Podcast
Questions and Answers
What is the primary advantage of dental stone over Plaster of Paris?
What is the primary advantage of dental stone over Plaster of Paris?
What is the purpose of using a mold in the casting process?
What is the purpose of using a mold in the casting process?
What is the ideal consistency of the dental stone mixture?
What is the ideal consistency of the dental stone mixture?
What is the recommended ratio of dental stone to water?
What is the recommended ratio of dental stone to water?
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What is the purpose of pouring the mixture behind the leading edge?
What is the purpose of pouring the mixture behind the leading edge?
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How long should the casting be left to harden before removing it from the ground?
How long should the casting be left to harden before removing it from the ground?
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What is the recommended time to wait before removing any soil or debris from the casting?
What is the recommended time to wait before removing any soil or debris from the casting?
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What is the purpose of labeling the casting with identifiers, date, location, and initials?
What is the purpose of labeling the casting with identifiers, date, location, and initials?
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What is the primary reason for using a ruler alongside the impression during photography?
What is the primary reason for using a ruler alongside the impression during photography?
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Why is casting more valuable than photography in certain cases?
Why is casting more valuable than photography in certain cases?
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What is a limitation of photography when enlarged to natural size?
What is a limitation of photography when enlarged to natural size?
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What was the casting material of choice prior to 1970?
What was the casting material of choice prior to 1970?
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Why is it important to position the camera directly 90° above the impression?
Why is it important to position the camera directly 90° above the impression?
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What is an advantage of casting over photography for deep impressions?
What is an advantage of casting over photography for deep impressions?
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What is the purpose of using Live View Mode or viewfinder during photography?
What is the purpose of using Live View Mode or viewfinder during photography?
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What is a disadvantage of using Plaster of Paris as a casting material?
What is a disadvantage of using Plaster of Paris as a casting material?
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What is the purpose of sifting a small amount of material over the impression to cover the bottom of the impression?
What is the purpose of sifting a small amount of material over the impression to cover the bottom of the impression?
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Which casting material is less flammable than sulfur?
Which casting material is less flammable than sulfur?
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What is the advantage of highlighting impressions in snow?
What is the advantage of highlighting impressions in snow?
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What is the recommended approach for working with moist snow?
What is the recommended approach for working with moist snow?
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What is the primary purpose of photographing impressions in snow?
What is the primary purpose of photographing impressions in snow?
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What is the characteristic of impressions in snow that varies considerably?
What is the characteristic of impressions in snow that varies considerably?
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Which casting material is known for producing excellent detail of snow impressions?
Which casting material is known for producing excellent detail of snow impressions?
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What is the recommended approach for casting larger impressions in snow?
What is the recommended approach for casting larger impressions in snow?
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Study Notes
Dental Stone vs. Plaster of Paris
- Dental stone is stronger and more durable than Plaster of Paris.
- Dental stone is easy to use and acquire.
- It is a form of plaster, made from calcium sulfate dehydrate, a natural material mined from the earth.
- Calcium sulfate dehydrate is calcinated (heated) to become calcium sulfate hemihydrate, the hardened version.
Using Dental Stone
- Dental stone is mixed with a pre-determined amount of water to achieve a consistency similar to thin pancake batter or thick cream.
- The mixture can be mixed in a container or a Ziplock bag.
- A metal form, cardboard, or built-up surrounding soil can be used as a mold to prevent the casting material from spreading.
- The mold should be slightly larger than the impression, and approximately 2lbs of dental stone to 8oz of water is used.
- The mixture is mixed for 3 minutes before pouring to ensure an even pour and a stronger cast.
The Pouring Process
- Start pouring the mixture just outside of the impression, directing the flow into the impression.
- Move along the impression while pouring to ensure the mixture fills the entire impression.
- Pour behind the leading edge to push the mixture into the impression.
- Once poured, the casting should be left to harden, and a label can be placed into the casting with identifiers, date, location, and initials.
Casting Footwear
- Casting footwear impressions is recommended whenever there is a 3-D impression.
- Casting captures the positive representation of the shoe, including uneven surfaces and microscopic characteristics.
- Casting provides tangible 3-dimensional evidence and confirms photographic evidence.
Casting Impressions in Snow
- Snow Print Wax, developed in 1982, is an aerosol spray that produces a wax shell when applied to the impression, allowing for casting with dental stone.
- Dry casting with dental stone involves layering the impression with dry dental stone and then preparing a regular mix of dental stone.
- Yellow Sulfur can be used to cast impressions in snow, but it is more time-consuming and requires melting and continuous stirring.
- Sulfur Cement, introduced in 2007, is less flammable than sulfur and requires the same method as sulfur.
Key Points
- The amount of detail varies considerably in different types and conditions of snow.
- Impressions in snow should always be photographed first.
- Highlighting impressions can enable better contrast recovered through photography.
- Casts of snow impressions provide additional detail to supplement photography of snow impressions alone.
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Description
Compare and contrast dental stone and plaster of Paris, including their properties, uses, and advantages. Learn about their applications in dentistry.
