient’s clothes are well covered –
  It can be very messy if care is not taken!

2
Mixed :
Base and catalyst - equal amounts used to create uniform non streaky mix and apply to wax rims
If upper and lower wax rims- only need to apply to one and ask patient to close mouth until it has set and then remove from mouth

Question 11

What happens if there is NOT a definite position of maximum intercuspation

Answer 11

• a more complicated technique is required to record the jaw registration
• You will need to discuss your patient’s case in detail with your teacher.

Question 12

1
Where there is no definite position of maximum intercuspation, what do you do?

2
Why is it important to do this in this position?

Answer 12

1
- will need to record the relationship of the maxilla to the mandible in the retruded position

2
because it (retruded position) is a REPRODUCIBLE position

In exams always mention IT IS REPRODUCIBLE

Question 13

Retruded jaw relation DEFINITON

Answer 13

The relation of the mandible to the maxilla with the mandible in its most retruded position

Question 14

if you are lacking natural tooth contacts what may you need to record/determine?

Answer 14

• you may need to determine the vertical dimension at which you will record the jaw reg

Question 15

Vertical dimension definition

Answer 15

• a measurement of the face made between any two selected/ reference points
• one usu above and one below the mouth, usually in the mid-line
  (eg tip of nose + middle of chin)

Question 16

Rest vertical dimension (RVD)

Answer 16

Definition:
The vertical dimension with the mandible in the rest position

EXTRA
- When patient relaxed = rvd
(There will be small space between teeth when naturally relax mouth)

Question 17

Rest position

Answer 17

The position that the mandible passively assumes when the mandibular musculature is relaxed and the patient is upright

EXTRA
Rest position (relaxed position where we have a little bit of space between our teeth

Question 18

How to measure RVD of edentulous patient?

Answer 18

• require a Willis Bite Gauge or a pair of calipers
• patient needs to be sitting upright, with their head unsupported
• ask them to swallow
• When they’re done swallowing they’re mouth will open slightly automatically
• Do it multiple times
• Measure between 2 reference points (usu tip of nose and middle of chin
• Use willers gage to measure
• can have wax in mouth for RVD and OVD
• To make it easier can measure with and without wax
• Having obtained the RVD for your patient, work out the occlusal vertical dimension (OVD) that needs to be provided.

Question 19

1
OVD you are aiming for?

2
what do OVD + RVD stand for?

Answer 19

1
- 2-4mm less than RVD

2
- resting vertical distance
- Occlusal vertical distance (When patient bites )

Question 20

FREEWAY SPACE

1
what length are you aiming for?

2
how to calculate?

Answer 20

1
2-4 mm

If it’s smaller or larger it’s a problem so it’s important to get this right

Need to check and respect this freeway space when making denture

If free way space is not 2-4 mm then need to add or takeaway from wax

2
RVD - OVD

NOTE
- RVD should always be greater than the value for OVD in completed dentures

Question 21

What will happen if your free way space is too big eg 10mm? and what can this lead to?

Answer 21

• They will overbite
• The lips will point downwards
• Can lead to other issues eg angular cheilitis

Question 22

1
how should we should go about trimming our wax occlusal rims in the case where there are no natural tooth to tooth contacts?

2
why do we need to ensure this record is reproducible?

Answer 22

1
Firstly establish the patient’s RVD then trim the wax rims until you obtain the desired value for OVD (2-4mm less).

Then take your record using ZOE or wax as before, but in retruded position

2
Ensure this record is reproducible – WHY?

Because if it is not reproducible it is wrong (by definition) and will need re-doing

Don’t forget to disinfect the wax occlusal rims before sending them to the laboratory

Question 23

What instructions do you need to write on the laboratory prescription card?

Answer 23

• “Please use jaw registration record to articulate the primary casts”.
• (If special trays have not already been constructed these will also need to be requested)

Question 24

then you will survey the casts + design your denture

Place primary cast on surveyor
Work out path of insertion, guide planes and undercuts

Answer 24

Question 25

What do you think takes place at the next clinical visit?

Answer 25

• Confirmation of the design with your patient
• Any necessary tooth preparations
• Secondary impressions in special trays

Question 26

What was done before the preliminary jaw registration

Answer 26

• Patient was assessed
• Primary impressions were taken
• These were sent to laboratory and cast in dental stone to give primary casts
• Either asked technician to make wire reinforced wax bases and occlusal rims
• Or asked them to make special trays for secondary impressions (depends on type of denture being made - metal or not?)

Question 27

When wouldn’t you need to do the preliminary jaw reg stage?

Answer 27

For most acrylic dentures (no rests)

If there are no opposing teeth (i.e. opposing a complete denture)

If you can accurately articulate without a registration

• Only have secondary jaw reg for metal dentures

Question 28

NEXT FCs are from TUTORIAL, THEY MAY BE REPEATED OR NEW CONTENT

Question 29

How can you get a good articulation in a patient with a lot of posterior teeth missing (2 free end saddles) or edentulous?

(FROM TUTORIAL)

Answer 29

• Don’t have many teeth as guidance
• Can use Foxton’s…….
• Have to record it in RCP (retruded cuspal position)(this is where the patients joints are very comfortable- not strained - hence anatomically it should be reproducible position) (EXAM TIP - SAY RCP IS ANATOMICALLY THE MANDIBLE AND A REPRODUCIBLE POSITION)
• But IRL may actually be difficult to reproduce this position
• If problem with muscles or joints then it’s not easy to get this reproduced (as nothing really to guide them)
• Can manipulate the mandible with mandible manipulation
• HAVE WAX RIMS IN WHILE YOU DO THIS

Question 30

ONCE YOU’VE GOT THE DESIGNED THE DENTURE (random notes from tutorial)

Answer 30

• before patient comes in design and plan denture
• Can then show and explain denture design to them
• if patient hasn’t had metal denture before may not like the denture
• Better to do acrylic first to see if they’re okay with it as with metal you’ll need to do tooth preps
• They may want to go straight to metal denture
• Explain to them I’m going have to get rid of tooth structure and can’t guarantee they’ll be happy and comfortable to use dentures later on

Question 31

Overall process for preliminary jaw registration when there IS a definite position of maximum intercuspation:

Answer 31

Place the upper wax occlusal rim in the mouth and trim it until maximum intercuspation is re-established. (Natural tooth to tooth contact). Remove from mouth and repeat with the lower wax rim (if there are 2 rims).
Put both wax rims in the mouth simultaneously and trim until maximum intercuspation re-established. (Natural tooth to tooth contact).
Cut grooves in the rims with a wax knife
Record position of maximum intercuspation using Zinc Oxide Eugenol paste or softened wax

Question 32

Overall process for preliminary jaw registration when there is NOT a definite position of maximum intercuspation

Answer 32

Where there is no definite position of maximum intercuspation you will need to record the relationship of the maxilla to the mandible in the retruded position Because it is a reproducible position.
You may need to determine the vertical dimension at which you will record the jaw registration if you are lacking natural tooth to tooth contacts.
First of all you need to measure the patient’s rest vertical dimension (RVD)
To do this you will require a Willis Bite Gauge or a pair of calipers
Your patient needs to be sitting upright, with their head unsupported
Having obtained the RVD for your patient, work out the occlusal vertical dimension (OVD) that needs to be provided.
The occlusal vertical dimension you are aiming for will usually be 2 to 4mm less than the value you obtained for rest vertical dimension
i.e. RVD – OVD = 2 to 4mm
Note – the value for RVD should always be greater than the value for OVD in completed dentures

TRIMMING WAX OCCLUSAL RIMS :
Firstly establish the patient’s RVD then trim the wax rims until you obtain the desired value for OVD (2-4mm less).
Then take your record using ZOE or wax as before, but in retruded position
Ensure this record is reproducible Because if it is not reproducible it is wrong (by definition) and will need re-doing
Don’t forget to disinfect the wax occlusal rims before sending them to the laboratory