Gypsum Stone
Materials
True/False
Setting Time
100
True or False: The desirable strength of gypsum material is directly related to the amount of water used.
Answer: True
The higher the water: Powder ratio, as in plaster, the softer and weaker the resulting gypsum product will be.
100
Milhouse is getting braces. Ortho office took impressions of his maxillary and mandibular arches. The replica made from each impression to discuss the treatment plan is termed as_____ _____?
Answer: Study Model
--Used for observation, diagnosis, and treatment plans.
100
True or false regarding Gypsum Materials:
Statement: They are synthetic materials.
Answer: False
-Made of stone, gypsum rock which are minerals found in various parts of the world.
100
1. ____ time or Initial Setting time- start of the mix, can be manipulated, partial progress of setting is occurring.
2. ____ setting time represents the length of time from start of the mix until the setting becomes rigid and can be separated from the impression. Completion of the hydration reaction.
Answer: 1. Working time
Answer: 2. Final Setting time
200
Examples of gypsum products are:
-Plaster
-Stone
-High strength or improved stone
200
Positive reproduction of a SINGLE TOOTH is used to fabricate an indirect restoration is called ____.
Answer: DIE
-It is a cast used in the construction of a Crown.
200
True or false regarding Gypsum Materials:
Statement: They can be used as impression materials.
Answer: True
-Material used for pouring impression.
200
Example of how to increase the setting times of gypsum products:
Define Increase setting time= Slow down setting time, give you more time to work.
Increase Setting Time (Slow ST)
- Decrease mixing - because not all the surfaces of the particles will be wet and interact with the water
- Increase water: powder ratio - creates a thinner mix
- Addition of retarders (borax)
- Cold water temperature
300
What is gypsum?
Microstone fine powder that is mixed with water to form a slurry, which can be poured and shaped. That later hardens into a rigid, stable mass.
300
A _____ is a replica on which a restoration or appliance is fabricated. Can be a replica of a quadrant, more than one tooth, or a full arch.
Answer: Cast
300
True or false regarding Gypsum Materials:
Statement: They can be used for diagnostic casts.
Answer: True
-Cast is replica on which a restoration or appliance is made/fabricated. A cast is more accurate than a study model, more than one tooth, an arch, or a quadrant.
300
Example of how to decrease the setting times of gypsum products:
Define Decrease setting time= Speed up setting time, give you less time to work.
Decrease Setting Time (Fast ST)
- Increase mixing (the longer the mixing time, the shorter the setting time).
- Decrease water: powder ratio - creates a thicker mix
- Addition of accelerators (potassium sulfate)
- Warm water temperature
- Mixing in a contaminated bowl
400
Weakest to strongest Gypsum:
1. Plaster- First gypsum product available. Weakest and cheapest. Sometimes referred to as Type II plaster.
2. Stone- More regular, uniform in shape, stronger than plaster.
3. High Strength or Improved Stone- Strongest, calcining gypsum in chloride solution.
400
Plaster or stone is obtained from gypsum by removing water by heat.
What is this process called?
Answer: Calcination
400
True or false regarding Gypsum Materials:
Statement: They are used in the fabrication of ceramo-metal restorations.
Answer: True
Ceramo-Metal restoration- are porcelain bonded to metal or porcelain fused to metal crowns.
400
An example of how to decrease the setting time of gypsum is
A. Using more powder and less water
B. Using more water and less powder
C. Using colder water
Answer: A. Use more powder and less water
500
Desirable properties of gypsum products: Pg.131 in book
Answer: Name at least 2: Pg. 131 in book
1. Accuracy
2. Dimensional Stability
3. Ability to reproduce fine detail
4. Strength and resistance to abrasion
5. Compatibility with impression material
6. Color
7. Biological Safety
8. Ease of use
9. Cost
500
This type of restoration is fabricated by the lab technician OUTSIDE the patient’s mouth.
Answer: Indirect restoration
500
A Die is a working replica of 2 or more teeth.
Answer: False
-A die is a working replica of Single Tooth. Typically removable from a cast.
500
To accelerate the setting time of gypsum material, you should:
A. Add borax
B. Add cold water
C. Add potassium sulfate
Answer: Add Potassium sulfate
-Borax-Retards (slow) the setting, longer to set
- Temperature of water applies to ALGINATE
- Potassium Sulfate- a common accelerator used for faster setting product.