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Questions and Answers
What is a key advantage of complete cast crowns over conservative restorations?
What is a key advantage of complete cast crowns over conservative restorations?
Which of the following describes a disadvantage of complete cast crowns?
Which of the following describes a disadvantage of complete cast crowns?
Why is it important to preserve tooth structure during crown preparation?
Why is it important to preserve tooth structure during crown preparation?
In which scenario would complete cast crowns be especially beneficial?
In which scenario would complete cast crowns be especially beneficial?
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What aspect of complete cast crowns allows them to support partial removable dental prostheses?
What aspect of complete cast crowns allows them to support partial removable dental prostheses?
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What must be considered while performing the reduction for a complete cast crown?
What must be considered while performing the reduction for a complete cast crown?
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What limitation can affect the use of complete cast crowns related to the smile line?
What limitation can affect the use of complete cast crowns related to the smile line?
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Which process is no longer feasible after the cementation of a complete cast crown?
Which process is no longer feasible after the cementation of a complete cast crown?
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Which teeth are primarily indicated for crown placement?
Which teeth are primarily indicated for crown placement?
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What is a contraindication for crown placement related to the treatment objectives?
What is a contraindication for crown placement related to the treatment objectives?
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What minimum clearance is required for functional cusps during crown preparation?
What minimum clearance is required for functional cusps during crown preparation?
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Which margin design is recommended for axial reduction?
Which margin design is recommended for axial reduction?
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What should be maintained during the reduction of a tooth for a crown?
What should be maintained during the reduction of a tooth for a crown?
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For nonfunctional cusp considerations, what minimum clearance is suggested at occlusoaxial line angles?
For nonfunctional cusp considerations, what minimum clearance is suggested at occlusoaxial line angles?
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What is the purpose of a functional cusp bevel?
What is the purpose of a functional cusp bevel?
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What feature can be added for additional retention in specific cases?
What feature can be added for additional retention in specific cases?
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What is the primary purpose of placing guiding grooves during tooth preparation?
What is the primary purpose of placing guiding grooves during tooth preparation?
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What depth should be verified for functional cusps during the clearance check?
What depth should be verified for functional cusps during the clearance check?
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What is the first step in the axial reduction technique?
What is the first step in the axial reduction technique?
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What should be done if overtapering of opposing axial walls is detected?
What should be done if overtapering of opposing axial walls is detected?
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During the finishing of the preparation, what should be done to finalize the chamfer margin?
During the finishing of the preparation, what should be done to finalize the chamfer margin?
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What should be used to measure the reduction depth during tooth preparation?
What should be used to measure the reduction depth during tooth preparation?
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What must be verified during the evaluation of preparation to ensure adequate clearance?
What must be verified during the evaluation of preparation to ensure adequate clearance?
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Which tool is typically used for initial reduction during tooth preparation?
Which tool is typically used for initial reduction during tooth preparation?
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What is a key consideration when performing interproximal care during axial reduction?
What is a key consideration when performing interproximal care during axial reduction?
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What is the purpose of adding retentive features during tooth preparation?
What is the purpose of adding retentive features during tooth preparation?
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Study Notes
Complete Cast Crown, Porcelain Fuse to Metal, and All Ceramic Preparation
- A complete cast crown is a durable restoration for badly damaged posterior teeth
- It covers all axial walls and the occlusal surface
- This restoration offers excellent longevity and can be used for single teeth or as retainers for fixed dental prostheses
Preparation Process
- Tooth Structure Removal: Adequate tooth structure must be removed to allow restoration to original contours
- Preservation: Tooth structure should be preserved when possible
- Strength Consideration: Reduction should produce a crown of acceptable strength
Advantages: Retention and Resistance
- Greater Retention: Complete cast crowns have superior retention compared to conservative restorations
- Improved Resistance: They offer better resistance form than partial-coverage restorations
- Strength: The cylinder-like configuration provides superior strength
Advantages: Contour Modification
- Axial Tooth Contour: Complete cast crowns allow modification of axial tooth contour
- Malaligned Teeth: Especially beneficial for malaligned teeth, within periodontal limits
- Furcation Access: Improved access to furcations through recontouring of buccal and lingual walls
Advantages: Special Requirements
- Partial Removable Dental Prostheses: Allows creation of properly shaped survey lines, guide planes, and occlusal rests
- Occlusion Modification: Permits easy modification of occlusion, important for supraerupted teeth
- Occlusal Plane: Helpful when reestablishing the occlusal plane is necessary
Disadvantages
- Extensive Tooth Structure Removal: Can have adverse effects on pulp and periodontium
- Gingival Inflammation: Proximity to gingiva may cause inflammation of gingival tissues
- Vitality Testing: Electric vitality testing is no longer feasible after cementation
Esthetic Considerations
- Patient Objection: Patients may object to the display of metal
- Smile Line: Normal smile line may restrict use to specific teeth
- Placement: May be limited to maxillary molars and mandibular molars and premolars
Indications
- Extensive coronal destruction: Maximum retention needed
- Short clinical crowns: High displacement forces anticipated
- Correction of axial contours: Support for partial removable dental prosthesis
Contraindications
- Conservative Options: Contraindicated if treatment objectives can be met with a more conservative restoration
- Intact Walls: Not recommended if intact buccal or lingual wall exists
- Esthetic Needs: Contraindicated for anterior teeth with high esthetic needs
Special Considerations
- Endodontically Treated Teeth: Complete cast crown is indicated on endodontically treated teeth for superior strength
- Additional Retentive Features: Grooves can be included for additional retention in specific cases
Cast Crown Preparation: Key Principles
Occlusal Reduction Guidelines
- Non-functional Cusps: Minimum 1 mm clearance required
- Functional Cusps: Minimum 1.5 mm clearance needed
- Anatomic Contours: Follow natural tooth shape for conservative preparation
Axial Reduction and Margin Design
- Axial Reduction: Parallel to tooth's long axis. 6° taper recommended
- Margin Configuration: Chamfer design. Ideally supragingival. 0.5 mm metal thickness
- Smoothness: Ensure distinct, smooth margins for optimal fit
Functional Cusp Bevel
- Placement: Directly beneath crown cusps for optimal contour
- Angle: Flatter than external surface, typically 45 degrees
- Purpose: Ensures durability and conserves tooth structure
Nonfunctional Cusp Considerations
- Clearance: Minimum 0.6 mm at occlusoaxial line angles
- Additional Bevel: Often needed for maxillary molars
- Mandibular Molars: May not require additional reduction due to inclination
Key Takeaways for Crown Preparation
- Precise Measurements: Follow recommended clearances for each area
- Anatomic Contours: Maintain natural tooth shape during reduction
- Margin Quality: Ensure smooth, distinct chamfer margins
- Proper Bevels: Angle functional and nonfunctional cusps correctly
Step By Step Procedure For Preparing a Tooth (Image-Based)
- This section describes a step-by-step visual guide to tooth preparation.
Guiding Grooves for Occlusal Reduction
- Central Groove: Place 1 mm deep holes in fossae, connect along central groove
- Developmental Grooves: Place guiding grooves in buccal and lingual developmental grooves
- Functional Cusp Bevel: Place 1.5 mm deep groove for centric stop, diminishing cervically
Occlusal Reduction Technique
- Place Guiding Grooves: Ensure accurate position, depth, and angulation of grooves
- Remove Tooth Structure: Use carbide or diamond to remove structure between grooves
- Check Clearance: Verify 1.5 mm clearance on functional cusps, 1.0mm on nonfunctional
Alignment Grooves for Axial Reduction
- Placement: Three grooves on buccal and lingual walls
- Instrument Angle: Diamond bur parallel to restoration path of placement
- Depth Control: Tip buried to midpoint to avoid unsupported enamel
- Path of Placement: Grooves determine restoration's path of placement
Axial Reduction Technique
- Remove Islands: Remove tooth structure between alignment grooves
- Interproximal Care: Prevent damage to adjacent teeth during reduction
- Chamfer Placement: Place 0.5 mm wide cervical chamfer during axial reduction
Finishing the Preparation
- Smooth Transitions: Create smooth transitions from occlusal to axial surfaces
- Margin Refinement: Use fine-grit diamond for smooth chamfer margin
- Surface Finishing: Round line angles and place nonfunctional cusp bevel
- Additional Features: Add retentive features like grooves or boxes if needed
Evaluation of Preparation
- Taper Assessment: Check for overtapering of opposing axial walls
- Undercut Check: Ensure no undercuts between opposing axial walls
- Clearance Verification: Assess occlusal and proximal clearances for adequacy
Common Errors and Corrections
- Error: Overtapering
- Correction: Upright walls or add retentive features
- Error: Undercuts
- Correction: Eliminate with diamond instrument
- Error: Inadequate clearance
- Correction: Adjust before making interim restoration
Tools and Instruments
- Diamond Burs: For initial reduction and finishing
- Carbide Burs: For occlusal reduction and retentive features
- Periodontal Probe: For measuring reduction depth
- Wax Caliper: For checking occlusal clearance
Final Steps
- Interim Restoration: Create temporary crown after preparation is complete
- Impression Making: Take final impression for fabrication of permanent crown
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Description
This quiz covers the preparation techniques for complete cast crowns, porcelain fused to metal, and all-ceramic restorations. Learn about tooth structure removal, retention and resistance advantages, and the importance of contour modification. Test your knowledge on creating durable restorations for posterior teeth.
