CHAPTER 17: DIRECT GOLD RESTORATIONS

Direct Gold

a gold restorative material that is manufactured for compaction directly into prepared cavities

is inserted into tooth preparations under force. The purpose of the force is to wield the gold into restorations containing minimal porosity or internal void spaces

may be cohesive or noncohesive

All direct-filling gold are “compactable”

• They can be inserted into the tooth preparations under force and compacted

• They can be condensed into preparation lines and point angles and against preparation walls

Advantages of direct gold

• Can last for a lifetime

• Surperb biocompatibility of gold with the oral environment

• Excellent marginal integrity

disadvantages of direct gold

• Extremely technique-sensitive

• Time consuming

• Costly

• Galvanic Potential

Indications of direct gold restorations

• Treatment of small lesions and defects in teeth with sound pulpal and periodontal health

• A defective margin of an otherwise acceptable cast-gold restoration also may be repaired with direct gold

contraindications of direct gold restorations

• Teeth with large pulp chambers.

• Severely periodontally weakened teeth with poor prognosis.

• Patients with economic limitations.

• Handicapped patients unable to tolerate long dental appointments.

• Root canal–treated teeth, since they are brittle (exception: sealing access cavities in cast-gold restorations).

2 types of direct gold

gold foil

powdered gold

2 form os gold foil

pellet form

cylinder form

Pellet form

Foil piece is folded at the corners, rolled into a pellet

Cylinder form

- Rolled from sheet segments;

18% ammonia

Preferential contamination to prevent deleterious oxides from forming on the gold until it is used.

POWDERED GOLD

• Combination of chemical precipitation and atomization, with an average particle size of 15 mm

• Atomized particles are mixed together in wax, cut into pieces, and wrapped in No. 4 or No. 3 foil.

• This product is marketed as Williams E-Z Gold.

Wielding —

wielding occurs because pure gold with an absolutely clean surface coheres as a result of metallic bonding.

For a successful welding to occur during restoration, the gold must be in a cohesive state before compaction, and a suitable, biologically compatible compacting force must be delivered.

Noncohesive direct gold

is due to the presence of surface impurities or wax

E-Z Gold pellets

are supplied with a wax coating (must be burned off before compaction)

heated above the ethanol flame until wax ignition

To remove the wax coating and render the gold surface cohesive before insertion.

DEGASSING / ANNEALING

the process of removing gases from the surface of the gold before dental compaction.

• This is accomplished by

  • heating the gold foil on a mica tray over a flame

  • Electric annealer

  • heating each piece of gold over a pure ethanol flame.

• The advantage of using pure ethanol flame is that each piece of gold is selected and heated just before insertion, and waste of gold is avoided

All direct-filling gold products are degassed immediately before use except when noncohesive foil is specifically desired.

Underheating

fails to render the gold surface pure.

gold remains noncohesive

Overheating

may cause the gold to become brittle or melt and render it unusable.

gold becomes brittle or melts, making it unusable.

Gold Foil Degassing

The gold is passed into the blue inner core of the flame on the tip of a foil-passing instrument and held just until the gold becomes dull red

E-Z Gold Degassing

The E-Z Gold pellet must be heated ½ to 2.5 cm (1 inch) above the ethanol flame until a bright flame occurs

Purpose of compaction:

Compact gold into a dense, void-free, cohesive restoration.

Weld increments of gold into a solid cohesive mass (via metallic bonding).

Wedge gold firmly against preparation walls and into line/point angles

principles of compaction

• Line of Force: Compaction force must be directed into the preparation (90° to pulpal floor, or at 45° to walls).

• Results: Removes porosity, locks gold against walls, minimizes voids at cavosurface margins.

• Precautions:

  • Avoid excessive pulpal irritation by using light, controlled malleting.

  • Ensure dense condensation especially at cavosurface to prevent leakage.

CONDENSERS

vary in nib size (0.4–0.55 mm ideal).

• Smaller nib = ↑ compaction force; BUT too small may punch holes.

• Larger nib = less effective in forcing the gold into angles in the tooth preparation.

Round condensers

— (0.4 to 0.55 mm) in diameter

Varney foot condenser

(1 to 1.3 mm,) which has a rectangular face

Parallelogram condensers

— only used for hand pressure compaction (~0.5 to 1mm)

HAND MALLET

Requires an assistant for the procedure.

Allows great control of malleting forces when variations are called for.

Allows for rapid change in condenser nibs, or tips, when a multitude of condensers is required.

ELECTRO-MALLET

aka: PNEUMATIC MALLET

Does not require a dental assistant for the procedure.

Condensers of Electro-mallet consist of a nib or working tip, and a short shank (~ 2.5 cm in length) that fits into the malleting handpiece.

COMPACTION TECHNIQUEs for GOLD FOIL

• Compaction begins when a piece of gold is placed in a tooth preparation

• begin malleting in the center of the mass

• the most efficient compaction occurs directly under the nib face.

• Line of force is important when any gold is compacted (the direction in which the condenser is aimed)

• Correct hand-malleting requires a light, bouncing application of the mallet to the condenser

COMPACTION TECHNIQUEs for E-Z GOLD (POWDERED GOLD)

• Using an amalgam or a gold foil condenser, the first pellet of E-Z gold is pressed into the depth of the tooth preparation

• a small condenser is selected to thrust and wedge the goild unto the line angles and walls

• To avoid creation of large void spaces in the restoration, a dense, fully condensed surface is obtained with each pellet before subsequent pellets are added.

OUTLINE FORM of direct gold restorations

• Include all pits, fissures, and defects.

• Margins must be smooth, not ragged.

• Outline should be esthetic if visible.

resistance FORM of direct gold restorations

• Walls oriented to withstand occlusal forces.

• Flat pulpal/axial walls, enamel supported by dentin.

retention FORM of direct gold restorations

• Parallel or slightly converging walls for mechanical lock.

• Sharp internal line angles in dentin resist movement.

• Depth: ~0.5 mm into dentin for Class I, ~0.75 mm from cementum in Class V.

CONVENIENCE FORM of direct gold restorations

• Adequate access for condensers.

• Rubber dam isolation mandatory.

• May use separators (Class III) or gingival retractors (Class V).

• Sharp point angles aid compaction starting points.

CLASS I GOLD RESTORATIONS

• Outline: small, conservative; circular, oblong, triangular depending on lesion.

• Instrumentation: No. 330 or No. 329 bur is used for occlusal preparation

• Walls: generally parallel; slight divergence mesially/distally to protect ridges.

• Depth: uniform pulpal wall, ~0.5 mm into dentin.

• Undercuts: placed incisally/gingivally for retention (esp. lingual surfaces of incisors).

• Bevel: small cavosurface bevel for finishing.

• Restoration: gold foil or E-Z Gold pellets compacted incrementally; mallet or hand pressure; finish with burnishing, disks, pumice, tin oxide.

CLASS III GOLD RESTORATIONS

• Approach: usually lingual for esthetics; sometimes facial.

• Outline: smooth, esthetic, includes lesion but avoids weakening incisal edge .

• Internal form: flat axial wall (0.5 mm into dentin); sharp axiofacial/lingual line angles.

• Retention: gingival wall slopes inward (acute axiogingival angle); incisal undercut in dentin for mechanical lock .

• Variations: mandibular incisors require modified prep due to small size and contact near incisal edge .

• Restoration: incremental compaction of small pellets; special condensers used to fill incisal/gingival undercuts; separation aids finishing contacts .

• only pellets of gold is used for this restoration.

CLASS V GOLD RESTORATIONS

• Operating field: rubber dam, often with No. 212 retainer for gingival retraction .

• Outline: curved to follow gingival contour for esthetics .

• Walls: gingival wall beveled (when indicated); axial wall 0.5 mm into dentin; occlusal/gingival walls may provide retention.

• Instrumentation: hand instruments refine walls and create acute axiogingival line angle.

• Restoration: compact medium/large pellets centrally, small ones at margins; cover all cavosurface margins before building convexity.

• Finishing: burnish, disks, gold knife/discoid-cleoid for margins; polish with pumice, tin oxide, white rouge .