Packing and processing PMMA Flashcards
What is packing?
Involves the removal of wax and any temporary base plate - lost wax technique
Then created void filled with acrylic resin - this is called packing
What is processing?
After packing…
flasks placed into water based heat source or dry heat oven in order to cure resin
What do you do with the flasks with plaster and stone in them?
Placed in boiling out tank - water run onto flasks for 7-10 mins
How long should flask with cement and stone in it be placed in the boiling out tank?
7-10 mins
Temp of water bath for flask with cement and stone?
100 dc
What is the base plate made of?
shellac based base plate
What is occuring here?
Wax knife used to tease apart flask
Wet is this going?
Boiling out tank to remove left over wax
Using hand held water other residues
After the flask has returned from its second boiling out session - what material should you mix?
Acrylic resin
Poly (polymer powder)
Methyl methacrylate (liquid)
What consistency do you want for the poly methyl methacrylate to know it’s mixed?
Wet sand - cover
What consistency do you want for the poly methyl methacrylate after 5 mins and ready to use?
Doughy state
After boiling out wax, how do you secure loose teeth?
Super glue
What is being brushed on?
Separating medium - sodium alginate
Prevent absorption of monomer into the plaster
When it has dried, remove excess with air nosel
Why apply sodium alginate to plaster?
Prevent absorption of monomer into the plaster
What sheets have been placed over upper and lower model?
Polythene separating sheets
Why place polythene separating sheets?
How to place doughy POMA into flask?
Roll into a sashes shake and cover mould with other half of flask
What machine is used to press the flak?
Pneumatic press
How do you add pressure to the flaks in the pneumatic press?
Twist handle to secure flasks
Slowly apply pressure to the pump handle
How do you slowly apply pressure to flasks?
Pump pressure handle a few tie and leave for 45 seconds
Repeat process
After pneumatic press - what is happening here?
Wax knife used to remove most of the excess resin
Leaving only a rim of around 5 mm around denture
Do you related the press procedure after removing excess acrylic?
Yes. Ever to apply more sodium alginate and remove separating sheets
Do you fully tighten the flaks here?
No
Release pressure by quarter turn
Why do you not fully tighten flasks here?
Release pressure slightly by quarter turn
Accommodate for initial expansion in water bath
What is this called?
Spring clamp
What are the flasks in the sling co placed in?
Water bath - 72 Celsius 16 hours
Or dry heat processor - run overnight
Water bath temp for setting acrylic?
72 dc 16 hours
How long does the dry heat processor run?
Overnight
