Gold Castings: An Overview

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Gold Castings An Overview

• DDS Class of 2007
• Rio Hondo Simulation Lab
• January 8, 2005

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Quote for the Day

• "Have patience with all things, but chiefly have
  patience with yourself. Do not lose courage in
  considering your own imperfections, but instantly
  set about remedying them every day begin the
  task anew."
• Saint Francis de Sales

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Gold Alloy Castings

• What are they?
• One-piece restorations made of a gold alloy
  that are constructed by use of the lost wax
  process.

They can cover very little of the tooth/teeth or
the entire clinical crown depending on the
particular need situation.
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Indications for Castings

• Castings are indicated in many different
  situations.
• A casting is an ideal restoration for a Class II
  carious lesion given all other considerations
  (periodontal, caries risk, patients home care,
  etc) are favorable. A casting would also be
  ideal for a tooth so decayed that it required
  endodontics and an amalgam build-up. Cracked
  tooth syndrome, Missing Cusps, etc., etc., etc.

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Weighing the Options

• Advantages
• One-piece construction is theoretically more
  durable than a PFM crown.
• Clinical success of over 50 years in some cases.
• Can be a very conservative treatment.

• Disadvantages
• Esthetics?!
• Can be a very extensive treatment as well.
• Done poorly, this is a bad restoration.

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Treatment Planning and Preparation Considerations

• Nature of Opposing Occlusion
• Desired Final Contour of Restoration or
  Intra-arch Harmony
• Material Bulk Usage Requirements
• Path of Insertion

• Existing Tooth Conditions
• Extent of Defective Structure/Disease
• Biological Width
• Periodontal Health
• Endodontic Considerations

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Casting Nomenclature

• Inlays, Onlays, and Inlay-Onlays
• Cuspal coverage is the determining factor.
• MOD Onlays, 3/4 Crowns, and 7/8ths Crowns
• Are named according to the coverage of the axial
  surfaces and are some examples of partial veneer
  crowns.
• (Regular) 3/4 Crowns
• always cover the lingual axial by definition.
• Reverse (3/4 or 7/8ths) crowns
• cover the buccal axial surface instead of the
  lingual.
• Full Coverage Crowns
• Are commonly called Complete Veneer Crowns (CVC),
  Full Gold Crowns (FGC), (PFMs,etc.)

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Casting Preparation Criteria

• Outline
• Is the line created where your preparation ends
  circumferentially.
• Basically, the outer limit of the preparation
• Is measured and compared to an adjacent tooth,
  the crest of the free gingival margin, or other
  landmarks.

• Internal
• Is a measure of how much reduction was made to
  accommodate the restorative material.
• Also considers the path of insertion and any
  build-up or base materials.
• Usually compared to the opposing and/or adjacent
  teeth, or referenced from the external of the
  tooth.

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Casting Preparation Criteria

• Retention
• It is a measure of the ability of the restoration
  to within stand dislodging forces. Commonly
  includes resistance as well as retention.
• Primarily a measure of the degree of parallelism
  between retentive walls and length of the
  retentive walls. Secondarily, the surface area,
  and lastly, surface texture.
• Walls that are over-tapered or only 2.5 mm tall
  can be augmented by use of a groove, box form, or
  countersink. Pins are a last resort.

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Casting Preparation Criteria

• Cavosurface Finish and Margins
• Creates a circumferential and continuous area
  which increases the ability of the restoration to
  fit snugly to the tooth to minimize microleakage
  underneath while keeping both the tooth and
  restoration as strong as possible.
• Is measured by the smoothness, continuousness,
  the appropriate width and angulation/direction of
  the feature compared to the external of the tooth
  (commonly bevels and flares).
• This category also grades the cleanliness of the
  preparation and adjacent oral structures.

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Rules for CreatingCasting Preparations

• Outline
• Minimally extend past all defects (0.5 mm)
• Clinically, gingival separation from adjacent
  teeth is minimally 0.5 mm. There is no ideal or
  maximum.
• Pre-clinically, gingival extension will be
  measured on the buccal and lingual by some
  arbitrary distance (usually 0.65 mm) from the
  crest of the gingiva. Interproximal extensions
  should not be measured pre-clinically, but the
  outline should roughly follow the shape of the
  gingiva and end supra-gingivally.

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Rules for CreatingCasting Preparations

• Outline
• Clinically, one would gingivally extend as far as
  needed to create a retentive, defect inclusive
  preparation, without encroaching on the
  biological width.
• Flare extensions are measured somewhere between
  the mid-point and top of the flare.
• For esthetic areas (any MB Maxillary flare
  extension) the ideal is 0.5 mm with a range of
  0.25 to 0.65 mm
• For all other flared areas (non-esthetic), the
  ideal extension is 0.75 mm with a range of 0.5 to
  1.0 mm.

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Rules for CreatingCasting Preparations

• Internal
• Path of Insertion must allow the insertion and
  removal of the restoration past the adjacent
  teeth and provide for an even amount of reduction
  to the tooth wherever possible.

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Rules for CreatingCasting Preparations

• Internal
• Reduce the occlusal surface relatively evenly, so
  the crown will be able to handle occlusal forces
  and so it looks like a shorter likeness of the
  tooth.

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Rules for CreatingCasting Preparations

• Internal
• Partially covered cusps are always reduced using
  a football-shaped diamond bur for slightly
  increased bulk of gold and partial buttressing of
  the finish line

Shank of Bur is parallel to triangular ridges
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Rules for CreatingCasting Preparations

• Internal
• Planes are created on a preparation to allow for
  proper contour for the final restoration and
  sufficient bulk of gold to within the occlusal or
  deforming forces they will encounter.
• Mesial Distal surfaces only have 1 plane (or a
  first plane).
• Buccal Lingual Surfaces will have 2 or 3 planes
  depending on the curvature of the tooth.
• Basically, functional cusps will have 3 planes
  and non-functional cusps only 2 planes in a full
  coverage restoration.

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Rules for CreatingCasting Preparations

• Internal
• Planes 30 PFM Preparation Mesial View

Buccal has 3 Planes Mesial (and Distal) have
only 1 plane
Lingual has 2 Planes
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Rules for CreatingCasting Preparations

• Internal
• Make sure that the mesial and distal areas of the
  preparation by the adjacent teeth marginal ridges
  allow for enough bulk of gold.
• Bases versus Build-ups.
• Bases just fill in space and cannot be relied
  upon to provide any retention.
• Build-ups are stronger materials that are
  mechanically locked into/onto the tooth which can
  be used to provide additional retention.

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Rules for CreatingCasting Preparations

• Internal Reduction Guide
• Gingival Axial - 0.65 mm (0.5-0.8 mm)
• Mid-Axial 1.0 mm (0.751.25 mm)
• Occlusal
• Non-Functional Maxillary Cusp 0.5 mm
• All Other Cusps 1.50 mm (1.00-1.75 mm) for all
  gold
• Pulpal Depth 2.00 mm (1.50 mm min) prior to
  occlusal reduction
• Box Forms 1.30 mm axially (1.00-1.75 mm)
• Shoulders 1 mm axially 1 mm tall at highest
  point prior to beveling

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Rules for CreatingCasting Preparations

• Internal Reduction Guide

Occlusal reduction 1.5 mm (1.0-1.75 mm) gold
Functional Cusp Buccal reduction for bulk
contour
2nd plane for bulk and contour
Shoulder (1 mm tall and 1 mm axial depth) for
buttressing and cuspal protection
Mid Axial Reduction 1.0 (0.75 1.25 mm)
Gingival axial 0.65 mm (.5-.8mm)
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Rules for CreatingCasting Preparations
Remaining Isthmus acts as part of staple effect
for retention

• Internal Reduction Guide

Occlusal reduction follows original/desired
anatomy
1 mm tall and 1 mm axial depth Shoulder for
buttressing and cuspal protection
Proximal Walls 0.65 mm in gingival for retention
Box Form Axial Reduction 1.3 mm (1.0 1.75 mm)
Buc Ling Prox walls must be near parallel for
retention
Non-functional cusp Bevel 1.0 mm no range
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Rules for Creating Casting Preparations

• Retention
• 6-10 degrees of parallelism of opposing retentive
  walls is ideal with a range of 3-15 degrees
  coupled with.
• Ideal retentive wall length of 3-4 mm with a
  minimum of 2.5 mm (no max. overextended)
• Retentive wall length can be obtained through
  axial walls, boxes, or grooves. Grooves have
  less surface area and are thought to be only
  slightly less retentive.

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Rules for Creating Casting Preparations

• Retention
• With a minimum 2.5 mm wall, you can supplement
  the retention with grooves, boxes, or
  countersinks (aka secondary retentive features)
  to replace deficient wall.

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Rules for Creating Casting Preparations

• Retention
• When walls are over-tapered, you can add a groove
  that is in the proper path of insertion to
  augment the retention in the appropriate wall.
  Grooves that follow the over-tapering add little
  or no retention. That means the groove will get
  shallower axially as it comes occlusally.
• Grooves and Boxes must be placed axially enough
  to create near parallel opposing walls to be
  effective (min. 0.65 at the gingival area).

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Rules for Creating Casting Preparations

• Retention
• All together, the retentive features must form a
  circumferential-like hold of the tooth.
• Partial veneers form this hold by the Staple
  Effect of the two box forms and the
  isthmus/offset.

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Rules for CreatingCasting Preparations

• Cavosurface Finish and Margins
• Commonly referred to as finish lines.
• This is done in a horizontal plane with bevels
  or chamfers and in a vertical plane with
  flares. Junctions between the horizontal and
  vertical are smooth transitions, not abrupt in
  any way.

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Rules for CreatingCasting Preparations

• Cavosurface Finish and Margins
• Bevels
• 0.65 mm wide evenly smooth (range 0.5-0.8mm).
• Angulation should be 45 degrees at the external
  of the tooth (range 30-60 degrees)
• Maxillary esthetic cusps are bevels 0.5 mm wide
  at 90 degrees to decrease gold visibility.
• Mandibular non-functional (lingual) cusps have a
  1.0 mm wide bevel on partially veneered cusps due
  to proximity to increased occlusal forces.

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Rules for CreatingCasting Preparations

• Cavosurface Finish and Margins
• Flares
• Are in a nearly vertical direction that allows
  the restoration to seat along the path of
  insertion.
• This normally requires the flare to get larger as
  it comes occlusally to some extent.
• These are also placed at an angulation of 45
  degrees to the surface of the tooth. No range
  specified.
• Take some practice

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Rules for CreatingCasting Preparations

• Cavosurface Margins Guide

Flares get wider as they come occlusally
Occlusal functional cusp bevel 0.65 mm (0.5-0.8mm)
Junctions are smooth and continuous
Gingival bevels 0.65 mm (.5-.8mm)
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Rules for CreatingCasting Preparations

• Cavosurface Margins Guide

Flares get wider as they come occlusally and are
fully visible along the path of insertion.
Occlusal functional cusp bevel 0.65 mm (0.5-0.8mm)
Junctions are smooth and continuous
Flares form a 45 degree angle to the external
surface
Non-functional cusp bevel 1.0 mm due to proximity
to occlusion
Gingival bevels 0.65 mm (.5-.8mm)
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Rules for CreatingCasting Preparations

• Buttressing Effect
• Because these finish line areas are thinned out
  and burnishable/malleable, they are more subject
  to deformation under occlusal stress.
• To counteract these stresses, a bulk of gold is
  often place very close to these finish lines to
  help absorb the occlusal forces and increase the
  long term marginal seal.
• This can be done with a groove, shoulder, and/or
  an offset.

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A Note on Grooves

• Grooves are placed in gold preparations for two
  main reasons which determine their qualities.
• Retentive grooves have one long plane and are
  prepared in the proper path of insertion.
• Buttressing grooves may have more than one plane
  (for even bulk) and is placed at a point near the
  finish line it is supporting.
• A groove may serve both purposes.

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Special Thanks to

• Dr. Boris Keselbrener for opening his vault of
  pictures for me to use in this presentation.
• Dr. Richard Kahn for his pictorial contributions
  and mentorship.

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Clinical Situations/Preps

• 20 MOD Onlay
• 30 CVC
• 13 and 18 ¾ Crowns
• 31 Reverse Mandibular ¾ Crown
• 14 7/8ths Crown
• 29 CVC out of alignment
• 5 MOD Onlay Under-erupted