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Questions and Answers
What is the primary reason why impression waxes are rarely used to record complete impressions?
What is the primary reason why impression waxes are rarely used to record complete impressions?
What is the characteristic of impression waxes that allows them to be moldable at a temperature tolerated by oral tissues?
What is the characteristic of impression waxes that allows them to be moldable at a temperature tolerated by oral tissues?
What is the ratio of low melting paraffin and bees waxes in impression waxes?
What is the ratio of low melting paraffin and bees waxes in impression waxes?
What is the primary advantage of using impression waxes in dentistry?
What is the primary advantage of using impression waxes in dentistry?
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What is the property of impression waxes that allows them to be used for extending tray borders or adapting a stock tray?
What is the property of impression waxes that allows them to be used for extending tray borders or adapting a stock tray?
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What is the type of impression material that impression waxes are classified as?
What is the type of impression material that impression waxes are classified as?
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What is the primary use of impression compound in dentistry?
What is the primary use of impression compound in dentistry?
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What are the thermal properties of impression compound?
What are the thermal properties of impression compound?
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Which of the following is NOT a component of impression compound?
Which of the following is NOT a component of impression compound?
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What is the primary function of stearic acid, shellac, and gutta-percha in impression compound?
What is the primary function of stearic acid, shellac, and gutta-percha in impression compound?
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What is a characteristic of muco-compressive materials?
What is a characteristic of muco-compressive materials?
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What is the purpose of corrective impression wax?
What is the purpose of corrective impression wax?
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What has replaced waxes for bite registration?
What has replaced waxes for bite registration?
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What is an advantage of the impression compound?
What is an advantage of the impression compound?
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Why is a water bath preferred when softening the impression compound?
Why is a water bath preferred when softening the impression compound?
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What should be done with the impression once it has been taken?
What should be done with the impression once it has been taken?
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What is not a characteristic of the impression compound?
What is not a characteristic of the impression compound?
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What is a disadvantage of the impression compound?
What is a disadvantage of the impression compound?
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Study Notes
Impression Materials
Impression Waxes
- Considered one of the first impression materials in dentistry.
- Characteristics: cheap, clean, user-friendly.
- Available in various consistencies: soft, medium, hard, and extra hard.
- Described as rigid, muco-static, hydrophobic, and reversible; softens with heat and hardens upon cooling (thermoplastic).
- Composed of low melting paraffin and beeswax in a 3:1 ratio.
- High coefficient of thermal expansion leads to distortion when removed from undercuts.
- Not commonly used for complete impressions due to weak mechanical properties.
- Solid at mouth temperature but moldable when heated to tolerable levels for oral tissues.
- Formats include sticks, strips, and tubes.
- Key types include:
- Corrective Impression Wax: Used to register soft tissue details over original impressions.
- Bite-Registration Wax: For accurately articulating opposing arches, now often replaced by silicone and polyether materials.
Impression Compound
- One of the oldest dental impression materials.
- Classified as inelastic (rigid), hydrophobic, mucocompressive, and reversible thermoplastic.
- Primarily employed for making primary impressions of edentulous mouths.
- Alternative names include dental compound, model compound, and model plastic.
- Presentation: available as cakes, sticks, and cones.
- Setting reaction involves no chemical change; softens with heat and hardens upon cooling.
Composition
- General composition includes:
- Natural or synthetic resin for cohesion and flowance.
- Waxes (40%): provides thermoplasticity and flow.
- Stearic acid, shellac, gutta-percha (3%): assists in consistency.
- Diatomaceous earth, French chalk, or talc (50%): contributes to thermoplasticity.
- Utilizes low thermal conductivity; requires thorough heating, ideally in a water bath.
- Can be reused for the same patient if errors occur; inaccurate portions can be remade without duplicating the entire impression.
Advantages of Impression Compound
- Compatible with model materials; does not require a separating medium before pouring plaster.
- Reusable and adaptable, allowing for corrections.
- No need for a special tray.
- Effective for techniques needing a tight peripheral seal.
- Can be combined with other materials.
- Cost-effective.
Drawbacks of Impression Compound
- Rigid once set, leading to distortion; not suitable for undercut areas.
- Acts as a muco-compressive material, potentially displacing soft tissue.
- Fails to reproduce fine surface detail owing to high viscosity and low flow.
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Description
Test your knowledge on different types of impression waxes and materials used in dentistry. Learn about corrective impression wax, bite-registration wax, and impression compound.
