Impression Materials

Question 1

iTero

Answer 1

Digital 3-D scanner
Can be used for Invisalign to make the trees
Also used for making crowns and bridges

Question 2

What is the function of impression materials?

Answer 2

To accurately record the dimensions of oral tissues and their spatial relationship to make a replica of the oral tissues

Gives you a negative reproduction, pour in stone or plaster to obtain the positive reproduction

Question 3

Properties for an ideal impression

Answer 3

Ease of manipulation 
Reasonable cost
Adequate flow properties 
Appropriate setting time
Good mechanical strength 
Dimensional accuracy 
Safe/non-toxic 
No degradation from disinfection 
Compatible w/other materials in the mouth
Lasts once opened

Question 4

Rigid/in elastic impression materials

Answer 4

Dental impression compound

Impression plaster

Zinc oxide Eugenol (for edentulous patients)

Question 5

Flexible/Elastic impression materials

Answer 5

Alginate hydrocolloid

Agar hydrocolloid

Elastomeric/rubber impression materials

Question 6

3 types of elastomeric dental impression materials

Answer 6

Polysylfide, silicone and polyether

Question 7

2 types of dental impression compound

Answer 7

Tray compound

Impression compound

Question 8

Tray compound

Answer 8

Used to prepare a custom made preliminary impression or tray that will record the final impressions (holds impression materials)

Red wax

Made of resin, waxes, organic acids, coloring and fillers like talc and chalk

Question 9

Impression compound

Answer 9

Commonly used to take a final impress of a tooth prep and help check the accuracy of the prep

Question 10

Manipulation of tray compound

Answer 10

Must soften and then place in mouth to form or can already be in the shape of an arch

Rubber impression material will go in that tray to take the impression

Question 11

Manipulation of impression compound

Answer 11

Principle indication for this material is for a “check impression”.

A stick of the material is heated and then is allowed to flow into impression and held until it cools and sets

Question 12

Alginate Hydrocolloid

Answer 12

Originates from seaweed and kelp

When mixed becomes and irreversible gel

One of the most widely used dental impression materials

Question 13

Why is alginate hydrocolloid one of the most widely used impression materials?

Answer 13

Easy to mix and manipulate

Minimum equipment necessary

Flexibility of impression

Accuracy of impression

Low cost

Question 14

Manipulation/mixing systems

Answer 14

Two-paste type

Manipulation

Question 15

Two-paste type

Answer 15

Equal lengths and mixed

OR

automatic mixing system— show fewer voids, very fast and easy to use. Mix is perfect

Question 16

Manipulation

Answer 16

Put equal lengths and mix homogeneously

Setting time can be altered by increasing the temperature

Question 17

Wax bite registration

Answer 17

Use a wax bite to record patients bite

Must always have a wax bite with each study model/cast

Question 18

Snap-set

Answer 18

Transition from plastic condition into elastic properties

Question 19

Dimensional change

Answer 19

Expand in water or shrink out of water

All materials will shrink due to polymerization

Question 20

Elastic recovery

Answer 20

Happens when you remove impression from the mouth

Question 21

Flow

Answer 21

Silicones and polyethers have the lowest flow and polysulfides have the highest

Question 22

Tear strength

Answer 22

Indicates what the material can withstand

Question 23

Dies

Answer 23

Are another method for taking an impression

Question 24

Imbibition

Answer 24

When a gel or solid blabsorbs liquid resulting in the swelling of material

Question 25

Composition of alginate

Answer 25

``` Diatomaceous earth Calcium sulphate Sodium or potassium triethanolamine alginate Zinc oxide Potassium titanium fluoride Sodium phosphate Coloring/flavoring ```

Question 26

ANSI- American National Standards Institute

Answer 26

Global and they have standards in place for nuclear, electrical, construction etc. ADA specification #18, odor, flavor, irritation, etc

Question 27

Two types of alginate

Answer 27

Type I- fast setting 1-2 min Type II- normal set, 2-5.5 min Alginate turns colors as it is setting

Question 28

How to alter alginate setting times

Answer 28

Cooler water increases setting time Warmer water decreases setting time

Question 29

Objectives for taking an alginate impression

Answer 29

All teeth are included Entire alveolar process Retromolar area must be present Maxillary tuberosity present Detailed, undistorted and bubble free production of the oral tissues

Question 30

Proper form for maxillary alginate tray

Answer 30

Completely cover maxillary tuberosity Be 4mm wider than the most apical portion of the alveolar process at the mole region Cover the anterior teeth with the incisors contacting the flat arch portion of the tray about 4mm from the raised palatal part of the tray

Question 31

Proper form for mandibular alginate tray

Answer 31

Cover all teeth and retromolar pad Be 4mm wider than the buccal and lingual positions of the posterior and labial and lingual positions of the anterior teeth Allow the teeth to be centered and yet comply with 2 and 3 from maxillary steps

Question 32

How to handle the impression

Answer 32

Rinse with cool water Cut away unsupported alginate Disinfect with caviwipe Wrap in caviwipe and place in a head rest cover Impression must be poured within an hour

Question 33

Troubleshooting alginate setting too soon:

Answer 33

Maybe incorrect powder to water ratio High room temp Too much time mixing and/or loading tray