Primary Impressions and Primary Jaw Registration Flashcards
Why do you need primary casts?
saddles (what do the saddles look like and what are you going to put to replace?)
look at the occlusion (hand articulation to test or use an articulator)
undercuts - survey (see if there are undercuts for clasps to engage in)
lab (make primary models and to construct special trays)
What are the blue and clear trays used for?
deeper trays for patients with teeth (dentate)
What are the green trays used for?
for edentulous teeth
How should you hold the tray?
- Hold the FLAT side of the handle
- Hold the tray in front of you as you would
seat it in a patient’s mouth with the fitting
surface facing the teeth - Then decide which way round gives most
space for the lip/soft tissues
How can you modify the length and depth of the tray? (width is critical)
- Add ribbon wax (red soft wax) /greenstick (impression compound material)
- Remove overextensions with acrylic bur on straight handpiece
What impression material is normally used and what material should not be used on teeth?
alginate is used
impression compound should not be used on teeth only edentulous
Where can impression compound be used and why?
- Can use impression compound to capture the free-end saddle areas before taking impression in alginate
- Stabilizes the tray – reduces rocking
After compound is used, what should be applied?
Record free end saddle areas using compound.
Then apply alginate adhesive to tray and compound
Apply alginate to wash over compound to fill the tray
Why should alginate flow over the tray?
to capture sulcus area and avoid denture being overextended/underextended
How should the tray be inserted?
rotate the tray at 90 degrees to avoid patient gagging
What should be inspected in the impression?
it record edenulous areas
records sulcus of the denture border area
records teeth and has good detail of occlusal surfaces – occlusion
enables lab to make a good special tray
How should you decontaminate your impressions?
- Rinse
- Place in Perform for 10 minutes
- Indicate that impressions have been decontaminated on lab card
- Bag with wet cotton wool or paper towel and take to lab as soon as possible
Why is a wet cotton wool added?
minimise the resorption of the cast
When would you need a primary jaw registration?
if you casts can’t be hand articulated
What are index teeth?
The teeth that contact each time are called “index teeth”
What is hand articulation and does it require a primary registration?
- Can hold the casts together and they meet together the same way each time
- Reflective of what’s in patient’s mouth
- There are enough index teeth present
- You don’t need to record the occlusion and you don’t need a primary record block
- Lab will mount casts on an articulator
What is a wax wafer used for?
- You may wish to place a piece of warm wax into the patient’s mouth and have them bite together to confirm the occlusion to the lab
- This is referred to as a wax wafer and is an inter-occlusal record
- Where teeth contact, the wax should be pierced
- It is not always needed
If your casts can’t be Hand Articulated, what do you need?
- You need primary record blocks (rocking teeth - unstable)
- Upper shellac baseplate
- Lower wire strengthener
- Casts then mounted on articulator after registration is provided to lab
What is the most important thing when recording primary registration?
teeth still touching the same way they were with old dentures/ normal dentition
What might the index teeth not touching cause?
anterior over-bite
Increased occlusal vertical dimension
Inadequate freeway space
How is the primary regisration recorded?
- Bring primary record blocks to required occlusal level
- Add bite registration paste and ask the patient to occlude
- Check index teeth are still in contact
What could be the issues affecting index teeth in primary blocks?
Not enough wax removed from block?
Too much bite reg paste used?
Bite reg paste set before
patient occludes?
What step is added in casts that can’t be hand articulated?
primary jaw registration
What should you do before taking master impressions?
Design the denture
* Identify any teeth that may require modification eg rest seats/guide planes
* If planning a CoCr denture ask the lab to survey your primary casts and, following your primary jaw registration (if needed), mount on articulator and return to you along with special trays
* You can now design your denture prior to taking the master impression
In casts that can be hand articulated, what step is added for chrome dentures?
framework trial
What are record blocks made for?
where insufficient natural teeth are present to define the occlusion, blocks aid the articulation of models
