Preliminary Impressions

Question 1

impression materials include (2)

Answer 1

inelastic/rigid

elastic (elastomers, elastomeric)

Question 2

inelastic/rigid (4)

Answer 2

plaster
zinc oxide eugenol
impression compound
wax

Question 3

elastic (elastomers, elastomeric) (4)

Answer 3

hydrocolloids
polysulfides
polyethers
silicones

Question 4

land area

Answer 4

defines limits of your impression (flat area)

Question 5

base is no more than – mm

Answer 5

15 mm

Question 6

irreversible hycrocolloid is known as

Answer 6

alginate

salts of alginic acid

Question 7

what composes irreversible hydrocolloid? (6)

Answer 7

60% diatomaceous earth
16% calcium sulfate 
15% potassium alginate 
4% zinc oxide
3% K titanium fluoride 
2% sodium phosohate

Question 8

diatomaceous earth

Answer 8

a filler which increases strength and stiffness and produces a smooth texture

Question 9

types of impression trays (2)

Answer 9

stock: various sizes and materials
custom: fabricated on patients cast

Question 10

add — — to the periphery of the stock trays prior to the impression

Answer 10

rope wax

Question 11

steps of maxillary alginate impression (9)

Answer 11

1. size correct tray; modify borders with wax if needed
2. have patient wipe palate with gauze to remove viscous saliva
3. mix 45 s
4. load tray and set aside
5. preload palatal vault with material
6. seat impression tray while retracting lips/cheeks to prevent trapping air in vestibules
7. hold tray still for 3 min
8. remove in 1 firm motion
9. inspect, rinse, disinfect w contact time of 10 min

Question 12

max preliminary impression should include (7)

Answer 12

residual ridge 
buccal and labial vestibules 
frenal attachments 
fovea palatinae and vibrating line 
palate tuberosities
hamular notches

Question 13

mandibular alginate impression steps (8)

Answer 13

1. patient in upright position
2. size tray
3. powder and room temp water
4. mix, load tray, set aside
5. preload buccal vestibules
6. partially seat tray in mouth, patient lifts and protrudes tongue slightly, seat tray further
7. close halfway, pull lip out slightly to free trapped air
8. seat and hold for 3 min, remove, inspect, rinse, disinfect

Question 14

mandibular impression should contain (8)

Answer 14

residual ridge 
retromolar pads
buccal shelf areas
external oblique ridges 
frenal attachments
retromulohyoid spaces
alveololingial sulcus 
labial and buccal vestibules