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All Ceramic Crown Preparation in Fixed Prosthodontics Quiz
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All Ceramic Crown Preparation in Fixed Prosthodontics Quiz

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Questions and Answers

Why is it important to have a deep chamfer or shoulder finish line in crown preparations?

  • To avoid stress concentration (correct)
  • To increase stress concentration
  • To reduce marginal integrity
  • To decrease structural durability
  • What is the recommended range for axial taper in the preparation of all ceramic crowns?

  • 6-10 degrees (correct)
  • 10-15 degrees
  • 3-5 degrees
  • 5-8 degrees
  • What is the purpose of using a putty index before tooth preparation?

  • To skip provisional restorations
  • To increase the amount of reduction
  • To check the amount of reduction (correct)
  • To speed up the process
  • Which type of diamond stone is recommended for incisal reductions in tooth preparation?

    <p>Tapered stone with round end</p> Signup and view all the answers

    What is the range for the amount of incisal reduction needed in crown preparations?

    <p>1.5-2 mm</p> Signup and view all the answers

    Why is it necessary to round line and point angles during crown preparation?

    <p>For structural durability</p> Signup and view all the answers

    Why is incisal reduction done with a slight inclination toward the lingo-gingival?

    <p>To preserve the retention &amp; resistance features of the preparation</p> Signup and view all the answers

    What is the depth of reduction recommended for labial reduction?

    <p>1-1.5mm</p> Signup and view all the answers

    What is the purpose of making grooves in labial reduction?

    <p>To remove tooth structure between the grooves</p> Signup and view all the answers

    Why are depth grooves made before creating a straight plane for the incisal edge?

    <p>To guide the depth of preparation</p> Signup and view all the answers

    What is the precise direction for cutting during labial reduction for 2 plane reduction?

    <p>Starting with the incisal 2/3 after removal of maximum convexity, then gingival 1/3</p> Signup and view all the answers

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

    <p>To enhance tooth durability</p> Signup and view all the answers

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

    <p>1.5 mm</p> Signup and view all the answers

    What is the ideal convergence angle for the proximal walls in a restoration preparation?

    <p>6-10 degrees</p> Signup and view all the answers

    What feature of the preparation is responsible for providing resistance and retention to the final restoration?

    <p>The curved horizontal surface between the lingual fossa and cingulum</p> Signup and view all the answers

    Which instrument is recommended for reducing the palatal fossa area?

    <p>Any of the above</p> Signup and view all the answers

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

    <p>Both a and b</p> Signup and view all the answers

    Which feature of the preparation acts as an anti-rotation feature?

    <p>The curved horizontal surface between the lingual fossa and cingulum</p> Signup and view all the answers

    Which of the following is NOT an advantage of all-ceramic crowns?

    <p>More conservative than metal-ceramic crowns</p> Signup and view all the answers

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

    <p>Poor esthetic properties and color instability</p> Signup and view all the answers

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

    <p>As a restoration for teeth with large pulp size and high epithelial attachment</p> Signup and view all the answers

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

    <p>Patient with heavy bite, deep bite, or edge-to-edge occlusion</p> Signup and view all the answers

    Which of the following statements is TRUE regarding the preparation of all-ceramic crowns?

    <p>The preparation should be extensive, as all-ceramic crowns require more tooth reduction compared to partial coverage restorations.</p> Signup and view all the answers

    Which of the following statements is FALSE regarding the limitations of all-ceramic crowns?

    <p>All-ceramic crowns are not recommended for teeth with excessive short clinical crowns more than 1/3 of the occluso-gingival height.</p> Signup and view all the answers

    Study Notes

    Incisal Reduction

    • Incisal reduction is done with a slight inclination of 45° towards the lingo-gingival to oppose the forces perpendicularly on the incisal edge.
    • Start by making 1.8 mm depth grooves and connect them to make the incisal edge into one straight plane.

    Labial Reduction

    • Two sets of depth grooves are made cervically and incisally using a tapered flat-end diamond stone instrument.
    • Tooth structure in between the grooves is removed.
    • Instrument: flat-end tapered diamond stone.
    • Depth of reduction: 1-1.5 mm (1.2 mm with an extra 0.3 mm added during the finishing process).
    • Finish line: 90-degree rounded shoulder or deep chamfer 1-1.5 mm.
    • Grooves directions: Cervical 1/3 (parallel to the long axis of the tooth) and incisal 2/3 (parallel to the contour of the labial surface).
    • Labial reduction direction: start with the gingival 1/3 parallel to the long axis of the tooth, then adjust to follow the direction of the incisal 2/3.

    Purpose of Two-Plane Reduction

    • To follow the anatomy of the surface (conservative reduction, preserving retention and resistance features).
    • To avoid pulp encroachment.
    • To allow enough space for a uniform porcelain layer, displaying proper esthetics and avoiding an overcontoured restoration.

    General Guidelines for Preparation of All Ceramic Crowns

    • Axial taper: 6-10 degree occlusal convergence to give a common path of insertion.
    • Finish line: deep chamfer or shoulder with a round internal angle to avoid stress concentration.
    • Thickness: 1 mm.
    • Location: supra-gingival.
    • Should be smooth and continuous for marginal integrity, structural durability, and periodontal preservation.

    Preparation of Anterior Teeth

    • Make a putty index before preparation to check the amount of reduction and make provisional restorations.
    • Diamond stones needed:
      • 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

    • Amount of incisal reduction: 1.5-2 mm, giving bulk for translucency of the incisal restoration.

    Advantages and Disadvantages of All Ceramic Crowns

    • Advantages:
      • Excellent esthetic, translucency, and color stability
      • Highly compatible with soft tissues
      • More conservative than metal ceramic
      • Can be bonded to tooth structure
    • Disadvantages:
      • High brittleness and liability to fracture
      • More expensive than full metal and PFM
      • Extensive amount of reduction compared to partial coverage and full metal
      • Pulp vitality cannot be done
      • Radiographic examination cannot be done to detect caries under the restoration

    Indications and Limitations of All Ceramic Crowns

    • Indications:
      • Single restoration in cases with high esthetic demands
      • As a retainer for all ceramic anterior bridge
      • 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 and high epithelial attachment
      • When more conservative treatment can be done
      • Unfavorable occlusal loads
      • Excessive short teeth more than 1/3 occluso-gingival height

    Proximal Reduction

    • Direction: opposing proximal walls should converge incisally 6-10 degree.
    • Instrument: tapered stone with flat end.
    • Depth of reduction: 1-1.5 mm.

    Palatal Reduction

    • Palatal fossa:
      • A sloping surface offers little resistance to tipping.
      • The curvature of the palatal fossa should be maintained following the original concavity.
      • Instrument: wheel diamond stone or football stone.
    • Cingulum:
      • Reduced to have minimal convergence with the cervical portion of the labial surface.
      • 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.

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    Description

    Test your knowledge on all ceramic crown preparation in fixed prosthodontics from the lecture by Dr. Alaa El-Ashkar. Learn about the instruments, steps, and criteria for all ceramic crown preparation, as well as the advantages of this method.

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