Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
94 Cards in this Set
- Front
- Back
|
What is the term for a dimensionally accurate reproduction (replica) of the hard and/or soft oral tissues that is used primarily for observation or record purposes?
|
Model
|
|
|
What is the term for a reproduction of the oral tissues used as a working model?
|
Cast
|
|
|
What is the term for a working reproduction of a single tooth or several teeth, on or within which prostheses are constructed?
|
Die
|
|
|
A (cast/die) is only a reproduction of a few teeth, not ALL teeth
|
Die
|
|
|
What are the big 6 main purposes of models, casts, and dies?
|
1. Fabricate crowns, bridges, inlays, onlays
2. Fabricate complete dentures 3. Fabricate removable partial dentures 4. Fabricate frame-works for dental implants 5. As study models (diagnostic casts) 6. Fabricate ortho appliances |
|
|
You tell your lab tech that they can use either gypsum or epoxy to create a cast out of a certain impression. The impression material would NOT be:
A. polysulfide B. polyethers C. alginate D. addition silicones E. condensation silicones |
C. alginate
alginate and agar are only compatible with gypsum! (see page 2, slide 6) |
|
|
According to ANSI/ADA spec # ___, there are ___(#) types of gypsum products
|
25, 5
|
|
|
Type __ gypsum product is impression plaster and rarely used in dentistry
|
1
|
|
|
Type __ gypsum product is model plaster and used for study casts, record purposes, and ortho models
|
2
|
|
|
Type __ gypsum product is dental stone (or model stone) and is used for full arch casts and investing dentures
|
3
|
|
|
Type __ gypsum product is dental stone, high strength (die stone) and used for high-noble and noble casting alloys
|
4
|
|
|
Type __ gypsum product is dental stone, high strength, high expansion and used primarily for base metal casting alloys
|
5
|
|
|
Which type of gypsum product (#) is used for edentulous arches?
|
1
|
|
|
Which type of gypsum product (#) is used for ortho models?
|
2
|
|
|
Which type of gypsum product (#) is used for investing dentures?
|
3
|
|
|
Which type of gypsum product (#) is used for high noble castings?
|
4
|
|
|
Which type of gypsum product (#) is used for base metal casting?
|
5
|
|
|
True or False, each gypsum product has a unique chemical equation
|
False! They are all the same! (CaSO4 x 1/2 H2O)
|
|
|
What is different about the composition of each gypsum product?
|
they have crystals of different shape, size, and porosity depending on method of manufacture
|
|
|
Model (or dental) plaster is also known as ___
|
beta-hemihydrate
|
|
|
Model (dental) plaster is produced by heating gypsum in (a vacuum/open air) at ___C
|
open air, 115C
|
|
|
What is the water powder ratio (mL to g) for model plaster?
|
50mL/100g
|
|
|
Dental stone is also known as what?
|
alpha-hemihydrate
|
|
|
dental stone is made by heating gypsum (in air/under pressure) at ___C
|
pressure, 125C
|
|
|
Which of these is heated under pressure?
A. beta-hemihydrate B. alpha-hemihydrate C. alpha-modified-hemihydrate |
B. alpha-hemihydrate
|
|
|
What is the water/powder ratio (mL to g) of dental stone?
|
30mL/100g
|
|
|
high strength dental stone is also called what?
|
alpha-modified-hemihydrate
|
|
|
high strength dental stone is made by boiling gypsum in __% aqueous solution of CaCl2 and __Cl2
|
30%, Mg
|
|
|
dental stone is (more/less) porous than model plaster and has uniformly shaped crystals
|
less
|
|
|
High strength dental stone has (loose/dense) crystals that are ___ in shape
|
dense, cubic or rectangular
|
|
|
What is the water/powder ratio (mL to g) of high strength dental stone?
|
23mL/100g
|
|
|
What is the purpose of grinding hemihydrate particles?
|
to eliminate needlelike particles and improve packing characteristics
|
|
|
What can be added to reduce water requirements of gypsum products?
|
surface-active materials (gum arabic with calcium carbonate)
|
|
|
The setting reaction for gypsum products is (exothermic/endothermic/neutrothermic)
|
exothermic
|
|
|
To create the plaster or stone that is packaged for use, the manufacturing process begins with gypsum and (cools/heats) it to get the final product.
|
heats
|
|
|
In the setting reaction for gypsum, hemihydrate dissolves until it forms a ___ solution
|
saturated
|
|
|
When hemihydrate is mixed with water, a suspension is formed that is (fluid/solid)
|
fluid
|
|
|
With gypsum setting, there are 2 so called "setting times". The first is about __ min while the second is __ min
|
3, 15
|
|
|
The initial setting is over when the gypsum (loses gloss/becomes glossy)
|
loses gloss
|
|
|
The time from mixing until mix is firm is the (initial/final) setting time
|
initial
|
|
|
True or False, altering W/P ratio is an acceptable way to alter setting time
|
False, do NOT do this
|
|
|
As W/P ratio increases, setting time (increases/decreases)
|
increases (they go up and down together)
|
|
|
As W/P ratio increases, strength and setting expansion (increases/decreases)
|
decreases
|
|
|
True or False, W/P ratio is different for different gypsum products
|
True
|
|
|
Which of these W/P ratios will have the LONGEST setting time?
0.3 0.4 0.5 |
0.5
high W/P = longer time |
|
|
What is the best way to alter setting time?
|
The temperature of the water used (hotter = longer setting)
|
|
|
At what temperature is water so hot that no reaction occurs with gypsum products?
|
> 100C
|
|
|
Accelerators (increase/decrease) the rate of the chemical reaction and this (lengthen/shorten) working time
|
increase, shorten
|
|
|
Retarders (increase/decrease) rate of chemical reaction and thus (shorten/lengthen) working time
|
decrease, lengthen
|
|
|
gypsum slurry can be used as what?
|
an accelerator
|
|
|
Why are accelerators not recommended?
|
they alter the composition of the gypsum
|
|
|
What can be used as accelerators? (name 3)
|
K2SO4, NaCl (>20%), gypsum particles
also, gypsum slurry |
|
|
Blood and salvia are examples of (accelerators/retarders)
|
retarders
|
|
|
NaCl 28% is (accelerator/retarder)
|
retarder
|
|
|
Potassium citrate is (accelerator/retarder)
|
retarder
|
|
|
If temp of water is less then 37C, the setting time (increases/decreases)
|
decreases
|
|
|
Longer and faster spatulation results in (longer/shorter) setting time
|
shorter
|
|
|
(mechanical/manual) spatulation results in fewer bubbles
|
mechanical
|
|
|
(larger/smaller) particles harden the mix faster
|
smaller
|
|
|
Spatulating quickly tends to (increase/decrease) setting time
|
decrease
|
|
|
With more water, you get (more/less) volumetric expansion
|
more
|
|
|
what is the range for setting expansion of model plaster (in air)?
|
0.2-0.3% (MAX: 0.3%)
|
|
|
what is the range for setting expansion of dental stone (in air)?
|
0.08-0.1% (MAX: 0.2%)
|
|
|
what is the range for setting expansion of improved stone (in air)?
|
0.05-0.07% (MAX: 0.1%)
|
|
|
Hygroscopic expansion is more than twice the normal setting (contraction/expansion)
|
expansion
|
|
|
Rank these in terms of the STRONGEST to WEAKEST dry strength
type 5 type 4 type 3 type 2 |
They are already in the right order! Strength is highest with type 5, worst with type 2, in that order.
|
|
|
Dry strength is usually (half/double) the wet strength
|
double
|
|
|
wet strength is the same as ___ strength
|
green
|
|
|
High W/P ratio = (high/low) dry strength
|
low
|
|
|
Accelerators and retarders tend to (lower/raise) strength
|
lower
|
|
|
If an impression material is very wettable, then the cast will tend to have (fewer/more) bubbles
|
fewer (more wettable = less bubbles)
|
|
|
If stone has a high contact angle on a particular impression material, then it will have relatively (more/less) bubbles
|
more (remember, high contact angle means POOR wettability... poor wettability = more bubbles)
|
|
|
If a stone has many air bubbles, it will be (stronger/weaker) than a stone with less air bubbles
|
weaker
|
|
|
Mmmmmmk?
|
Mmmmmmk.
|
|
|
High W/P ratio = (higher/lower) wet strength
|
lower
|
|
|
Gypsum hardener is used in (addition to/place of) water
|
in place of. usually 20% gypsum hardener, 80% water (as opposed to 100% water)
|
|
|
The tendency of a material to absorb water from the air is called its "____" property
|
hydroscopic
|
|
|
You can disinfect gypsum casts with ___ or 1:10 sodium hypo___
|
iodophor, chlorite
|
|
|
You can sterilize cases overnight with __ if the patient is known to have an infection
|
gas
|
|
|
Ortho plaster is a mix of what two other types of gypsum products?
|
model plaster and dental stone
(mounting plaster and mounting stone) |
|
|
True or False, Epoxy Dies are not gypsum products
|
True
|
|
|
Epoxy dies are (weaker/tougher), have (lower/higher) compressive strength, and are (more/less) abrasion resistant than high-strength die stones
|
tougher, higher, more
|
|
|
Epoxy dies are (harder/softer), (more/less) accurate, and (more/less) dimensionally stable than high-strength stone dies
|
softer, less, less
|
|
|
Epoxy dies have (high/low) viscosity
|
high (thus, they get porosities easily)
|
|
|
Epoxy dies undergo setting (contraction/expansion) of 0.03-__%
|
contraction, 0.03-0.30%
|
|
|
Epoxy can be poured into which 3 impression materials?
|
silicone (addition and condensation)
polyether polysulfide |
|
|
Epoxy dies contain a resin (monomer/polymer) and a poly___ hardener
|
monomer, polyamine
|
|
|
The (monomer/hardener) is toxic and allergenic in epoxy dies
|
hardener
|
|
|
(gypsum/epoxy) has better abrasion resistance
|
epoxy
|
|
|
(gypsum/epoxy) is easier to work with
|
gypsum
|
|
|
(gypsum/epoxy) requires more time
|
epoxy
|
|
|
(gypsum/epoxy) is compatible with more impression products
|
gypsum
|
|
|
(gypsum/epoxy) undergoes expansion
|
gypsum
|
|
|
(gypsum/epoxy) has a higher potential for allergic reactions
|
epoxy
|
