Ceramic Crown Preparation Quiz & Flashcards

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Questions and Answers

What is the primary purpose of rounding all line and point angles in the preparation?

To improve the aesthetic appearance of the restoration

To make the preparation easier to clean

To increase the strength of the preparation

To avoid stress concentration and fracture (correct)

What is the recommended axial taper for all-ceramic crown preparations?

4-6 degrees

6-10 degrees (correct)

2-4 degrees

10-15 degrees

What is the primary purpose of the finish line in an all-ceramic crown preparation?

To improve the aesthetic appearance of the restoration

To provide a smooth, continuous margin for marginal integrity and periodontal health (correct)

To make the preparation easier to clean

To increase the retention of the crown

What is the recommended thickness for the finish line in an all-ceramic crown preparation?

1 mm Signup and view all the answers

What is the recommended amount of incisal reduction for an anterior all-ceramic crown preparation?

1.5-2 mm Signup and view all the answers

Which of the following diamond stones is NOT recommended for use in an anterior all-ceramic crown preparation?

Bur with sharp cutting edges Signup and view all the answers

What is the recommended degree of convergence for opposing proximal walls during restoration?

6-10 degrees Signup and view all the answers

Which type of stone is recommended for the reduction of the cingulum?

Tapered stone with a flat end Signup and view all the answers

What is the depth of reduction recommended for the palatal fossa?

1-1.5mm Signup and view all the answers

What is the primary purpose of preserving the curved horizontal surface between the lingual fossa and cingulum?

Retention Signup and view all the answers

Which feature is mandatory for ceramic restorations to avoid stress concentration?

Rounded preparation edges Signup and view all the answers

What instrument may be used to place the finish line subgingivally to improve aesthetics or retention of short abutments?

End cutting stone Signup and view all the answers

What is the primary reason for performing a two-plane reduction during labial reduction?

To minimize the risk of pulp exposure and preserve tooth structure Signup and view all the answers

What is the recommended depth of reduction for the labial surface during incisal preparation?

1.2 - 1.5 mm Signup and view all the answers

Which instrument is typically used for labial reduction during incisal preparation?

Flat-end tapered diamond stone Signup and view all the answers

What is the recommended finish line for labial reduction during incisal preparation?

90-degree rounded shoulder or deep chamfer Signup and view all the answers

In which direction should the depth grooves be made for the cervical one-third of the labial surface during two-plane reduction?

Parallel to the long axis of the tooth Signup and view all the answers

What is the recommended direction of cutting for the incisal two-thirds of the labial surface during two-plane reduction?

Following the contour of the labial surface Signup and view all the answers

Which of the following is NOT a disadvantage of all-ceramic crowns?

Excellent esthetic, translucency, and color stability Signup and view all the answers

Which of the following is a limitation for the use of all-ceramic crowns?

Young patient with large pulp size and high epithelial attachment Signup and view all the answers

Which of the following is NOT an indication for the use of all-ceramic crowns?

Fractured posterior teeth that cannot be restored with another more conservative restoration Signup and view all the answers

Which of the following is a disadvantage of all-ceramic crowns compared to metal-ceramic crowns?

Inability to perform radiographic examination to detect caries under the restoration Signup and view all the answers

What is the minimum occluso-gingival height requirement for all-ceramic crowns?

More than 1/3 of tooth height Signup and view all the answers

What is the main reason why all-ceramic crowns cannot be used on teeth with large pulp size and high epithelial attachment?

Extensive amount of tooth reduction required Signup and view all the answers

Study Notes

Preparation of All Ceramic Crowns

General guidelines:
- Smooth preparation and rounding of all line and point angles to avoid stress concentration and fracture
- Uniform sufficient reduction to give sufficient bulk for the ceramic for resistance and retention and structural durability

Axial Taper and Convergence

Axial taper: 6-10 degree occlusal convergence to give common path of insertion
Avoid over-convergence, which is inversely proportional to retention and resistance

Finish Line

Type: Deep chamfer or shoulder with round internal angle to avoid stress concentration
Thickness: 1mm
Location: Supra-gingival
Should be smooth and continuous for marginal integrity, structural durability, and periodontal preservation

Preparation of Anterior Teeth

Make putty index before preparation to check the amount of reduction and make provisional restorations
Diamond stones needed for proper preparations:
- Needle stone
- Tapered stone with round end for axial and incisal reductions
- Flame stone or football for palatal fossa
- Wheel stone for incisal reductions
- Finishing stones for rounding line and point angles of the preparation

Incisal Reduction

Amount of reduction: 1.5-2 mm, giving bulk for translucency of the incisal restoration
Direction: Incisal reduction is done with slight inclination 45° toward the lingo-gingival to oppose the forces perpendicularly on the incisal edge

Labial Reduction

Two sets of depth grooves are made cervically and incisally in a two-plane reduction using a tapered with flat end diamond stone instrument of known diameter
Depth of reduction: 1-1.5 mm (1.2 mm as an extra 0.3 mm will be added during the finishing process)
Finish Line: 90-degree rounded shoulder or deep chamfer 1-1.5 mm
Groove directions: Cervical 1/3 (parallel to the long axis of the tooth), incisal 2/3 (parallel to the contour of the labial surface)

Proximal Reduction

Direction: Opposing proximal walls should converge incisally 6-10 degrees
Instrument: Tapered stone with flat end
Depth of reduction: 1-1.5 mm

Palatal Reduction

A. Palatal Fossa:
- A sloping surface offers little resistance to tipping
- The curvature of the palatal fossa should be maintained, following the original concavity, while providing a 1mm clearance in all excursive movements
- Horizontal surface at the junction of the cingulum and fossa should be preserved
- Instrument: Wheel diamond stone or football stone
B. Cingulum:
- Reduced to have minimal convergence with the cervical portion of the labial surface
- Minimal taper is required to achieve maximum resistance, while mesio-distally the convexity is preserved
- Instrument: Tapered stone with flat end
- Depth of reduction: 1 mm

Finishing of the Preparation

All sharp line and point angles are rounded to avoid stress concentration
End-cutting stone may be used to safely place the finish line subgingivally to improve aesthetics or retention of short abutments

Advantages and Disadvantages of All Ceramic Crowns

Advantages:
- Excellent esthetics, translucency, and color stability
- Highly compatible with soft tissues, even if sub-gingival finish line, due to high smooth surface
- More conservative than metal ceramic
- Can be bonded to tooth structure → better retention & less marginal leakage
Disadvantages:
- High brittleness and liability to fracture
- More expensive than full metal & PFM
- Extensive amount of reduction compared to partial coverage, full metal
- Pulp vitality can't be done
- Radiographic examination can't be done to detect caries under the restoration

Indications and Limitations of All Ceramic Crowns

Indications:
- As a single restoration in cases with high esthetic demands
- As a retainer for all ceramic anterior bridge when esthetic is important
- In case of bad oral hygiene, root canal treated teeth, malposed teeth, and badly decayed teeth
- Fractured anterior teeth that cannot be restored with another more conservative restoration
- Proximal or facial caries that cannot be restored with another restoration
- Favorable occlusal forces
Limitations:
- Young patient with large pulp size & high epithelial attachment
- When more conservative treatment can be done
- Unfavorable occlusal loads

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Test your knowledge on the instruments, steps, and criteria for preparing all ceramic crowns in fixed prosthodontics. Learn about the advantages of using all ceramic crowns for excellent esthetics and compatibility with soft tissues.

All Ceramic Crown Preparation in Fixed Prosthodontics Lecture Quiz

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