Occlusion in relation to RPDs Flashcards
Why is occlusion important in RPDs?
Get it wrong and the patient will not tolerate the denture, no matter how well it fits the arch.
Is making a partial denture the same process as complete dentures?
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
ICP =
Intercuspal position
The point of maximum intercuspation between the teeth
Centric relation =
Relationship of the mandible to the maxilla when the condyles are seated in the midmost uppermost position in the glenoid fossa.
Centric relation - jaw or teeth relationship?
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
Retruded contact position
Retruded Contact Position (RCP) is related to the teeth
The first tooth contact when the condyles are fully seated in the glenoid fossa
Vertical dimension =
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.
Defining your RPD case before starting
ICP
Vertical dimension
Defining your RPD case before starting: ICP
- 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
Defining your RPD case before starting: vertical dimension
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
Defining your RPD case: stable ICP and acceptable vertical dimension
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.
Defining your RPD case: no stable/ unknown ICP, acceptable vertical dimension
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.
Defining your RPD case: stable ICP but unacceptable vertical dimension
Here you will need to use registration rims to establish a new ICP at the correct vertical dimension to be coincident with Centric Relation
Defining your RPD case: no stable/ unknown ICP, unacceptable vertical dimension
Here you will need to use registration rims to establish a new ICP at the correct vertical dimension to be coincident with Centric Relation
Procedure for a simple acrylic RPD
Primary impressions -->Survey and design denture Tooth preparation and secondary impressions Registration Try-in Fit Review
Primary impressions
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
Denture design
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
Tooth preparation and secondary impressions
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
Framework try-in (co/cr only)
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
Wax registration
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
Wax try in
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!
Fit
Again, check there have been no changes to the occlusion from the wax try-in stage
Make any adjustments as required
Check record?
Metal backings
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
