PARTIAL DENT - Secondary Impressions

Question 1

what should be your position for upper impressions?

Answer 1

take from behind

Question 2

what should be your position for lower impressions?

Answer 2

from the front

Question 3

how should the patient be positioned when taking impressions?

Answer 3

• patients mouth above elbow height
• sat upright for lower
• slightly leaned back for upper - unless gagging

Question 4

how do you insert an impression tray?

Answer 4

• retract a corner of the mouth
• rotate the tray into the mouth
• seat posterior first and then anterior

Question 5

why is the posterior imp seated before the anterior?

Answer 5

it allows the excess imp to come forward instead of going down the throat

Question 6

how do you select the correct tray?

Answer 6

• box trays - for partial dentures
• curved trays - edentulous patients
• choose posterior width
• should be 2-3mm space buccal to the teeth

Question 7

how can a tray be adapted? and why?

Answer 7

use compound green stick or pink stick to add to a tray

or silicone putty

to build up to the sulcus if it falls short

Question 8

what is border moulding?

Answer 8

buccally
dentist taking hold of lips/cheeks
patient must be relaxed

lingually
patient makes tongue movements - lick the upper lip from one corner to another

Question 9

how do you take an alginate impression?

Answer 9

• load the tray
• insert, positon, seat
• border mould
• remove
• assess

Question 10

what are special trays?

Answer 10

made to reach parts that stock trays can’t

Question 11

what are special trays always used for and why?

Answer 11

definitive prosthetic impressions

• to record an accurate impression

Question 12

what material is used for acrylic?

Answer 12

light cured acrylics

Question 13

special trays can be made to have stops, why?

Answer 13

allow us to space the tray

• stops the tray in the area and reduces the pressure placed on the material.

Question 14

with special trays, where is it best to place the stops?

Answer 14

on teeth

but can be put on edentulous ridge for free end saddle

Question 15

what does it mean to space a tray?

Answer 15

it allows sufficient width of impression

so it can come out of undercut without tearing or distorting

Question 16

SO what’s the tray criteria for partial dentures?

Answer 16

• acrylic special tray
• spaced 3mm stops
• unperforated from the lab - can be perforated chairside
• handles not interfering with border moulding esp in the area of interest

Question 17

after designing and constructing a special tray in the lab, what’s the next step?

Answer 17

• check for sharp edges
• check for spacing/stops
• check border extension
• check handle not interfering with border moulding

Question 18

what does it mean when the tray moves too much whilst border moulding?

Answer 18

it is over-extended
- needs to be trimmed down

Question 19

what material is used to take a secondary impression?

Answer 19

heavy bodied silicone on the tray
light bodies silicone around the tooth

Question 20

describe the steps taking secondary impression for a partial denture

Answer 20

• select special tray
• line with adhesive
• load with medium bodied
• when halfway through filled, start placing light bodied around the tooth
• when tray is full, place mould into mouth
• border mould
• wait until medium bodied is fully set, usually wait for overset
• remove mould

Question 21

what can be used instead of heavy bodied silicone?

Answer 21

green stick

Question 22

after taking the impression, how is it transported?

Answer 22

• rinse under a tap
• disinfect with disinfectant or hypochlorite for 10 mins
• rinse again under tap
• if it is silicone, it needs to have a dry gauze wrap
• it is is alginate, it needs to have a damp gauze wrap
• place in a sealable bag