Occlusion in relation to RPDs

Question 1

Why is occlusion important in RPDs?

Answer 1

Get it wrong and the patient will not tolerate the denture, no matter how well it fits the arch.

Question 2

Is making a partial denture the same process as complete dentures?

Answer 2

No!
The patient has natural teeth remaining which will influence the occlusion, position of teeth, occlusal plane etc
The number, condition, location position etc of remaining teeth has a significant impact on the denture construction process from planning/ design through to delivery of the denture

Question 3

ICP =

Answer 3

Intercuspal position

The point of maximum intercuspation between the teeth

Question 4

Centric relation =

Answer 4

Relationship of the mandible to the maxilla when the condyles are seated in the midmost uppermost position in the glenoid fossa.

Question 5

Centric relation - jaw or teeth relationship?

Answer 5

Centric Relation is a Jaw relationship, and is nothing to do with the teeth

• it is the optimum position for the neuromuscular system.
• it is a very useful position for the restorative dentist as it is reproducible and generally tolerated well by patients
• you will have used this already when constructing complete dentures

Question 6

Retruded contact position

Answer 6

Retruded Contact Position (RCP) is related to the teeth

The first tooth contact when the condyles are fully seated in the glenoid fossa

Question 7

Vertical dimension =

Answer 7

Vertical dimension of occlusion, or VDO, also known as occlusal vertical dimension (OVD) is a term used in dentistry to indicate the superior-inferior relationship of the maxilla and the mandible when the teeth are situated in maximum intercuspation.

Question 8

Defining your RPD case before starting

Answer 8

ICP

Vertical dimension

Question 9

Defining your RPD case before starting: ICP

Answer 9

• is it stable? Clear intercuspation between numerous teeth which pt consistently replicates
• if unstable/ unclear, often due to < n. tooth contacts or tooth wear, ICP not easy to replicate

Question 10

Defining your RPD case before starting: vertical dimension

Answer 10

Is the vertical dimension stable and acceptable?
The vertical dimension will not be stable if there are no remaining tooth contacts ie. If the remaining teeth do not oppose each other. The patient may be partially dentate in both arches or edentate in one arch.
The vertical dimension may not be acceptable in tooth wear cases where there has been significant loss of tooth height or where space is required to fit components of the denture such as the major connector or denture teeth

Question 11

Defining your RPD case: stable ICP and acceptable vertical dimension

Answer 11

Here you can proceed to make a mucosa borne denture, designing with the aid of study models.
For tooth borne dentures consideration must be given to the position of the occlusal rests. Therefore consider articulating the models prior to designing.

Question 12

Defining your RPD case: no stable/ unknown ICP, acceptable vertical dimension

Answer 12

Here you will establish a new ICP to coincide with Centric Relation.
Therefore you will need to establish the new occlusal scheme on registration rims and articulate the models prior to designing.

Question 13

Defining your RPD case: stable ICP but unacceptable vertical dimension

Answer 13

Here you will need to use registration rims to establish a new ICP at the correct vertical dimension to be coincident with Centric Relation

Question 14

Defining your RPD case: no stable/ unknown ICP, unacceptable vertical dimension

Answer 14

Here you will need to use registration rims to establish a new ICP at the correct vertical dimension to be coincident with Centric Relation

Question 15

Procedure for a simple acrylic RPD

Answer 15

Primary impressions 
-->Survey and design denture
Tooth preparation and secondary impressions 
Registration
Try-in
Fit
Review

Question 16

Primary impressions

Answer 16

Pretty essential no matter the case!

For very simple acrylic dentures replacing 1 or 2 teeth a good primary impression may be all that you require

Question 17

Denture design

Answer 17

After primary impressions you need to design the denture
To do this you must survey the casts
You also need to check how the teeth occlude so that no aspects of your denture interfere with the occlusion
-to do this you may simply be able to articulate the casts by hand if the occlusion is obvious
-if ICP is stable but you are concerned this may not be obvious on the casts you could take a silicone bite registration at the time of primary impressions
-however, you may need to get registration rims made at this stage and record the occlusion this way if it is not obvious when holding the casts together. If so, this adds a further visit to the denture construction process
To design a partial denture therefore, you ideally require surveyed and articulated study casts
Once you have designed the denture you can proceed to tooth preparation and secondary impressions

Question 18

Tooth preparation and secondary impressions

Answer 18

If rest seats are required make sure these are cut to appropriate dimensions
There need to be enough space for the rest without it affecting the occlusion
Don’t forget to leave enough space for the minor connector or clasp arm
Ensure that rest seat preparations are picked up well by the secondary impression

Question 19

Framework try-in (co/cr only)

Answer 19

First check the metal framework fits well on the cast and is fully seated
Then transfer to the mouth and ensure that the framework fully seats paying particular attention to the rest seats
Then check the occlusion – if conforming to current ICP make sure the occlusion is not altered
If required, adjust until the framework seats fully and doesn’t interfere with the occlusion

Question 20

Wax registration

Answer 20

This will be on a wax/shellac/acrylic base for acrylic dentures
This should be on the metal framework for a cobalt/chrome denture
Not only confirms occlusal relationship, but also tooth position, incisal plane etc

Question 21

Wax try in

Answer 21

Ensure the occlusion is identical to the wax registration
If there are discrepancies make any adjustments at this stage
This is the last chance to make changes!

Question 22

Fit

Answer 22

Again, check there have been no changes to the occlusion from the wax try-in stage
Make any adjustments as required
Check record?

Question 23

Metal backings

Answer 23

Very occasionally you may be providing a co/cr denture with metal backings
If so, you will need to do a tooth try-in at this stage to tell the technician where the denture teeth (and therefore the metal backings need to be)
If so, this adds a further visit to the denture construction process