Porcelain and Cast Crown Preparation

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Questions and Answers

What is the primary purpose of a complete cast crown?

To enhance the aesthetic appearance of teeth

To provide a durable restoration for badly damaged posterior teeth (correct)

To serve as a temporary solution for tooth decay

To enable easy removal and reapplication

Which of the following is NOT an advantage of complete cast crowns?

Enhanced aesthetic appeal for anterior teeth (correct)

Improved resistance against forces

Strength due to the cylinder-like configuration

Greater retention compared to conservative restorations

What is a significant preparation requirement when creating a complete cast crown?

Reducing less tooth structure than necessary

Minimizing the occlusal surface area

Preserving as much tooth structure as possible (correct)

Allowing for complete removal of the tooth pulp

What is one disadvantage of using complete cast crowns?

They require extensive tooth structure removal Signup and view all the answers

How do complete cast crowns assist in occlusion modification?

By enabling easy changes to the occlusion for supraerupted teeth Signup and view all the answers

Which condition can arise due to the proximity of a complete cast crown to gingival tissue?

Gingival inflammation Signup and view all the answers

What modification capability do complete cast crowns offer for malaligned teeth?

They facilitate contour modification within periodontal limits Signup and view all the answers

What happens to the feasibility of electric vitality testing after cementation of a complete cast crown?

It is no longer feasible Signup and view all the answers

For which teeth is placement of a cast crown particularly limited?

Maxillary molars and mandibular molars and premolars Signup and view all the answers

What is one of the contraindications for placing a cast crown on anterior teeth?

High esthetic needs Signup and view all the answers

What is the minimum clearance required for non-functional cusps during occlusal reduction?

1 mm Signup and view all the answers

Which type of crown is indicated for endodontically treated teeth?

Complete cast crown Signup and view all the answers

What angle should the functional cusp bevel be compared to the external surface?

Typically 45 degrees Signup and view all the answers

Which aspect is NOT a key takeaway for crown preparation?

Utilize a parallel margin configuration Signup and view all the answers

What type of margin configuration is recommended for a chamfer design?

Supragingival with 0.5 mm thickness Signup and view all the answers

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

0.6 mm Signup and view all the answers

What is the purpose of placing guiding grooves during occlusal reduction?

To ensure accurate positioning and depth of grooves Signup and view all the answers

Which depth is specified for the functional cusp bevel during preparation?

1.5mm Signup and view all the answers

What should be assessed for adequacy during evaluation of preparation?

Occlusal and proximal clearances Signup and view all the answers

Which error is corrected by implementing upright walls or adding retentive features?

Overtapering Signup and view all the answers

What is the purpose of chamfer placement during axial reduction?

To provide a smooth transition between surfaces Signup and view all the answers

To prevent damage during axial reduction, what should be done regarding interproximal care?

Avoid contact with adjacent teeth Signup and view all the answers

What is the ideal action to eliminate undercuts during preparation?

Utilize a diamond instrument Signup and view all the answers

Which instrument is primarily used for measuring reduction depth?

Periodontal probe Signup and view all the answers

What type of restoration is created after the tooth preparation is completed?

Temporary crown Signup and view all the answers

What feature should be added if needed during surface finishing?

Grooves or boxes 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.
It 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 the restoration to conform to the original contours.
Preservation: Tooth structure should be preserved whenever possible.
Strength Consideration: Reduction of tooth structure 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 of complete crowns 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 re-establishing the occlusal plane is necessary.

Disadvantages

Extensive Tooth Structure Removal: Can cause 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 on specific teeth.
Placement: May be limited to maxillary molars and mandibular molars and premolars.

Indications

Extensive Coronal Destruction: Maximum retention is needed.
Short Clinical Crowns: High displacement forces are anticipated.
Correction of Axial Contours: Support for partial removable dental prostheses is needed.

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 aesthetic needs.

Special Considerations

Endodontically Treated Teeth: Complete cast crowns are 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 the 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

(This section is a procedure, not specific details.)

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 mm 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 the permanent crown.

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Description

This quiz covers the preparation process for complete cast crowns, including tooth structure removal and the importance of preservation. You'll learn about the advantages of complete cast crowns, focusing on retention and resistance. Enhance your understanding of dental restorations with this informative quiz.