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Questions and Answers
Which material is used to create a positive replica of the prepared tooth in dental procedures?
Which material is used to create a positive replica of the prepared tooth in dental procedures?
- Cements for temporary crowns
- Electroplated metals
- Type II dental plaster (correct)
- Polymers for orthodontics
What is the most significant factor affecting the physical properties of gypsum used in dental applications?
What is the most significant factor affecting the physical properties of gypsum used in dental applications?
- Particle color consistency
- Water/powder ratio (correct)
- Humidity during storage
- Size of the sample container
In terms of particle size and shape, which property is most beneficial for dental gypsum?
In terms of particle size and shape, which property is most beneficial for dental gypsum?
- Fine and uniform particles (correct)
- Coarse irregular particles
- Heterogeneous particle distribution
- Spherical particle shape
Which of the following accurately describes a common application of electroformed metals in dentistry?
Which of the following accurately describes a common application of electroformed metals in dentistry?
What is a primary characteristic of Type II dental plaster that makes it suitable for dental applications?
What is a primary characteristic of Type II dental plaster that makes it suitable for dental applications?
What is a primary function of impression materials in dentistry?
What is a primary function of impression materials in dentistry?
Which aspect of gypsum affects its physical properties in dental applications?
Which aspect of gypsum affects its physical properties in dental applications?
What is the importance of the water/powder ratio when preparing gypsum for dental use?
What is the importance of the water/powder ratio when preparing gypsum for dental use?
In constructing casts and dies, what property of gypsum is most critical?
In constructing casts and dies, what property of gypsum is most critical?
What role does silica play when mixed with gypsum for investment purposes?
What role does silica play when mixed with gypsum for investment purposes?
What is a primary use of Type II dental plaster?
What is a primary use of Type II dental plaster?
In the flasking procedure for acrylic dentures, which material is crucial for the process?
In the flasking procedure for acrylic dentures, which material is crucial for the process?
Which of the following describes a significant application of model plaster in dentistry?
Which of the following describes a significant application of model plaster in dentistry?
Which characteristic makes Type II gypsum suitable for dental applications?
Which characteristic makes Type II gypsum suitable for dental applications?
What is the significance of the articulation of stone casts in dentistry?
What is the significance of the articulation of stone casts in dentistry?
What is the W/P ratio for Type IV dental stone?
What is the W/P ratio for Type IV dental stone?
How does the strength of Type IV stone compare to Type III stone?
How does the strength of Type IV stone compare to Type III stone?
Which statement accurately defines Type IV dental stone?
Which statement accurately defines Type IV dental stone?
What is the implication of a lower W/P ratio when using dental stone materials?
What is the implication of a lower W/P ratio when using dental stone materials?
Which of the following factors primarily affects the strength of dental gypsum materials?
Which of the following factors primarily affects the strength of dental gypsum materials?
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Study Notes
Dental Applications of Gypsum
- Gypsum is used in dental applications for impression materials, constructing casts and dies, an making investment materials when mixed with silica fillers.
- Die: A positive replica of a prepared tooth used to fabricate inlays and crowns.
- Type II Dental Plaster: Used to make diagnostic casts, articulate stone casts, and for flasking procedures for acrylic dentures (cast end).
- Model Plaster (Type II): Also used for flasking procedures for acrylic dentures (teeth end).
- Dental Stone (Type III): Used for master casts in the fabrication of wax patterns for cast restorations, such as crowns and bridges. Stronger than plaster and requires less water (W/P ratio of 0.35, 35 ml water to 100 g powder).
- Dental Stone (Hydrocal): Used for flasking procedures for acrylic dentures (teeth end).
Materials for Dental Applications
- Metals: Electroformed and electroplated
- Polymers: Used in a variety of dental applications
- Cements: Used for bonding and restoration
- Ceramics: Used for aesthetic restorations
Dental Stone Type IV
- Used for making diagnostic casts, articulation of stone casts, and flasking acrylic dentures
- W/P ratio of 0.22 (22ml water to 100g powder)
- Almost twice as strong as type III stone
- Solubility: hemihydrate dissolves in water forming Ca &SO4 ions, which react with water to form CaSO4 dihydrate
- Setting Expansion is double that of Type III
- Working Time: Approximately 3 minutes
- Initial setting time: Approximately 12 minutes, indicated by loss of gloss
- Final setting time: Time elapsed from mixing until the reaction is complete
- Disadvantages: Does not reproduce fine details as well as dental stone due to high viscosity of epoxy resin paste, shrinks by about 0.1% during hardening, and is expensive.
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