Finishing/Flasking Flashcards
What happens in ‘flasking’
The waxed denture is sealed onto the duplicate cast and embedded in dental plaster into the deeper half of the denture flasks
Why is the palate left exposed in ‘flashing’
o This is where the light cure base gets placed so we need to make sure that there is space to remove that
o It is also because this is where we place the acrylic manually
On setting in the ‘flashing’ stage what is the plaster mould coated in
a separating medium (sodium silicate)
In the ‘flasking’ stage what is the mould completed with
with a 50/50 plaster/stone mix
What is done following the setting of the completed mould in ‘flashing’
The dental flask is immersed in hot water for 10 minutes to soften the wax inside.
When the flask is separated after ‘flashing’ what is the wax evacuated
with boiling water
What happens in the hooded method of flashing
the artificial teeth and clasps are held in the investing plaster following flasking.
What are the plaster surfaces and cast coated with in ‘packing’
a ‘mould seal’ to prevent plaster adhering or penetrating the denture.
When should the mixed PMMA be packed
when it has reached the dough stage
When packing the mould where should special attention be paid to
packing the mould around the teeth.
Why is the mould closed under pressure
To expel excess material which on re-opening is removed
After the excess PMMA is removed what is done
The two halves are closed and placed into a spring compress and processed
What is the powder in PMMA
the polymer
What is the liquid in the PMMA
the monomer
What is the ratio for PMMA
10mls to 24g
What happens if too much powder is used
can result in granular porosity
What should the PMMA be processed
under pressure in a hydraulic flask
Why should the PMMA be processed under pressure
otherwise the acrylic will expand and pull the acrylic apart resulting in contraction porosity
What else can result in contraction porosity
Having too little acrylic can also result in contraction porosity as well
Why should the heat be controlled when mixing PMMA
– it should not be too hot as this will cause it to boil too quickly and this will cause holes in the acrylic which will result in gaseous porosity
Why should the PMMA then be bench cooled
to relieve internal stress
How is the denture removed following processing
The plaster is removed from the mould and the plaster mould removed from the denture and cast
What are the advantages of cold cure
o very easy to do
o quick
What are the disadvantages of cold cure
o it is not processed properly so it is not polymerized properly meaning that the acrylic is softer than it would be in heat cure
o also means acrylic teeth aren’t fully processed and so if there is any heavy occlusal contacts these teeth will wear down quicker than in the heat cure process
o heat cure acrylic looks more natural than cold cure
How is the occlusion checked
This is done using the split cast system
Describe the process of checking the occlusion
The duplicate model (with denture) is secured to the original mounting with plaster bandage
The occlusion is checked and refined as required against the opposing dentition
What indicates the occlusal vertical dimension on checking the occlusion
The incisal post at rest on the incisal table indicates the occlusal vertical dimension
How is the duplicate model removed from the denture following occlusal refinement
by sawing the model from the denture
What happens following occlusal refinement and removal
The denture is finished and polished
What can be done following polishing of the denture
the denture can be fitted to the definitive cast
What do the denture on the definitive cast show regarding the clasps
The denture on the definitive cast shows the space between the clasp arm and the cast
What do we want to see with the clasp
Want a close adaptation of the finished clasp on the cast and want to ensure arm of the clasp is not anywhere near tissue or undercut and only the terminal end will be on the selected undercut
