Shade Selection
Recommended Shade Guides: Vita Lumin Shade Guide.

GENERAL CONSIDERATIONS

Technique Tips

  • Ensure even reduction of the anatomic form.
  • Provide enough room for the ceramic to allow adequate strength.
  • Sharp transitions and sharp internal edges/line angles or undercuts MUST be avoided.
  • Margins should have a pronounced chamfer or shoulder with butt joint margins. Avoid tapered margins, feathered edges or bevelled shoulders.
  • Ensure there is an adequate path of insertion.

Suggested Margin Preparation

 
  • Shoulder with rounded axio-cervical line angle, uniform circular ablation.
  
  • Chamfer preparation (with reduced mechanical support of the crown). Particularly used with reduced substructure (e.g., after repeated crowning).

Common Preparation Errors

  1. Insufficiently defined and finished preparation margins.
  • Uneven preparation limit ("gutter" preparation, vertical unevenness).
  • Irregular marginal reduction of layers (horizontal unevenness).
  • Wrong shape of preparation limit.
  • Unnecessarily deep subgingival preparation.
  • Preparation in root dentin.
  1. Poorly controlled tooth reduction.
  • Excessive reduction, especially in the upper anterior teeth (vestibular) and premolars.
  • Excessive incisal/occlusal reduction causing reduced retention and stability.
  • Insufficient reduction at the palatal side of the upper anterior teeth (malfunction occlusion).
  • Excessive taper.
 
  • Incorrect preparation of the labial surface: Preparation in one plane; therefore insufficient reduction of substance. Fracture of the crown may result due to insufficient wall thickness of the crown.
  
  • Incorrect preparation of the labial surface, risk of damage to the pulp.

Preparation Tips

POSTERIOR PREPARATION

Since the scanner's tip is rounded, the finish line should be a chamfer placed subgingivally at 0.5 to 0.7 mm. A rounded shoulder may also be an appropriate design.

A relatively level topography should be accomplished during preparation of the occlusal surface of posterior dentition.

The occlusal surface of a posterior tooth is shaped, eliminating undercuts and sharp edges. Steep slopes and sharp grooves are avoided to enable the scanner to recognize all of the information provided through the tip.

ANTERIOR PREPARATION

For anterior dentition, preparation of the lingual surface requires shaping with a diamond bur to provide space for crown contour and retention.

Fine finish lines on the prepared tooth enable the scanner to precisely register all aspects of the die models, directly affecting the marginal fit of the definitive restoration.

PROCERAŽ AllCeram Preparation Tips
John N. Nasedkin, DDS, MRCD (C)

As with any restoration, proper and careful planning and preparation is the key to success. The following tips are just some of the critical considerations that I have found work well in my practice:

  1. Make your shade selection beforehand. Procera has a translucent substrate that effectively blocks most tooth stains. The AllCeram porcelain is high in chroma and gives particularly vital restorations.
    2.
  2. Make depth cuts with cylindrical diamonds on the facial surface of upper anterior teeth in two planes - finish above the gingival tissues.
    3.
  3. Use a wheel-shaped or football diamond to reduce the lingual surface of upper anteriors to insure adequate contour and reduction.
    4.
  4. When tooth loss is extensive, place directed shrinkage foundations as a build-up and block out undercuts - use self-cure composite for this purpose.
    5.
  5. Place a thin margin deflection thread and then finish with a Brasseler 8879 .014 or .012 diamond for the final marginal chamfer.
    6.
  6. Use the Flexible Clearance Gauge from Belle de St. Claire to insure 2 mm of occlusal clearance.
    7.
  7. Make sure your preparations have rounded contours only, no sharp angles.
    8.
 

Two plane proximal reduction with round-ended diamond to above gingival margin.

  

Finishing step: thin deflection thread is placed in the gingival sulcus and Brasseler finishing diamond 8879-014 is used to define the chamfer margin.

Refinement of tooth preparation for Procera crown with Procera chamfer diamond. NOTE: thin deflection cord in place. Finish with Brasseler 8879-014 fine diamond then place retraction thread. Remove retraction thread prior to impression making.

  1. Shrink wrap the prepared teeth before or after the impression. Use alcohol in a pellet and rub to remove the air-inhibited layer. The polymer coating protects the tooth and reduces sensitivity. Take full arch impressions of prepared teeth and of the opposing arch.
    2.
  2. Reline your provisional(s) for more accurate marginal fit. Use non-eugenol temporary cement. This will mean fewer insertion problems.
    3.
  3. Allow additional time for laboratory fabrication - the process takes longer than normal.
    4.
  4. When the prepared tooth is short and requires length extension, advise your lab to wax the coping to full contour, cut-back by 1.25 and provide an inside-outside scan to the processing facility in order to insure that the porcelain is adequately supported.
    5.
  5. With root-filled teeth, use a quartz and carbon fibre post (such as Aestheti-post) and tooth-coloured core material.
    6.

Fractured upper left central incisor.

Procera crown at one year follow-up.

Reprinted with permission of Nobel Biocare. Procera is a registered trademark of Nobel Biocare.

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