T2b - Taking primary impressions

Question 1

(21/09/23 - ICC - primary impressions phantom head course)

Question 2

PART 1 - PRIMARY IMPRESSIONS

stages of primary impressions

Answer 2

1 - tray selection
2 - placing adhesive on tray
3 - mix putty
4 - placing putty in tray
5 - take putty impressions
6 - cut out putty placed in unwanted areas
7 - place alginate adhesive
8 - mix alginate
9 - place in upper tray
10 - rinse and disinfect impressions
11 - repeat on upper and lower arch

Question 3

1
how do you select a tray for primary impressions?

2
what anatomical landmarks should be covered by the tray?

3
are these trays disposable?

Answer 3

1
- do intraoral exam and choose appropriately sized stock tray - S, M, L

• ensure all teeth + anatomical landmarks are covered

2
- dentition present
- saddles (edentulous spaces)
- buccal + labial sulci
- maxillary tuberosities (if FES)
- maxillary hard palate
- mandibular buccal shelves, retromolar pad, retromylohyoid fossa (if FES)

3
- yes, use a disposable plastic tray

Question 4

what do you need to place on tray before putting impression materials?

Answer 4

• need to put adhesive on tray
• putty and alginate require different adhesives to be put on tray

Question 5

where do we put the putty and alginate adhesives?

Answer 5

• alginate adhesive want all over putty and tray
• putty adhesive only want on tray where you want putty

Question 6

do you mix impression materials before or after putting on adhesives

Answer 6

• brush adhesives onto tray BEFORE mixing impression materials or they will start to set before you can place them in mould

Question 7

how do we mix the putty?

Answer 7

• mix silicone putty and catalyst until all one colour
• use non-latex containing gloves

Question 8

1
where do we want to put the putty on the tray?

2
where do we not want putty on tray

Answer 8

1
- on palate area

• free end saddles
• large edentulous gaps
  any saddles that have a bigger
  gap than 1 molar or 2 pre-molars
  missing count as a large gap
  (small gaps do not need putty
  placed)

2
- teeth

• small edentulous areas/ gaps

Question 9

why do small edentulous areas not need putty placed?

Answer 9

• as will still be able to capture sulcus shape with alginate

CHECK IF CORRECT OR IF ANY OTHER REASONS WITH TUTOR

Question 10

1
why do we place putty on tray first

2
why do we need to place putty on palate?

Answer 10

1
- to modify the tray
- often doesn’t fit well
- thus will leave big gap between tray and tissues

• (we want putty in the bulky areas that may cause big gaps between tray and alginate so place putty so tray fits better)
• alginate will capture details of teeth

2
- to modify tray so it fits better as many people have high vaulted palate
- to capture shape as it will be joining everything together
- as may be uncomfortable if alginate goes there

Question 11

how do we remove any putty that has captured unwanted areas? (EG putty that has captured teeth impression or small gap?)

Answer 11

• we cut those areas with a scalpel
• when cutting teeth impressions away give approx 4 mm clearance

Question 12

when cutting putty around teeth area, why do we need to leave a little gap between putty and nearest tooth?

Answer 12

• give approx 4 mm clearance
• as important to capture impression around the tooth and tooth with alginate NOT putty
• as alginate impression will be more detailed

Question 13

what can you place on stock tray to make it more comfortable for patient?

Answer 13

• red ribbon wac around edge of tray

Question 14

why is it important to capture the retromylohyoid fossa with alginate?

Answer 14

this is a structure on the lower mandible

• want a detailed impression as this will help secure dentures with free end saddles

Question 15

what do primary and secondary denture support areas mean?

Answer 15

areas that support the denture

• Primary denture support areas DO NOT resorb with time
• Secondary denture support areas DO resorb with time

Question 16

mandibular primary denture support area

Answer 16

• buccal shelf

Question 17

maxillary primary support area

Answer 17

• Palate

Question 18

maxillary secondary support area

Answer 18

• alveolar ridge

Question 19

why is it important to know mandible resorption patterns when making RPD?

Answer 19

• need to know so we can think about this when designing dentures
• we use areas in the mouth for denture support
• want patients to be able to use dentures long term
• hence want to use areas of the mouth for support that have minimal resorption

Question 20

how much alginate powder do we use and how do we know how much to use?

Answer 20

• we use 2-3 scoops
• 3 scoops for maxillary impressions
• 2 scoops for mandibular impressions
  BUT for patients with bigger jaw may need to use 3

Question 21

how do we mix alginate?

Answer 21

• decide n.o scoops you will use on patient
• measure out corresponding water measurement
• scoop out alginate powder (do not need to powder in spoon) and level scoops
• fluff powder in bowl
• then add water in bowl
• stir
• then mix
• want to scrape against edge of bowl to remove air bubbles
• then scoop onto tray

Question 22

TIPS for using alginate

Answer 22

• wanna try and mix alginate and place in tray in less than 30 seconds
• use room temp water
• the hotter it is the quicker it will set

Question 23

what is putty made of?

Answer 23

silicone

Question 24

how do we mix the putty

Answer 24

• mix the silicone putty and catalyst until all one colour