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MODULE 6 > FP - impression techniques > Flashcards

FP - impression techniques Flashcards

1
Q

name the 2 hydrophillic impression materials

A

alginate (irreversible)
agar Van R (reversible)

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2
Q

name the 3 hydrophobic elastomeric impression materials

A

silicones
polysulphides (permlastic)
polyethers (impregum)

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3
Q

why are hydrophobic impression materials not ideal?

A

gingival crevicular fluid - but they are used for crown and bridge

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4
Q

name the types of silicone impression materials

A

addition cured - aquasil/ president/ affinis
condensation cured - Xantopren/ optosil

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5
Q

what is alginate impression material used for?

A

removable pros - chromes

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6
Q

when must alginate impressions be poured?

A

less than 24 hours after impression taken

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7
Q

what type of tray does agar require?

A

tray with cooling mechanism

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8
Q

what is the crucial requirement for sillicone impressions?

A

dry prep

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9
Q

what are the advantages of agar impressions?

A

very accurate and stable (2 years)
can be disinfected

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10
Q

what must you do when pouring an addition cured silicone impression?

A

leave for over an hour

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11
Q

what must be done to pour a condensation cured silicone impression?

A

leave for 24 hours before pouring

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12
Q

what type of impression is more accurate, addition or condensation cured silicone?

A

addition

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13
Q

what type of silicone (putty) do we have at DDH?

A

Affinis

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14
Q

what are properties of polyethers (Impregum)?

A

very accurate
rotten taste
stiff on removal - perio pt!!

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15
Q

what are properties of polysulphides (permlastic)?

A

long working time
great for undercuts (used in RP)
smelly

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16
Q

what polyether impression material is used in DDH?

A

pentamix

17
Q

what types of trays are a must for any fixed pros imp?

A

rigid tray - made from cold cure acrylic

18
Q

what is the issue with rim-lock trays?

A

cant cut them out of the mouth

19
Q

would you use a special tray with polyether?

A

no, it is too stiff

20
Q

what impression technique is used for cast post and core?

A

putty/ wash - 1 stage

21
Q

general rules for impression technique in fixed pros?

A

dry prep
block out undercuts
firm seating then NO pressure (support only)

22
Q

explain the putty wash 1 stage technique?

A

2 viscosities (putty and wash)
syringe wash around tooth, load impression tray with putty at the same time
seat putty in impression tray over wash before starts setting

23
Q

what is used for mixing of the wash in the one stage putty wash technique?

A

double helix mixer tip

24
Q

explain the mono phase impression technique

A

one viscosity - polyether/ med viscosity silicone
place some material in syringe
tray is loaded with same material
insert tray with impression material over syringed material

25
Q

what is the average biological width?

A

2.04mm

26
Q

what does the biological width consist of?

A

epithelial attachment
supracrestal connective tissue attachment

27
Q

what happens if you violate the biological width?

A

inflammation of gingival tissues
inflammation of periodontal tissues
bone loss
= recession

28
Q

what distance do we want between the gingival papilla and alveolar crest to base of proximal contact point?

A

5mm

29
Q

how are soft tissues managed pre operatively?

A

sort perio
pre-operatively surgically lengthen crown

30
Q

how do you manage soft tissues before impression?

A

temporarily displace gingival margin
retraction with braided cord with astringent, or injectable material (3M-ESPE/ Expasyl)

31
Q

how can you remove the gingivae in soft tissue management?

A

electrocautery
scalpel
high-speed (troughing)

32
Q

what can retraction cord be soaked in for haemostasis?

A

ferrous sulphate/ aluminium chloride

33
Q

what patients can you not carry out electrosurgery on?

A

pts with pacemakers

34
Q

what should be considered doing when there is inadequate occluso-gingival height?

A

surgical crown lengthening

35
Q

what is the local regime for disinfecting impressions?

A

10 x 1.7g Actichlor tabs per 1 litre water - 3 mins

36
Q

when would you use pick-up impressions?

A

if you fail to get a good impression of one or two preps

MODULE 6 (69 decks)

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