Dental Materials Lec 4 Impression Material

Front 1

What is the primary purpose of taking a dental impression?

Back 1

To make a negative reproduction of the dental arches.

Front 2

What tissues are included when making an impression?

Back 2

Existing teeth,
Restorations,
Hard & soft tissues (rugee, tori, Mx tubersity etc.)

Front 3

A diagnostic cast or "study model" forms a ________

Back 3

Positive replica of teeth and tissues.

Front 4

What material is a diagnostic cast made from?

Back 4

Plaster Stone.
(We don't make these at CCD, they're done in a lab or by a dental assistant.)

Front 5

A ________ model is what we work with and will be ground down in the lab.

Back 5

Working

Front 6

What is the purpose of a Dental Die?

Back 6

The lab can cut away the un-necessary elements and only work on those specific area. Like making a partial.

Front 7

A dental die is _________ than a study model/diagnostic cast.

Back 7

Softer

Front 8

What colors does a dental die usually come in?

Back 8

Yellow, blue or pink

Front 9

What state should impression material be so that it can adapt to teeth and tissues?

Back 9

A moldable or plastic state.

**The material then sets into a semi-solid or plastic state.**

Front 10

What are 6 important characteristics of impression material?

Back 10

1) Fluid enough to flow into or around area
2) Must harden once in the mouth
3) Must be biocompatible (won't harm tissues)
4) Dimensionally stable (won't expand/contract or change) 5) Easy to handle.
6) Able to disinfect.

Front 11

What is the purpose of impression trays?

Back 11

To carry impression materials to the mouth.

*Need to be able to invert, don't want' liquid goo*

Front 12

What are 2 other important aspects of impression trays?

Back 12

1) Support the material once its placed into the mouth
2) They need to be rigid enough to prevent distortion.

Front 13

What important feature must be part of either stock trays or custom-made trays?

Back 13

They need to be large enough to fit all of the oral structures.

Front 14

What is the purpose of the holes (perforations) in the impression trays?

Back 14

To create retention..the material locks into the tray because of the holes.

Front 15

When taking an impression for a partial, what do you take an impression of?

Back 15

Only the area that you need.

Front 16

Are metal impression trays perforated?

Back 16

Some are and some are not.

Front 17

If the metal trays aren't perforated, what needs to be done?

Back 17

You need to prime the tray with an adhesive.
It creates a sticky surface the material will adhere to rather than sticking to the teeth.

Front 18

What is a rim-lock in a metal impression tray?

Back 18

A raised or rolled edge that the material gets caught underneath and gets locked into the tray.

Front 19

What is the main difference between plastic & metal trays after the impression has been taken?

Back 19

Plastic are disposable.
Metal must be autoclaved but have to be prep'ed ahead of time
(They go in special cleaners to remove the residual material etc.)

Front 20

How do impression tray's come?

Back 20

Full uppers/lowers, Half right/left, Anterior only.

They don't have to be for the entire arch. Take the impression on what you need!

Front 21

Hydrocolloids

Back 21

A water based colloid that functions as elastic impression materials. (These are used in dentistry.)

Front 22

What are the 2 types of hydrocolloids?

Back 22

1) Reversible--Agar
2) Irreversible--Alginaties

Front 23

Which of these types of hydrocolloids do we NOT work with at CCD?

Back 23

Reversible

Front 24

What is the mechanism of actin on a reversible hydrocolloid?

Back 24

Water.
Warm water softens, Cool water hardens
**They are extremely accurate**

Front 25

The product used in a reversible hydrocolloid is called______-_______.

Back 25

agar-agar.
*Its from a seaweed extract.**

Front 26

What types of impression trays are used with a reversible hydrocolloid?

Back 26

Stock metal trays.
(The water tubing that goes through them allows for heating/cooling.)

Front 27

Irreversible hydrocolloid is also known as what?

Back 27

Alginate *It’s the most commonly used material.*

Front 28

What are 4 fabulous traits of alginate?

Back 28

1) Its inexpensive
2) Easy to use
3) requires no special equipment
4) numerous uses

Front 29

What are some uses of alginate that we'll work with as Dental Hygienists?

Back 29

Mouth guards
Custom fluoride trays
Diagnostic models,
Bleaching trays,
Partial denture frameworks,
Fabricate temporary restoratons

Front 30

What is the chemical composition of alginate?
(What ingredients at what %) MUST KNOW THIS!

Back 30

55% Diatomaceous earth (ground stone)
15-20% Potassium / sodium alginate (derived from seaweed)
14-20% Calcium sulfate dihydrate
10% Potassium Sulfate
2% trisodium phosphate

Front 31

What is the working time for regular-set alginates?
Fast set alginates?

Back 31

2-3 minutes (This is what we work with)
1.5-2 minutes

Front 32

When does working time begin?

Back 32

When the powder material and liquid combine.
*The longer one takes to mix the material, the less time one has to load and seat the tray.*

Front 33

What needs to be done to remove the impression from the mouth?

Back 33

Need to break the seal!
Use a rapid snap movement to decrease deforming or tearing.

Front 34

Once you remove the impression from the mouth what do you need to do?

Back 34

Keep it wet until (wrap in wet paper towel/keep in zip lock baggie) ready to pour up the impression in dental stone (gypsum)
**If its not kept moist the impression will shrink and it won't be accurate.**

Front 35

Before placing in a paper towel/zip lock baggie, what needs to be done to the impression?

Back 35

Rinse 1st (to remove any "lunch" debris, then disinfect (cavicide) it immediately!
(3 minute disinfection period)

Front 36

Ideally, when do you want to pour the impression to prevent distortion?

Back 36

1 hour of taking the impression

Front 37

Alginate that is mixed with too much water will be________.

Back 37

Weaker…more likely to tear and it will take longer to set!

Front 38

Removing the tray too slowly after the impression may cause the material to ________.

Back 38

Tear! Snap it out quickly.

Front 39

What are the 6 steps to the impression taking process?

Back 39

1) Select the proper tray size (might use different sizes on Mx vs Mn)
2) prepare the necessary materials.
3) Advise patient/patient comfort
4) consider work time/set time 3:00 minutes
5) Rinse after removal
6) Apply disinfectant

Front 40

If you select a tray that is not the correct size for the Pt, what do you do with the tray?

Back 40

Rinse, cavicide and place in zip lock bag…we'll recycle it.

Front 41

What can be done to a tray to make it wider? What if the tray needs to be extended?

Back 41

Heat it up

Wax can be added to the rims to extend the tray.

Front 42

What temperature of water is best to mix with the alginate?

Back 42

Cool or room temperature.

Front 43

What should I do with the can of alginate before opening and getting started?

Back 43

Tumble the can first!

Front 44

How much water gets mixed with each level scoop of powder?

Back 44

One scoop of water per water line.

Front 45

What must be work to avoid inhalation of powder?

Back 45

Masks!

Front 46

What color does our alginate begin as and what does it change to?

Back 46

Begins as purple, changes to pink and once its set its white.

Front 47

How do you remove air bubbles from the mix?

Back 47

Press it to the side of the bowl.

Front 48

Is manual mixing or mechanical mixing better?

Back 48

Mechanical, but we don't do this at CCD.

Front 49

How do you load the impression tray?

Back 49

Load from posterior and work to the anterior. Add large increments as quickly as possible. Smooth the surface with wet fingers and remove excess material.

Front 50

Which tray should you "seat" first and why?

Back 50

Lower tray first so as to avoid the gag reflex.

Front 51

When loading the lower tray, where should I be standing?

Back 51

In front of Pt. Apply equal pressure downward.

Front 52

When loading the upper tray, where should I be standing?

Back 52

Behind the Pt (at 11 or 1)
Seat the anterior of the tray 1st and then the posterior.

Front 53

What should I have the Pt do after loading the upper tray?

Back 53

Have Pt tilt head forward and provide them with paper towel.

Front 54

What is the regular set time vs fast set time?

Back 54

Regular: 2-5 minutes (once in the mouth) Fast set: 1-2 minutes (once in the mouth)

Front 55

What is considered an acceptable impression?

Back 55

All teeth and alveolar process is recorded
Good detail (including frenum)
No debris or distortion
Palatal vault is recorded
Retro-molar area/tuberosity is recorded

Front 56

Are dental impressions considered contaminated?

Back 56

YES! Remove, Rinse and disinfect.

Front 57

How long should the impression sit in a bag prior to pouring?

Back 57

3-30 minutes
(since placing cavicide on it, don't let it go past 30 mins)

Front 58

What is the purpose of the silicone bite impression?

Back 58

To "register" how the Pt's bite comes together.

Front 59

Gupsum is a material that is widly found…..

Back 59

in nature (They are mined and ground into a powder.)

Front 60

What 2 types of gypsym are we concerned with?

Back 60

Dihydrate & Hemihydrate
(The difference is in how much they are ground)

Front 61

If you're pouring a diagnostic model you should use _______.

Back 61

plaster (white) Very Porous

Front 62

If you're making a crown or bridge you use….

Back 62

Die stone (it can be cut apart)

Front 63

When hemihydrate is mixed with water it becomes a ___________ mixture.

Back 63

flowable

Front 64

When the impression is mixed with water, what type of reaction occurs in the bowl?

Back 64

Endothermic (Creates heat) *Double check this*

Front 65

What type of reaction happens when the material hardens? What is the material called?

Back 65

Exothermic..heat is give off and causes material to harden.

Front 66

When hemihydrate is heated in open vats to 115 C, what happens to the material?
What is the material called?

Back 66

It ends up very pourous and somewhat irrregular in its posered shape.
Plaster of B-hemihydrate (Beta-hemihydrate) Its white.

Front 67

If the hemihydrate is heated up under pressurized conditions at a temp > 115C what is the result of the powder particles?
What is the material called? What color is it?

Back 67

They are more uniform in shape, less pourous.
Dental Stone or Hemihydrate
Yellow

Front 68

If the temperature and pressure are further increased what is the material called?

Back 68

Die stone
It makes a more defined type model.

Front 69

What are 2 factors contribute to the strength & (abraision resistance) hardness of the model?

Back 69

Shape of the particles and porosity

Front 70

The strength of the gypsum products is related to the amount of _______ used to produce the study or working model.

Back 70

Water

Front 71

What does the difference in type of gypsom depend on?

Back 71

The size and shape of the particles,
The porosity of the powder, & they way the powder was processed.

Front 72

Physically, gypsum products are manufactured as? (3 items)

Back 72

Plaster, stone (yellow), and high-strength stone

Front 73

Larger, irregular particles make the product……?

Back 73

more porous and weaker. (Break & abrade easily)

Front 74

Smaller, more uniform particles make the product….?

Back 74

less porous and stronger
(Don't break as easily or abrade)

Front 75

___________ _________ happens with all gypsum products.

Back 75

Setting expansion

Front 76

Which product has the highest rate of expansion?

Back 76

plaster (white) Very Porous

Front 77

Which product has t he lowest rate of expansion?

Back 77

Die stone

Front 78

Set gypsum stone is not highly ________ in water?

Back 78

soluble

Front 79

Solubility is directly related to the ___________ of the material.

Back 79

porosity.
As such plaster is more more soluble than stone.

Front 80

Exposing models to ________ for a prolonged period of time should be avoided.

Back 80

water

Front 81

The mix that is created to take impressions should have sufficient _______ to reproduce details of the impression.

Back 81

Flow!

Front 82

Having too much water will make the mix _________

Back 82

weak (less accurate…needs to be like frosting.)

Front 83

Having too little water will make the mix _____ ______.

Back 83

not flow

Front 84

What is the mechanical device we can utilize to assist in mixing? What does it do?

Back 84

A Vibrator Gets rid of air bubbles

Front 85

When working with yellow lab stone, how do you want to add the water to the powder?

Back 85

Gradually.
Its easy to put in too much water and then you have to keep adding more stone

Front 86

What is the approximate working time of lab stone?

Back 86

About 5 minutes

Front 87

Diagnostic & working casts have two parts.
What are they?

Back 87

1) Anatomical portion (replicates the hard and soft structures)
2) The base or "Art Portion"

Front 88

What is the difference between a single pour and a double pour?

Back 88

A single pour fills the impression only (no base).
A double pour inverts the impressionon top of a "stone base"