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IODC - IRS > Impression for Indirect Restorations > Flashcards

Impression for Indirect Restorations Flashcards

1
Q

What factors will make a good impression?

A

Tray choice inc. size
Appropriate technique
Good soft tissue management
Appropriate choice/use material

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2
Q

What different trays are available?

A
  1. Metal (e.g rim-lock)
    Reusable, can be perforated
    Adv: rigid- help support material to maintain pressure
    Disadv - need sterilising
  2. Plastic
    Disposable
    Disadv: not as rigid - more prone distortion
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3
Q

How can you assess size of tray?

A

Space space for seating and adequate room for imp

Place in mouth and hold handle - rotate lateral (if contact posterior suggest too small)

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4
Q

How can trays be more retentive?

A

Grooves, perforation

Use adhesive

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5
Q

Define accuracy?

A

Ability to replicate the hard and soft tissues

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6
Q

Define resolution/ precision?

A

Ability to reproduce surface detail

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7
Q

What is dimensional stability?

A

Maintenance of material in terms of size and shape over prolonged period of time

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8
Q

What are the classifications of impression materials?

A
  1. Hydrocolloids - reversible or irreversible (alginate)

2. Synthetic elastomers - polysulphides/polyetheres/ silicones

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9
Q

What are ideal characteristics for imp material?

A

High accuracy, good dimensional stability, elastic, good tear strength, easy use, good working and setting time, tolerant disinfection, cheap, acceptable taste

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10
Q

Properties/ use of alginate?

A

Poor reproduction surface detail
Poor dimensional stability
Not suitable definitive indirect impression
Used for opposing arch imps

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11
Q

Properties/ use of polysulphides?

A

Not used

Adv = long working time, flexible, good tear resistance, long shelf-life

Disadv = long working time, poor dimensional stability, stick, unpleasant smell, need special try

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12
Q

What is condensation silicone?

A

Cheaper than addition silicones
By product = alcohol

Adv: easy to use, good surface detail, good tear resistance
Disadv: dimensionally unstable, hydrophobic

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13
Q

What are addition silicones?

A

Most commonly used imp material for indirect restorations
Addition reaction between silane and vinyl groups when catalyst and base pastes are mixed

No-by product

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14
Q

Adv and disadv of addition silicones?

A

Adv: excellent dimensional stability, excellent surface detail reproduction, biocompatible, simple mixing, reasonable working time

Disadv: expensive, hydrophobic, setting time affect by temp, difficult to remove from cast, some latex glove inhibit setting

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15
Q

What are different formulation of addition silicones?

A

Putty
Heavy bodied
Medium bodies
Light bodied

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16
Q

What are different properties of formulations of addition silicones?

A

Light/ medium - more flowable and high detail reproduction
Putty - increased filler content (increase dimensional stability)
Heavy bodies - lack of contraction, dimensional stability

17
Q

Use of polyether as imp material?

A

Option for fixed prosthodontics
Rigid - favoured for things such as implants but makes difficult to remove from mouth (may remove periodontally compromised teeth)

18
Q

Adv and disadv of polyether?

A

Adv: good dimensional stability and surface reproduction, one viscosity - shear thinning allows flow, hydrophilic

Disadv: very stiff/ rigid, swell w/ water if kept damp environment, bitter taste

19
Q

Why do imps need to be disinfected?

A

Remove blood/saliva contaminant

Rinse to remove visible debris then follow procedure

20
Q

What are the 3 types of soft tissue management?

A

Mechanical - retraction cord

Chemical - retraction paste, homeostatic agent

21
Q

What is gingival retraction?

A

Downwards and outward movement of free gingival margin
Allows syringe imp material beyond prep margins
Doesn’t control inflammation

22
Q

What is retraction cord and what techniques can be used?

A

Cord = packed into gingival sulcus to retract gingiva

Single cord technique - most common removed prior to imp
Double cord - fine cord used initial (vertical) then pack largest above (vertical and lateral) - leave fine cord for imp

23
Q

What is haemostatic agent?

A

Aluminium chloride/ epinephrine to control bleeding

24
Q

What is retraction paste?

A

Viscous agent syringe into gingival sulcus to provide retraction and haemostats
More expensive

25
Q

When is soft tissue lasering used?

A

To widen or recontour gingival profile

Widen gingival sulcus/ remove overgrown tissue

26
Q

How to use addition silicone?

A
  1. Twin mix or one stage - at least two viscosities used and started in mouth together
  2. Two stage
27
Q

How to use twin mix/one stage imp with addition silicone?

A
  1. Tray selection - apply adhesive
  2. Soft tissue management if needed (retraction cord)
  3. Place putty/ heavy body into tray
  4. Remove retraction cord if needed
  5. Dry teeth
  6. Syringe light body around prep - start with gingival sulcus and end coronal part
  7. Add light body onto tray
  8. Seat imp
  9. Remove one direction - don’t jiggle
28
Q

How to use two stage imp for addition silicone?

A
  1. Tray selection- apply adhesive
  2. Pick material - spacer placed
  3. Take impression (essential creates special tray)
  4. Follow step for twin mix
29
Q

Should use twin mix or two stage imp?

A

Case dependent
Single stage - easier and quicker
Putty - high viscosity needs high pressure which can distort light body

30
Q

How to assess impression?

A 
Well defined margin
Good surface detail
No drags or voids
No tray exposure
All prep in appropriate material
Impression adhere to tray
31
Q

What to do if can’t see finish line?

A

Could be problem with finish line - may need refine/ smoothing
Problem impression - excessive bleeding/ gingocrevicular fluid/ enough gingival retraction

32
Q

What to do if air bubble/ void/ drag?

A

Drying tooth important
Keeping tip of syringe within material and start from finish line and end occlusally
Whole impression tray needs to be filled - supported all direction
Chose correct tray size

IODC - IRS (12 decks)

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