Questions and Answers
What is the primary purpose of an opposing cast?
A working cast is a positive representation of the prepared teeth only.
False
What is a single die?
A positive replica of a single prepared tooth obtained from a single copper band impression.
The ideal requirements of a die include being free from _____ or defects, especially at the finish line.
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Which material is NOT listed as a classification for single die?
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A flexible die is made from heavy body silicone impression material.
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What is one advantage of using an electroplated die?
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The _____ cast keeps the relationship between the abutment fixed and immovable.
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Match the following types of dies with their characteristics:
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What is a disadvantage of using a resin die?
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Which technique does NOT rely on dowel pins?
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The Pindex system involves drilling holes in the working cast after the impression has fully set.
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What is the purpose of die relief (die spacer) in die preparation?
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The ___________ technique uses a 2 cm tapered brass or stainless steel post to prevent die rotation.
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Match the CAD/CAM systems with their descriptions:
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What is one major disadvantage of CAD/CAM systems?
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Die hardening increases the durability of the die against abrasion during carving.
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What should be avoided when drawing the finish line on the die?
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The ___________ technique involves using a saw frame to improve die separation from the cast.
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What is a risk associated with using removable dies?
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Study Notes
Working Cast & Die Overview
- Working cast is the positive replica of prepared teeth and dental arch structures.
- Opposing cast represents non-prepared teeth and other parts of the opposing arch.
- Single die is a positive replica of a single prepared tooth from a copper band impression.
- Removable die can be taken out for adjustments while ensuring proper proximal relationships.
Requirements of Ideal Cast
- Accurately reproduces both prepared and unprepared teeth.
- Captures edentulous areas.
- Free from distortions or voids.
- Properly trimmed to allow access for carving wax pattern margins.
Importance of Recording Unprepared Teeth
- Ensures proper occlusion.
- Maintains proximal contact.
- Preserves contour and anatomical accuracy based on contralateral teeth.
Requirements of Ideal Die
- Accurately reproduces only the prepared tooth.
- Must be free from bubbles or defects, particularly at the finish line.
- Accurately represents the finish line.
Ideal Die Material Characteristics
- High strength to withstand handling without fracture.
- High hardness to resist scratches and abrasion.
- Excellent dimensional accuracy and stability.
- Good color contrast for detecting preparation margins.
- Compatibility with impression materials.
- High wettability with wax for optimal flow.
Classifications of Casts and Dies
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Construction Techniques:
- Single die.
- Working cast with removable die.
- Working cast with separate die.
- Virtual cast and die.
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Single Die Materials:
- Dental stone die (Type IV or V).
- Resin or epoxy die.
- Electroplated die (e.g., silver or copper plated).
- Flexible die.
Single Die Materials
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Stone Die (Type IV/V):
- High mechanical properties.
- Adequate dimensional stability.
- Cost-effective and easy to fabricate.
- Low abrasion resistance and brittle.
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Resin Die:
- High strength and abrasion resistance.
- Incompatibility with certain materials like hydrocolloids.
- Expensive and time-consuming.
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Electroplated Die:
- Layered metal deposition on impression surface.
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Flexible Die:
- Made from silicone material for easy removal of the restoration.
- Fast setting and good detail reproduction.
Working Cast with Separate Die
- Uses double pour technique; first pour is more accurate.
- Maintains the abutment's fixed relationship.
- Advantage: Simplicity and stability.
- Disadvantages: Potential distortion during transfer and lower accuracy in second pour.
Working Cast with Removable Die
- Allows easy access for adjustments while preserving the relationship with adjacent teeth.
- Requires stability and precision to avoid movement.
- Techniques include Dowel pin, Pindex system, Di-Lock tray.
Dowel Pin Technique
- Utilizes tapered pins for interlocking with stone.
- Involves precise positioning before the first pour of working cast.
- Requires careful cutting and separation to avoid locking.
Pindex System
- Employs a base, light indicator, and drill to position pins accurately.
- After setting, pins are cemented in place.
Die Preparation Steps
- Die Trimming: Remove parts mesial and distal to prepared tooth; taper handle for easy handling.
- Ditching: Create a circumferential groove below the finish line for better accessibility.
- Drawing the Finish Line: Lighten the finish line with a red pencil for visibility, avoiding carbon contamination.
- Die Relief (Spacer): Provides a space for cement, leaving a band uncoated to ensure proper fit.
- Die Hardening: Apply agents like cyano-acrylate to resist abrasion.
Virtual Cast & Die
- Involves scanning, designing, and manufacturing using CAI/CAD/CAM technologies.
- Scanning can be intra-oral or extra-oral for various structures including impressions and articulators.
- CAD software is used for precise design and planning of restorations.
CAI/CAD/CAM Systems
- Direct Chair-side System: Same-day restorations.
- Indirect Lab-side System: Traditional physical impressions sent to the lab.
- Integrated System: Data sent online for lab designs and milling.
Advantages and Disadvantages of CAD/CAM
- Advantages: New material introduction (zirconia), efficient, no physical impressions, improved documentation.
- Disadvantages: High costs, required training, material waste from milling.
Uses of CAD/CAM Systems
- Construction of fixed and removable restorations and orthodontic appliances.
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Description
This quiz covers the fundamental concepts of working casts, opposing casts, and single dies used in dentistry. It will help you understand the distinctions between different types of dental replicas and their applications in dental practice. Ideal for students and professionals looking to reinforce their knowledge in dental materials.
