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BDS2 CLINICAL Dental Materials > Impression Materials > Flashcards

Flashcards in Impression Materials Deck (74)
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1

What is the function of impression materials

To produce an accurate replica of the surface and shape of hard and soft oral tissues

2

What is an impression

a negative reproduction of tissues

3

What is dental stone used to do

fill impressions to produce a positive replica (stone cast) which represents the position, shape, size and orientation of each tooth

4

What are dental stone casts used for

evaluating dentition when orthodontic, occlusal or other problems involved
in laboratory fabrication of restorations and prostheses

5

What does the treatment properties hinge on

the quality and accuracy of the initial impression

6

What does the impression material require

Impression materials with the right properties
clinician with good technique

7

What are the classifications of impression materials based on

Clinical
Properties

8

What are the clinical classification

mucostatic
mucocompressive

9

What are the properties

elastic
non elastic

10

What are mucostatic impression materials

zinc oxide eugenol, low viscosity alginates

11

What do mucostatic impression materials do

fluid materials that displace the soft tissues slightly
give an impression of the undisplased mucosa

12

What are mucocompressive impression materials

impression compound
high viscosity alginates
elastomers

13

What do mucocompressive materials do

viscous materials that record an impression of the mucosa under load i.e give an impression of displaced soft tissues

14

What happens to the impression material during removal

it undergoes elastic strain and has to change shape to overcome the bulbosity of the tooth

15

What do we want the impression material to do after removal

change back to its original shape making it truly elastic

16

What is it called when the impression material never returns to its original shape

permanent strain
it does not recover
making the impression inaccurate

17

What should be done to try and decrease the permanent deformation

keep the load time less by removing with a sharp pull so there is less overall permanent strain

18

What are the two types of elastic materials

hydrocolloids
elastomers

19

What are the elastomers

polysulphides
polyethers
silicones

20

What are the hydrocolloids

agar (reversible (lab duplicating) but no longer used
alginate - irreversible

21

What are the elastomers

polysulphides
polyethers
silicones (conventional and addition cured)

22

What happens to non elastic material on removal

don't recover well
either deform/fracture

23

What is the impression process

preparation
insertion
setting
removal
storage
cast prep

24

What happens in preparation

mixing
chemical reaction
heat
to result in a material that slows and takes up shape/space available

25

What happens in insertion

pick a tray
need adhesive maybe

26

What happens in setting

chemical
polymerisation
cooling (only some)
to form a solid replica

27

What happens in storage

need to see how quickly the impression needs to be poured before the dimensional changes become significant
but should wait a bit to allow elastic recovery

28

What are the ideal properties needed for

accuracy
patient
operator

29

What are the properties for accuracy

flow
setting changes
removal
storage
decontamination
compatible with cast material
viscosity
setting mechanism
thermal expansion coefficient
hydrophobic/hydrophilic
elasticity
tear strength

30

What is the ideal property for flow

that it can flow over the dentition and make intimate contact with the surfaces and record surface detail