Armamentarium for Direct Filling Gold (DFG)

Introduction

1. The gold material itself (in its various forms)
2. Instruments for cavity preparation
3. Instruments for annealing/degassing
4. Instruments for carrying and placing gold
5. Instruments for condensation (compaction)
6. Instruments for finishing and polishing

I. Forms of Direct Filling Gold

1. Gold Foil

• Manufactured by gold-beating (for lightweight sheets) or rolling (for heavier sheets)
• Comes in a book of 1/10 or 1/20 ounces; each book contains 12 sheets with dimensions of 4 x 4 inches
• Numbering system: No. 4 gold foil weighs 4 grains (0.259 g) and is 0.51 µm thick
• Supplied as cohesive (compaction by cold welding) or non-cohesive (surfaces coated to prevent premature welding)
• Foil is rolled into pellets or cylinders before use

2. Electrolytic Precipitated Gold (Mat Gold)

• Produced by electrolytic deposition of pure gold
• Has a spongy, crystalline microstructure that aids cohesion
• Subtypes:
  • Mat gold: Loose crystalline electrolytic gold
  • Mat foil: A sandwich of mat gold between sheets of No. 3/4 gold foil; sintered by heating just below the melting point
  • Gold calcium alloy: Contains a trace of calcium to reduce surface contamination

3. Powdered/Granulated Gold

• Examples: Goldent, E-Z Gold
• Powdered form; compacted by heavy hand pressure using specially designed condensers in a rocking motion (no mallet required for E-Z Gold)
• Useful in areas of limited access

II. Instruments for Cavity Preparation

• High-speed rotary instruments (carbide burs) for initial cavity preparation
• Hand instruments: chisels, hatchets, hoe excavators, and gingival margin trimmers to refine walls
• Cavities for DFG require sharp internal line angles, flat walls, and mechanical retentive features (undercuts) because gold does not bond chemically to tooth structure

III. Annealing/Degassing Instruments

Alcohol Lamp (Annealer)

• The most practical and traditional annealing device
• The gold pellet is passed through the uncontaminated blue flame of an alcohol lamp until it reaches cherry-red heat
• Immediately air-cooled and placed in the cavity
• As a side effect, the gold is sterilized

Electric Annealer

• A coiled wire element that heats to incandescence
• Used as an alternative to the alcohol lamp; provides controlled, consistent heat

The gold must be annealed freshly just before each increment is placed; pre-annealed gold left exposed for even a short period will pick up surface contamination.

IV. Gold Carrying and Passing Instruments

Passing Instrument / Gold Carrier

• A small bi-angle explorer with the point broken off makes a practical instrument for passing gold through the annealing flame and into the cavity
• Dedicated gold carriers (tweezers/tube carriers) are also available to pick up, transport, and deposit pellets of gold into the preparation
• Tube-type carriers allow pellets of specific sizes to be loaded and ejected directly onto the cavity floor

V. Condensation (Compaction) Instruments

A. The Condenser (Gold Plugger)

• Handle: Receives mallet blows (for hand-malleted condensers, ~6 inches/15 cm long with a blunt end)
• Shank: Straight, monoangle, offset, or binangle
• Nib (working tip): The active condensing face; all nibs are serrated with a pyramidal configuration to grip the gold

B. Methods of Condensation and Associated Instruments

1. Hand Pressure Condensation

• Used as the first step (initial confinement) of E-Z Gold and powdered gold
• Similar to amalgam condensation but with greater force and duration
• Specially designed hand condensers with wide nibs are used

2. Hand Malleting (Most Preferred)

• The oldest and most preferred method by experienced clinicians
• Requires a trained chairside assistant
• The dentist holds the condenser and directs it precisely; the assistant delivers light, bouncing mallet blows to the handle
• Requires coordination and practice; four-handed technique

• Typically a small, weighted metal or plastic head mallet
• Delivers controlled, variable-force blows
• Advantage: greatest control of force, rapid change of condenser nibs

3. Automatic Hand Condenser (Spring-loaded)

• A spring-loaded instrument delivering a series of regulated blows by releasing a spiral spring
• Advantage: well-regulated, repetitive blows
• Disadvantage: blow descends before full operator pressure is applied

4. Pneumatic Condensation (Hollenbeck Pneumatic Condenser)

• Developed by Dr. George M. Hollenbeck
• Consists of an electric engine driving an air condenser; compressed air is delivered through a thin tube to the handpiece
• The condenser vibrates/reciprocates, energized by compressed air
• Advantage: frequency and intensity of blows can be controlled, reduces operator fatigue, no assistant required

5. Electronic Malleting (Electro-Mallet)

• McShirley Electro-Mallet (McShirley Products, Glendale, CA) - no longer manufactured
• An electrically driven reciprocating handpiece delivering controlled blows at set intensity and frequency
• Advantage: no dental assistant required; intensity is controllable
• Note: Must be used at the manufacturer's recommended intensity to avoid pulpal irritation

VI. Finishing and Polishing Instruments

1. Removal of Excess Gold

• Rotary instruments: finishing disks, finishing burs
• Remove gross excess and contour the restoration

2. Elimination of Surface Pits and Voids

• Burnishing hand instruments: beaver-tail burnisher, gold knife, discoid carvers, gold files
• Surface pits exposed during polishing (from minute air voids) are burnished closed

3. Polishing

• Fine garnet disks, cuttle disks, abrasive strips
• Pumice and powdered chalk for final luster
• The goal is a smooth, highly lustrous surface resistant to tarnish and corrosion

VII. Ancillary Equipment

Summary Table: Complete Armamentarium

References

1. Roberson TM, Heymann HO, Swift EJ Jr. Sturdevant's Art and Science of Operative Dentistry, 5th edition. Mosby, 2006. Chapter 18: Direct Gold Restorations.
2. Baum L, Phillips RW, Lund MR. Textbook of Operative Dentistry, 3rd edition. W.B. Saunders, 1995.
3. Ferrier WI. Gold Foil Operations. American Academy of Gold Foil Operators. Available at: goldfoil.org
4. Sockwell CL, Tilliss TSI. Direct Gold Restorations. In: Sturdevant's Art and Science of Operative Dentistry. Chapter 22. Also available via Pocket Dentistry.
5. Journal of the Massachusetts Dental Society, Summer 2019. Gold Foil: A History of Excellence. Available at: mydigimag.rrd.com
6. Billa M. Direct Filling Gold - Presentation. Available at: SlideShare
7. American Academy of Gold Foil Operators. goldfoil.org