Gypsum Flashcards
Gypsum Materials
Mineral - gypsum (__________)
___ ____ ____ ____
____ or ____
Mostly ___ but they do make some synthetic
Foundation of all the dental stones you will use
Gypsum Materials
Mineral - gypsum (CaSO4 2H2O)
calcium sulfate di-hydrate
Mined or synthetic
Mostly mined but they do make some synthetic
Foundation of all the dental stones you will use
____ of gypsum into ___ is accomplished by____ ____ gypsum to _______ degrees C.
How they take it from mined rocks and make it to a usable plaster
This is just heating crushed gypsum
To get the diff types of dental stones depends on what you do when you calcinate the gypsum
Calcination of gypsum into plaster is accomplished by heating crushed gypsum to 110-120 degrees C.
How they take it from mined rocks and make it to a usable plaster
This is just h eating crushed gypsum
To get the diff types of dental stones depends on what you do when you calcinate the gypsum
__________ + _____ <–> ______ + _____
( Gypsum ) ( Dental Plaster –
calcium sulfate___ ____)
Calcination ____ will determine type of plaster formed.
If you just __ ___ you get Plaster of Parisà Ortho, not very strong
If you ___ ___ with ____ you get Model Stoneà Diagnostic Cast
If you___ ___ with____ you get Die Stone
CaSO4 . 2H2O + Heat D CaSO4.1/2H2O + 11/2H2O
( Gypsum ) ( Dental Plaster –
calcium sulfate hemi-hydrate)
Calcination environment will determine type of plaster formed.
If you just heat it you get Plaster of Parisà Ortho, not very strong
If you close Kettle with Steam you get Model Stoneà Diagnostic Cast
If you close Kettle with CaCl2 you get Die Stone
Types of Gypsum
Type 1 -
Type 2 -
Type 3 -
Type 4 -
Type 5 -
Types of Gypsum
Type 1 - Impression plaster
Type 2 - Model plaster
Type 3 - Dental stone
Type 4 - High-strength dental stone (low expansion)
Type 5 - High-strength dental stone (high expansion)
Chemical Formula
_________ - The chemical formula is the same for all 5 types of ___ ___
Calcium sulfate hemi-hydrate
Chemical Formula
CaSO4 1/2H2O - The chemical formula is the same for all 5 types of dental stone.
Calcium sulfate hemi-hydrate
Chemical Reaction
Plaster/ Die stone Set Gypsum
CASO4 1/2H2O + water à CaSO4 2H2O +heat
This reaction accompanied by:
1) evolution of heat- exothermic reaction
2) development of strength
3) setting expansion
The way the stone sets is thru a crystalline growth procedure so you get expansion
Chemical Reaction
Plaster/ Die stone Set Gypsum
CASO4 1/2H2O + water à CaSO4 2H2O +heat
This reaction accompanied by:
1) evolution of heat- exothermic reaction
2) development of strength
3) setting expansion
The way the stone sets is thru a crystalline growth procedure so you get expansion
Excess Water
Excess Water, mL/100 g
Model plaster ____
Dental stone 9-13
HSDS ____
This is water trapped in the ___ ___ ___
The one that packs together nicely has less water
Excess Water
Excess Water, mL/100 g
Model plaster 18-31
Dental stone 9-13
HSDS 0-5
This is water trapped in the inter-crystalline spaces.
The one that packs together nicely has less water
Properties
ANSI/ADA Spec. 25 - certified products
Quality – ____ and free of ___ ___ and ___
____ at pouring (type ___ only)
Setting Time – type I ____ min., all other types of stone within ___% of manufacturer’s claim
Linear setting Expansion –
I : 0-___%
II : 0-___%
III : 0-___%
IV : 0-___%
V : ___-0.__%
Fracture (type ___ only) – Must break ___ and be able to be___
Compressive strength-
I : 4.0 MPa min. 8.0MPa max.
II : 9.0 MPa min.
III : 20.0 MPa min.
IV : 35.0 MPa min.
V : 35.0 MPa min.
Reproduction of ___
Most people don’t use Type I (for impressions) anymoreà Now we use other impression materials
Properties
ANSI/ADA Spec. 25 - certified products
Quality – uniform and free of foreign matter and lumps
Fluidity at pouring (type I only)
Setting Time – type I 2.5-5.0 min., all other types of stone within 20% of manufacturer’s claim
Linear setting Expansion –
I : 0-.15%
II : 0-.30%
III : 0-.20%
IV : 0-.15%
V : 0.16-0.30%
Fracture (type I only) – Must break cleanly and be able to be reassembled
Compressive strength-
I : 4.0 MPa min. 8.0MPa max.
II : 9.0 MPa min.
III : 20.0 MPa min.
IV : 35.0 MPa min.
V : 35.0 MPa min.
Reproduction of detail
Most people don’t use Type I (for impressions) anymoreà Now we use other impression materials
Properties
Compressive strength -____ > ___ >___
Tensile strength - very ___ on all of them
Abrasion resistance - __> __>___
Setting time – __ to ___ min
That is the initial set
That is not the time you need to leave it in the impression before you pull it out
Don’t rush separation
Setting expansion ___ ____ ___ ____ _____
Important for precision fits
Properties
Compressive strength - HSDS>DS>MP
Tensile strength - very low on all of them
Abrasion resistance - HSDS>DS>MP
Setting time – 8 to 16 min
That is the initial set
That is not the time you need to leave it in the impression before you pull it out
Don’t rush separation
Setting expansion IP=HSDS<ds></ds>
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Manipulation Affects Set
Spatulation time
An____ in mix time, gives a ____ in set time
If you hand mix as you spatulate longer the set time goes down
When you mechanically and vacuum spatulate the time goes down much ____
Manipulation Affects Set
Spatulation time
An increase in mix time, gives a decrease in set time
If you hand mix as you spatulate longer the set time goes down
When you mechanically and vacuum spatulate the time goes down much quicker
Manipulation Affects Set
Water temperature
As temperature increases, set time____, to a point, then begins to ____ again
Warmer waterà Faster Set
However if it gets too hot (past _____) it goes backwards (setting time will increase)
100F is not that hot (just warm)
If you are going to use hotter water, use warm water not hot hot water
At ____ , _____ of ___and ____ are ____, therefo ___ ___
Boiling Water
Manipulation Affects Set
Water temperature
As temperature increases, set time decreases, to a point, then begins to increase again
Warmer waterà Faster Set
However if it gets too hot (past 100F) it goes backwards (setting time will increase)
100F is not that hot (just warm)
If you are going to use hotter water, use warm water not hot hot water
At 100oC solubility of dihydrate and hemihydrate are equal, therefor No Set
Boiling Water
Manipulation Affects Set
Humidity during storage
Early- ____, Late- ____
Open stone storage container
Gypsum is very sus to absorbing moisture from the atm
As it absorbs water early on you get a decrease in your set time
As it gets more water and starts to reach the point of saturation, the set time increases and eventually it will get to the point where it will not __ at ___
____ systems – ___, ___, ___
All act as ____ of Set
Poison the ___ ___ ___
If you take an impression and patient bled into it, this will keep your stone from setting
Hydrocolloid systems means alginates
Need to wait to separate it
Manipulation Affects Set
Humidity during storage
Early- Decreases, Late- Increases
Open stone storage container
Gypsum is very sus to absorbing moisture from the atm
As it absorbs water early on you get a decrease in your set time
As it gets more water and starts to reach the point of saturation, the set time increases and eventually it will get to the point where it will not set at all.
Colloidal systems – hydrocolloid, saliva, blood
All act as retarders of Set
Poison the crystalline matrix nuclei
If you take an impression and patient bled into it, this will keep your stone from setting
Hydrocolloid systems means alginates
Need to wait to separate it
Manipulation: Water: Powder Ratio
W/P ratio – affects the ___, ___, ___
Use slurry water instead of distilled water:
Use Gypsum Hardener instead of Distilled Water:
Increase the Mixing Time:
Mixing under Vacuum:
Use extra water: Increase
Manipulation: Water: Powder Ratio
W/P ratio – affects the consistency, expansion, strength
Use slurry water instead of distilled water: Shorter Set Time, Lower compressive Strength, Higher Setting Expansion
Use Gypsum Hardener instead of Distilled Water: Higher Compressive Strength, Higher Setting Expansion, Higher Fluidity
Increase the Mixing Time: Shorter Set Time, Higher Compressive Strength, Increase Expansion, Lower Fluidity
Mixing under Vacuum: Higher Strength, Higher Fluidity
Use extra water: Increase Set Time, Lower Compressive Strength, Lower Expansion, Higher Fluidity
Manipulation
Surfactants & vibration - ___ ____
Surfactant=Debubblizer
Spray it on impression
Reduces ___ ___ and lets you get a better ___
If you use too much of it and allow it to pool up, you will get a billion ____s in your stone.
Spray lightly and then use __ ___ to blow the excess out
Immersion in ___ during set - ___ in expansion (___ expansion)
Hydroscopic: you poured it up and then immediately put it into a water bath
Hardening solutions – typically a ___% ___ solution
Increase the surface hardness but ___ ___ is not necessarily improved
Usually causes ___ expansion
Manipulation
Surfactants & vibration - reduce bubbles
Surfactant=Debubblize
Spray it on impression
Reduces Surface Tension and lets you get a better pour
If you use too much of it and allow it to pool up, you will get a billion microbubbles in your stone.
Spray lightly and then use air syringe to blow the excess out
Immersion in water during set - increase in expansion (hygroscopic expansion)
Hydroscopic: you poured it up and then immediately put it into a water bath
Hardening solutions – typically a 30% silica solution
Increase the surface hardness but abrasion resistance is not necessarily improved
Usually causes increased expansion
Chemical Modifiers
Accelerators - Decrease the set time
___ - Most common, ___ concentration
___- ___ concentration
Retarders – Increase the set time
___ – __ concentration
___, ___ ___
Found in alginate
___- > ___ concentration
Most also affect strength and expansion
Chemical Modifiers
Accelerators - Decrease the set time
K2SO4 - Most common, any concentration
NaCl - < 5% concentration
Retarders – Increase the set time
Borax – Any concentration
Agar, gum Arabic
Found in alginate
NaCl - > 20% concentration
Most also affect strength and expansion
Setting-expansion inhibitors (Decrease Expansion)
___
___
____
Setting-expansion inhibitors (Decrease Expansion)
K2SO4
KCL
potassium tartrate
Power-Driven Vacuum Mixing
Less ____
Increased ____
Power-Driven Vacuum Mixing
Less bubbles
Increased strength
Packaging
Bulk – ___ ___ or ____
Have to keep this covered properly!
Cheaper
Pre-packaged ____
$$$$$$
Pre-packaged __ and ___ system
Packaging
Bulk – Bags, boxes or buckets
Have to keep this covered properly!
Cheaper
Pre-packaged envelopes
$$$$$$
Pre-packaged mix and toss system
Die Materials
___
Type __
Type __
____
What you use to wax on to create a dental restoration (Patient takes their tooth home with them so you need a replica of it)
Die Materials
Gypsum
Type IV
Type V
Epoxy
What you use to wax on to create a dental restoration (Patient takes their tooth home with them so you need a replica of it)
fg,32Die Materials-Gypsum Type IV
All type IV die materials are high ___/low ___
There are three types of Type IV material: ___ gypsum, __ ___ gypsum and ___
Setting expansion _____% ADA specification 25 section 5.4
Die Materials-Gypsum Type IV
All type IV die materials are high strength/low expansion.
There are three types of Type IV material: regular gypsum, resin fortified gypsum and scannable.
Setting expansion 0% - 0.15% ADA specification 25 section 5.4
