CAD Copy dentures and relines Flashcards
what is a soft lining?
Soft cushioned lining inside the denture to stop pressure points and make eating more comfortable.
what are clinical indications of a soft lining?
-Persistent pain under denture
-Reduction of pain during function
-Previous positive experience of resilient (soft) linings
what two main material types are used for soft linings?
silicone and acrylic
what are downsides of using silicone soft lining?
-Silicone is inert and requires an adhesive to glue it to denture (can’t chemically bond to rest of denture). Debonding can happen as adhesive can fail.
-Prone to colonization with Candida (as it’s very porous)
What are downsides of using acrylic soft lining?
don’t feel as soft to the pt as silicone (silicone is ‘elastic’)
they are rigid so needs plasticiser to be added to give it a softening property. Plasticiers leach out with time leaving the material hard.
denture is more prone to fracture with soft linings- true or false?
true, as it is taking away from the space that the PMMA denture material would have been there. Rubber adds no strength to the denture, leaving the PMMA thinner and weaker.
what is minimum thickness of soft liner?
2mm
what is a denture reline?
If a denture becomes ill fitting due to the change in the shape of the tissues beneath over time, they can be relined to make them fit again.
what are problems with chair-side reline?
Problems – largely with upper dentures:
-Increase thickness of palate as has lining on top of it
-Can increase OVD- especially when relining upper denture (esp if pt has limited freeway space)
-Exothermic polymerisation (we use poly-methyl methacrylate, not as exothermic as PMMA but still a bit warm and can be uncomfortable)
-Monomers can be irritant / allergenic (pre-polymerised beads and liquid monomer and mix together, when at stringy stage we put on inside of denture).
-Destroys post-dam – retention may be reduced
-Reline materials chairside not as fully cured as lab materials
what are advantages of a lab rebase?
-No increase in OVD
-No thickening of palate
-Can include a new post dam
what are adv and disadv of doing a reline chairside?
Adv:
-Immediate result
-Fewer stages for errors to creep in
Disadv:
-Inferior physical and mechanical properties. Material not as strong as PMMA
-Free monomer present
-For partial dentures, reline material may lock into undercuts or in between standing teeth, making the denture very difficult to remove
what are adv and disadv of doing a reline in the lab?
Adv:
-Good physical and mechanical properties (PMMA used and cured under heat and pressure)
-Rebasing possible (for upper denture palate remains thin and we get a post dam)
Disadv:
-Pt w/o denture for some time
-Errors may creep in due to impression taking, model pouring, flasking, etc. (more stages = more chance for errors)
-If heat is used to polymerise the lining, the existing base material may warp
what is a tissue conditioner?
Quick procedure to offer instant improvement in fit and relief of pain. Very soft cushiony material like Visco-gel- lasts about a week. Can make denture temporarily much more comfortable, eg. if had ulcers/ stitches.
what are the two parts to Visco-gel tissue conditioner?
1-Powder (acrylic beads)
2-Liquid (solvent-dissolves beads. It is ethyl alcohol and plasticizer)
what are the uses of temporary soft lining materials/ tissue conditioners?
-To offer temporary relief from pain
-To help diagnose cause of pain
-To see if permanent soft lining would be of benefit
-Temporary improvement in fit of denture while new ones are being made
