Provision Restorations Flashcards
Discuss why provisional restorations are important after preparation (5)
- Protect tooth from damage and sensitivity
- Aesthetics
- Function
- Prevent migration
- Evaluates the prep- parallel? reduced enough?
Why are provisionals important as a treatment planning tool? (3)
- useful for aesthetic cases- trial run
- Template for contour, contacts occlusion, aesthetics
- Plan/assess change in VDO
Technical requirements for provisionals (7)
Good margins
Good retention/resistance during function
Dimensionally stable
Aesthetically acceptable
Polishable (avoids plaque)
Easy to remove
Good handling, short set time
Pros (4) and Cons (4) of PMMA
Pros:
- Aesthetic, colour stability
- Good margins
- Polishable
- Good transverse strength
Cons:
- High shrinkage during setting
- Exothermic rxn, irritates pulp
- Low abrasion resistance (avoid in brux)
- Odour
Why can PMMA irritate the pulp and how to avoid?
high exothermic rxn during setting
- make temp on model extraorally
Pros (6) and Cons (3) of PEMA
Originally made to replace PMMA but lacks some advantages
Pros:
- Polishable, stain resistant
- good handling
- Better suited when temp needs to last long
- Lower exothermic rxn
- Lower shrinkage
- Less odour than PMMA
Cons:
- Low hardness, fracture resistance, tensile strength less than PMMA
- Less durable in high-stres areas, longer spans
- Poor colour stability
What form does PMMA , PEMA and resin temp materials come in
PMMA & PEMA - powder and liquid
Resin- preloaded syringe with automix tip
Pros (5) and cons (5) of bisacryl resin as a provisional material
Bisacryl resins comprised of resin mixed with filler
Pros:
- Low exotherm rxn
- low shrinkage
- Good marginal fit
- Good transverse strength
- Good abrasion resistance
Cons:
- Brittle
- O2 inhibited later (less stain resistant)
- Difficult to repair
- Limited shades
- $ > methacrylates
Pros (6) and cons (5) of Bis-GMA composite resin as a provisional material
Chemistry is similar to restorative composites
Pros:
- Less brittle than bis-acryls
- Repairable with flow
- Good margins
- Good frac resistance
- Highly polishable
- Low shrinkage
- Low exotherm rxn
- Many shades (aesthetic)
Cons:
- $
- More brittle than methacrylate
- poor stain resistance
- Not good for splinting
- Poor surface hardness
what is the matrix / copy technique (3)
matrix made using alginate/ silicone putty from models or wax up or direct
load with temp material
temps are trimmed, polished, cemented
what is the shell aka direct/indirect technique
Used in cases with multiple teeth with aesthetic demand
- basically replacing your shitty temps with better, lab made temps. OR replacing the preexisiting old crowns
- lab tech builds shell on study cast (they did the crown prep on the model)
- sends shell to you with seating jig (used to ensure shell is positioned the same as it was on model)
- prep tooth / cut existing crown
- adjust if needed
- reline with acrylic, lifting up and down to avoid locking onto teeth
- trim polish cement
what is the indirect technique
Provisionals are made by lab on model of PREPPED TEETH
- Useful for multiple teeth
- No need for intraoral relining
- Exotherm/shrinkage challenges eliminated
- Lasts for long time
What is a polycarbonate preformed crown?
Used as a matrix around prepared tooth
- High impact strength
- Abrasion resistance
- Good hardness
How to use polycarbonate preformed crown? (5)
Select size
check fit and occlusion
Trim margins, proximal walls, height
Fill with acrylic and seat
Cement in place
Pros (1) and cons (4) of metal provisionals
pros:
- quick, easy to adapt
cons:
- rapid wear
- limited to posterior (unaesthetic)
- can lead to extrusion
- unpleasant taste
Disadvantage of splinting adjacent temps
Hygiene
- Must clear gingival embrasures
- Impinged papilla can become inflamed quickly, perio defects
HOWEVER
if you thin it out too much, will become weak, small contact area and thus fracture prone.
Poyan said doesn’t matter. Still need to clear.
Spot-etch provisional veneer technique (6)
- Diagnostic wax up
- Alginate index of wax up, cutting away unnecessary parts so that temps arent thick
- Remove old veneers
- Spot etch, NO BOND
- Index loaded with protemp (comp), seat
- Remove excess, polish, cement
