Enhanced Verifiable CPD from the
University of Birmingham

ORE Masterclass
Metal-Ceramic (PFM) Crown Preparation Upper Incisor

Preparing a tooth for a porcelain-fused-to-metal (Metal-Ceramic) crown is one of the practical tests used in ORE Part 2.

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    Welcome to this Masterclass Slide Show.
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    This slide show will take you through the steps needed to prepare for a Porcelain-Fused-to-Metal (PFM) crown in a typodont maxillary incisor.
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    A silicone index will be used to assess the preparation depths.
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    If you prepare too close to the gingival margin, your final prep will be too thin, as Frascati typodont teeth get very narrow near the neck.
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    Remember the buccal face has two planes, so a single full height cut will not work.
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    Now the second cut. Remember the buccal face has two planes, so a single full height cut will not work.
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    A PFM requires a minimum of 1.2mm of space for an acceptable appearance.
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    Use a needle bur initially when working interproximally.
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    Do not use the torpedo until the needle bur has done most of the work.
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    Incisal edge reduction should be 2mm.
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    The palatal is covered in metal only, so only 0.5mm of space is needed.
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    Note the buccal margin is 90°. The other margins are bevelled.
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    Convergence should ideally be 5 degrees each side.
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ORE Instructions

METAL CERAMIC CROWN PREPARATION. Prepare the tooth indicated to receive a metal ceramic crown. The tooth should be prepared for:

  • a metal margin all round the tooth;
  • for a molar tooth for the porcelain to cover the buccal surface, and extend over the buccal cusp to just short of the central fossa;
  • for an anterior tooth for the porcelain to cover the labial, incisal, and proximal surfaces of the tooth up to contact points.

The laboratory instructions may also need to be completed.

ORE Desirable Features

1. Index Preparation

  • Sectioned once in the middle of the tooth

2. Occlusal Reduction

  • 2.0 mm over occlusal surface / incisally for metal and porcelain
  • Otherwise 0.75 - 1 mm

3. Axial Reduction

  • Sufficient to give 6° - 20° taper
  • 1.2 mm labially and 0.5 - 1.0 mm lingually

4. Margin

  • Continuous around the tooth
  • 0.5 - 0.75 mm chamfer palatally and extending to just buccal to the contact point
  • ~1.2 mm labial shoulder
  • 1mm above gingival margin
  • Contact cleared with adjacent teeth by ~ 0.5mm

5. Surface Finish

  • Smooth with no sharp angles

6. Path of Insertion

  • Perpendicular to the occlusal plane
  • Does not conflict with adjacent teeth

ORE Undesirable Features

1. Index Preparation

  • Not used
  • Reveals inappropriate reduction

2. Occlusal Reduction

  • Too great / too little reduction occlusally
  • No functional cusp bevel

3. Axial Reduction

  • Too great / too little axial reduction
  • Too great / too little taper
  • Undercut regions present

4. Margin

  • Too wide or shoulder or inverted
  • Too narrow or absent so not continuous
  • Too far above / below gingival margin
  • Not cleared contact with adjacent tooth

5. Surface Finish

  • Rough and pitted

6. Path of Insertion

  • In conflict with tooth structure of adjacent teeth
  • Seating groove incorrectly placed / angled

7. Other

  • Damage to adjacent teeth other than minor grazing

ORE Dental Manikin Exam Guidance

To view or download the official ORE Dental Manikin Exam Guidance document as a separate PDF,  click here . (N.B. when viewing the document outside Dentaljuce, the time you spend reading it will not be recorded.)

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