FP - impression techniques

Question 1

name the 2 hydrophillic impression materials

Answer 1

alginate (irreversible)
agar Van R (reversible)

Question 2

name the 3 hydrophobic elastomeric impression materials

Answer 2

silicones
polysulphides (permlastic)
polyethers (impregum)

Question 3

why are hydrophobic impression materials not ideal?

Answer 3

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

Question 4

name the types of silicone impression materials

Answer 4

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

Question 5

what is alginate impression material used for?

Answer 5

removable pros - chromes

Question 6

when must alginate impressions be poured?

Answer 6

less than 24 hours after impression taken

Question 7

what type of tray does agar require?

Answer 7

tray with cooling mechanism

Question 8

what is the crucial requirement for sillicone impressions?

Answer 8

dry prep

Question 9

what are the advantages of agar impressions?

Answer 9

very accurate and stable (2 years)
can be disinfected

Question 10

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

Answer 10

leave for over an hour

Question 11

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

Answer 11

leave for 24 hours before pouring

Question 12

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

Answer 12

addition

Question 13

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

Answer 13

Affinis

Question 14

what are properties of polyethers (Impregum)?

Answer 14

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

Question 15

what are properties of polysulphides (permlastic)?

Answer 15

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

Question 16

what polyether impression material is used in DDH?

Answer 16

pentamix

Question 17

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

Answer 17

rigid tray - made from cold cure acrylic

Question 18

what is the issue with rim-lock trays?

Answer 18

cant cut them out of the mouth

Question 19

would you use a special tray with polyether?

Answer 19

no, it is too stiff

Question 20

what impression technique is used for cast post and core?

Answer 20

putty/ wash - 1 stage

Question 21

general rules for impression technique in fixed pros?

Answer 21

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

Question 22

explain the putty wash 1 stage technique?

Answer 22

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

Question 23

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

Answer 23

double helix mixer tip

Question 24

explain the mono phase impression technique

Answer 24

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

Question 25

what is the average biological width?

Answer 25

2.04mm

Question 26

what does the biological width consist of?

Answer 26

epithelial attachment supracrestal connective tissue attachment

Question 27

what happens if you violate the biological width?

Answer 27

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

Question 28

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

Answer 28

5mm

Question 29

how are soft tissues managed pre operatively?

Answer 29

sort perio pre-operatively surgically lengthen crown

Question 30

how do you manage soft tissues before impression?

Answer 30

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

Question 31

how can you remove the gingivae in soft tissue management?

Answer 31

electrocautery scalpel high-speed (troughing)

Question 32

what can retraction cord be soaked in for haemostasis?

Answer 32

ferrous sulphate/ aluminium chloride

Question 33

what patients can you not carry out electrosurgery on?

Answer 33

pts with pacemakers

Question 34

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

Answer 34

surgical crown lengthening

Question 35

what is the local regime for disinfecting impressions?

Answer 35

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

Question 36

when would you use pick-up impressions?

Answer 36

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