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4TH YR- CAD- pros tutorials > Primary impressions for conventional and complete dentures > Flashcards

Primary impressions for conventional and complete dentures Flashcards

1
Q

List the clinical and technical stages we carry out to make a denture

A
  1. Primary impressions
  2. Cast models and create special trays (Lab)
  3. Secondary impression
  4. Cast models and create record rims (Lab)
  5. Jaw registration
  6. Mount on articulator and set up teeth (LAB)
  7. Try in
  8. process to finish
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2
Q

What should a primary impression aim to record

A

The entire functional denture bearing area to ensure maximum support, retention and stability for the denture during use

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3
Q

List key features seen on a upper impression

A
  1. Hauler notch
  2. Vibrating line
  3. Fovea paatinae
  4. Palatal rugae
  5. incisive papilla
  6. Labial frenum
  7. Labial sulcus
  8. Buccal frenum
  9. Buccal sulcus
  10. Mucogingival line
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4
Q

List key features seen on a lower impression

A
  1. Retromolar pad
  2. Lingual sulcus
  3. Lingual frenum
  4. Pear shaped pad
  5. Buccal sulcus
  6. Buccal shelf
  7. Labial sulcus
  8. Buccal frenum
  9. Labial frenum
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5
Q

What makes a good impression

A
  1. Tissues recorded without distortion
  2. Completed with minimal discomfort to the patient
  3. must over the maximum denture bearing area
  4. Should be free of significant defects
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6
Q

What makes a bad impression

A
  1. Significant voids
  2. under extension
  3. Overextension
  4. impression material not adhering to tray
  5. Impression that does not cover full denture bearing area
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7
Q

What things can lead to a bad impression

A
  1. Incorrect tray selection eg using edentulous tray for no edentulous patient
  2. stock tray being under extended so alginate impression being too high
  3. Impression tray not being seated centrally leading to widening and narrowing of sulcus
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8
Q

What material scan we use for a primary impression

A
  1. Impression compound
  2. Alginate
  3. Silicone
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9
Q

What impression compound

A

A thermoplastic material

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10
Q

What do we mean by thermoplastic material

A

Softens with heat, hardens when cool

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11
Q

What are some advantages of impression compound

A

Can repeat the impression until the impression is correct

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12
Q

What 3 parts make up impression compound

A
  1. Resins
  2. Filler
  3. Plasticiser
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13
Q

Give examples of resins in impression compound

A
  1. Paraffin wax
  2. Beeswax
  3. Shellac
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14
Q

Give examples of fillers in impression compound

A
  1. Talc

2. Chalk

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15
Q

Give examples of Plasticers in impression compound

A

Stearic acid

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16
Q

Why is plaster added to impression compound

A

To make it more flowable in the mouth

17
Q

what can happen if impression material is left in the water bath for too long

A

The plasticiser will leach out meaning the impression won’t be as soft as ti was before

18
Q

How do we prepare to use impression compound

A
  1. Place cloth at Bottom of plastic bowl
  2. Soften it in a water bath (55-60 degrees)
  3. Takes couple of minutes to soften
  4. once completely soft place into impression tray
19
Q

What are the advantages of impression compound

A
  1. Non toxic
  2. Easy to use
  3. Can be re softened
  4. Muco displasive
  5. Corrects gross tray problems
20
Q

What are the disadvantages of impression compound

A
  1. Poor surface detail

2. Poor dimensional stability so needs to be cast up quickly

21
Q

How can we correct and improve the poor surface detail achieved from impression compound

A

Add an alginate wash

22
Q

What is alginate

A

An irreversible hydrocolloid

23
Q

Do we tend to use alginate on its own

A

no

24
Q

What do we usually do before taking a primary impression with alginate

A

Extend the stock tray using compound or silicone

25
Q

What are the advantages of alginate

A
  1. Easy to use
  2. Well tolerated
  3. Elastic
  4. Viscosity can be altered by adjusting water ratio
  5. Good surface detail
  6. Mucostatic
26
Q

What are the disadvantages of alginate

A
  1. Poor stability after setting
  2. Cannot bearded to
  3. Is at risk of drying out, shrinking and syneresis
  4. Swelling and imbibition if placed in too much water
  5. Poor tear resistance
  6. Requires adhesive to stick to tray
  7. Unsupported alginate is lilt to distort
27
Q

What is syneresis

A

When sign chains of the polyene contract squeezing all the water out of the material

28
Q

What is silicone putty

A

A polydimethyl siloxane and platinium catalyst

29
Q

What type of polymerisation does silicone putty undergo

A

Condensation polymerisation
or
addition polymerisation

30
Q

What are the advantages of silicone putty

A
  1. Easy to mix
  2. Easy to use
  3. Moderate surface detail
  4. Well tolerated
  5. Elastic
  6. Supports its own weight
  7. Mucocompressive
31
Q

What are the disadvantages of silicone putty

A
  1. Expensive
  2. Needs tray adhesive
  3. Long setting time
    4, hydrophobic so Better to have a dry mouth
32
Q

What do we write on the lab prescription when sending off out primary impression

A
  1. Draw tray outline 2 mm short of periphery on the impression before sending off
  2. Decide on the need for spacing or close fitting design.
  3. Ask for the upper handle on the special tray to be slightly labially proclined

4TH YR- CAD- pros tutorials (9 decks)

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