Dental Materials: Complete Cast Crown Preparation

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Questions and Answers

Which scenario would indicate the use of a complete cast crown?

In cases with extensive coronal destruction (correct)

For anterior teeth with high esthetic needs

When the tooth has intact buccal and lingual walls

When treatment can be managed with a conservative restoration

What is the minimum required occlusal clearance for functional cusps?

1 mm

2 mm

0.5 mm

1.5 mm (correct)

Which design feature is preferred for margin configuration in crown preparation?

Shoulder design

Bevel design

Chamfer design (correct)

Conical design

What is the primary purpose of removing tooth structure during the preparation of a complete cast crown?

To ensure better retention and resistance Signup and view all the answers

In what condition is a cast crown contraindicated for anterior teeth?

If esthetic needs are high Signup and view all the answers

Which feature of complete cast crowns enhances their strength?

Cylinder-like configuration Signup and view all the answers

What additional feature can be included in cast crown design for enhanced retention?

Grooves Signup and view all the answers

What should be maintained during reduction to preserve the integrity of the crown preparation?

Natural tooth shape Signup and view all the answers

Why might complete cast crowns be beneficial for malaligned teeth?

They allow for contour modification Signup and view all the answers

What is a potential disadvantage of using complete cast crowns?

Gingival inflammation Signup and view all the answers

What is the minimum clearance needed at occlusoaxial line angles for nonfunctional cusp considerations?

0.6 mm Signup and view all the answers

What is the recommended angle configuration for functional cusp bevel placement?

45 degrees Signup and view all the answers

What aspect of complete cast crowns assists in the proper fitting of partial removable dental prostheses?

Survey lines and guide planes Signup and view all the answers

What is a major concern related to electric vitality testing after cementation of complete cast crowns?

It is no longer feasible Signup and view all the answers

In what way do complete cast crowns allow for occlusion modification?

By easily modifying the occlusal surface Signup and view all the answers

What esthetic consideration may limit the use of complete cast crowns?

Their visibility in the smile line Signup and view all the answers

What is the depth for the groove placed on functional cusps during occlusal reduction?

1.5 mm Signup and view all the answers

Which instrument is primarily used for occlusal reduction?

Carbide Burs Signup and view all the answers

What should be done to check for insufficient clearance after tooth preparation?

Assess occlusal and proximal clearances Signup and view all the answers

What is a common correction for overtapering during tooth preparation?

Add retentive features Signup and view all the answers

How deep should guiding grooves be when preparing a tooth?

1 mm for central groove Signup and view all the answers

What is the purpose of alignment grooves in axial reduction?

To guide the restoration's path of placement Signup and view all the answers

What can be used to measure reduction depth during tooth preparation?

Periodontal Probe Signup and view all the answers

What is the purpose of creating smooth transitions from occlusal to axial surfaces?

To minimize stress concentration Signup and view all the answers

What specific width is recommended for the cervical chamfer placed during axial reduction?

0.5 mm Signup and view all the answers

What is the first step in the finishing preparation process?

Smoothing Transitions Signup and view all the answers

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 is known for its 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 the restoration to return to its original contours.
Preservation: Tooth structure should be preserved whenever possible.
Strength Consideration: The reduction should produce a crown with 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.
High Displacement Forces Anticipated: Maximum retention needed.
Short Clinical Crowns: High displacement forces anticipated.
Correction of Axial Contours: Support for partial removable dental prostheses.

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.

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 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

(Images required for this section are not described in the document.)

Guiding Grooves for Occlusal Reduction

Central Groove: Place 1mm deep holes in fossae, connect along central groove.
Developmental Grooves: Place guiding grooves in buccal and lingual developmental grooves.
Functional Cusp Bevel: Place 1.5mm 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 1.5mm clearance on functional cusps, 1.0mm on nonfunctional.

Alignment Grooves for Axial Reduction

Placement: Three grooves on buccal and lingual walls.
Instrument Angle: Diamond bure 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 0.5mm 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 process for complete cast crowns, detailing their advantages in dental restoration. Explore the necessary steps for tooth structure removal, preservation techniques, and the benefits of this durable option for posterior teeth. Perfect for dental students and professionals looking to enhance their knowledge.