1. Mr. Caputo Unit #1 Lesson #10
Diagnostic Cast
Mr. Caputo
Unit #1 Lesson #10

2. Today’s Class
Driving Question: How are diagnostic cast utilized in the dental office?
Learning Intentions: We will be able to describe various methods of constructing custom trays and demonstrate creating a light-cured custom tray.
Anchor: What personal protective equipment should be worn by the dental assistant when pouring a stone cast?

3. Diagnostic Cast Models
Duplicate patient’ s teeth and mouth structures for diagnostic purposes
Made from quality dental impressions
Used as models for further fabricating dental prostheses
Used as education tool
From initial casts dental prostheses are made that fit patient’s jaw structure and resemble other teeth

4. Gypsum Materials
Used in dentistry to create diagnostic cast models of maxillary or mandibular arch
Most common are plaster, stone, and high-strength stone
Composed primarily of calcium sulfate dihydrate
Supplied as powder
During setting process gypsum gives off heat in an exothermic reaction

5. Strengths of Gypsum Products
Plaster of Paris
Dental stone
Die stone
To learn more about gypsum products and
other dental materials, click here or go to
DentMat/default.asp

6. Plaster of Paris
Used for pouring cast models for preliminary study, diagnostic reasons, to attach casts onto articulators, and for general use in the dental lab when strength is not important
Because of porous and irregular particles, plaster requires more water when being mixed
Initial setting time is from 5 to 15 minutes and is completely set within 45 minutes
Removal of cast from mold too soon can result in fractures to the cast

7. Dental Model

8. Stone Available in yellow or buff color
Requires less water when mixing, and sets more slowly than plaster
When set, stone is harder, denser, and has a higher crushing strength than plaster
Harder stone casts provide excellent master casts for fabrication of dentures, bleach trays, athletic mouth guards, and temporary crown splints

9. Stone Spatulation is completed in 30 to 60 seconds on a vibrator
Initial setting time for artificial stone is usually 8 to 15 minutes and final setting time is approximately 45 minutes

10. Die Stone Strongest gypsum product
Used to create working casts for fixed prostheses and partial dentures
Most often poured by the dental laboratory technician
Mix must not be too thick or too thin so that it flows into the dentition easily and yet is thick enough to maintain strength

11. Preparing to Pour a Model

12. Steps to Pouring a Dental Model
Use a clean, dry mixing bowl and spatula
Measure volume of water and weigh powder
Always add powder to water and not water to powder
Spatulate thoroughly by hand, incorporating all the powder evenly throughout the mix until creamy
Avoid whipping the mix

13. Steps to Pouring a Dental Model
Vacuum mixing with a power mixer-investor helps eliminate incorporation of air into the mix
Hold bowl against a vibrator for a few minutes to cause trapped air to rise to the surface
Never add water to a mix that is too thick

14. Pouring of Models

15. Filling the Impression

16. Parts of a Cast Model Click here for a question to consider
Anatomic portion:
includes teeth and oral structures
the base
should make up two-thirds of the model
Art portion:
makes up one-third
Click here for a question to consider

17. Question to Consider
What is the difference between the maxillary and mandibular trimmed models?

18. Setting the Anatomic and Art Portions

19. Anatomic and Art Portion of a Dental Cast Model

20. Homework #4
Explain how you would train a dental worker in infection control.