dentist

2. INTRODUCTION
Pure gold can be used as an restorative material.
Most noble metal, rarely tarnishes in oral cavity
Cold welding property
 Applications
1. Pits and small class I restorations
2. For repair of casting margins
3. For Class II and Class V restorations
4. Repair of cement vent holes in gold crowns

4. GOLD FOIL
• Oldest
• Manufacture:A cast ingot of 15 mm thickness is
beaten to a submicroscopic thickness of 15 or 25
µm
• Supplied as:FIat square sheets of varying
thickness.
No. 4 wt. 4 grains (0.259 gram) 0.51 µm thick.
No. 3 wt. 3 grains (0.194 gram) 0.38 µm thick.

5. Preformed foils:
Ropes & cylinders available in preformed shapes.
Made from No. 4 foil that has been “carbonized”
or “corrugated”
Platinized Foil
Pure platinum foil sandwiched b/w two sheets of
pure gold
Bonded by cladding process
Increases hardness
Available in No. 4 sheet form

6. • Cohesive & Non-Cohesive Gold
Cohesive:
oFor cold welding gold should have a clean surface
oGold attracts gases and any absorbed gas film prevents
cohesion of individual increments of gold
oCohesive gold is supplied free of contaminants
Non-Cohesive:
oGold is subjected to volatile agent such as ammonia,
which is absorbed on surface
oActs as a protective film
oVolatile film readily removed by heating
oRarely used nowadays

7. ELECTROLYTIC PRECIPITATE
Crystalline gold powder is formed by electrolytic
precipitation. Powder is formed into shapes by
sintering(heat fusion).
Available as: mat, mat foil & alloyed
Mat gold:
Crystalline
Formed in strips
Easy to build up the internal bulk, more easily compacted &
adapted
Results in pitted external surface, so covered with a veneer of
foil gold
Mat foil:
Sandwich of electrolytic precipitated gold powder b/w sheets
of No.3 gold foil

8. POWDER GOLD
 Gold powder is enclosed in a No.3 gold foil
 Manufacture:
 Fine powder is formed by chemical precipitation or atomizing the
metal
 Pellets mixed with soft wax, burned off later & wrapped in gold foil
 Available as:
 Foil acts as an effective container and matrix for the powdered
metal
 Powdered gold pellet increases cohesion & reduces time required
for placing it, because each pellet contain more metal by volume tan
same sized pellet of gold foil
 Powdered gold pellets have cylindrical or irregular shape & diameter
of 1 – 2mm
 Ratio of gold foil to powder varies from 1 to 3 for small pellets to 1
to 9 for largest

9. Done to eliminate the need to veneer the restoration
with a layer of foil
No longer marketed
• Alloyed Electrolytic Precipitate:
Newest form is Electraloy RV
Alloy of gold & calcium (0.1 to 0.5% by wt)
Calcium produce stronger restoration by dispersion
strengthening
Alloy sandwiched b/w two layers of gold

10. General principles for cavity
preparation for DFG
• OUTLINE FORM -------
The outline should be smooth and
designed to be esthetically pleasing.

11. Resistance form
 Flat pulpal floors
perpendicular to the
occlusal forces.
 Walls must be smooth
and flat.
 Enamel walls must be
supported by sound
dentin.

12. Retention form
Parallel or slight occlusal
convergence of the
facial & lingual
walls.
Sharp internal line
angles resist the
movement of the
restoration.

13. Convenience form
• Convenience form for direct gold cavity
preparation requires suitable access and a dry
field.
• Width of cavity preparation should be
minimal. Separators may be used to provide
convenience access for class III cavity
preparation.

14. • Sharp internal line and point angles in dentin
serve as convenient starting points for
compacting of direct gold restoration.
• Removing remaining caries. Finishing cavity
walls, debridement and pulp protection.

15. degassing

16. degassing
Electric annealer
Temp.----- 3400 – 3700
Time 5 – 20 min.
Problems-
Pellets may stick together if the tray is moved.
Air current affect uniformity of heating.
Difficult to anneal appropriate amount of gold.
Over sintering.
Greater exposure to contamination.

17. Flame desorption / degassing
Fuel- alcohol or gas.
Heating each piece directly in the
open flame
Alcohol– pure methanol or ethanol
without colorants or additives.
Advantages—
Ability to select piece of gold of
desired size.
Less exposure to contamination
between degassing and use.
Less damage to oversintering.

18. degassing
• Incomplete cohesion.
• Pitting and flaking of the
surface.
• Oversintering and possibly
contamination from tray,
instruments or flame.
• Incomplete cohesion
• Embrittlement
• Poor compaction
UNDERHEATING OVERHEATING

19. compaction
• Hand mallet.
• Pneumatic vibratory
condensers.
• Electrically driven
condensers.

20. condensers
Conventional– single pyramid
shaped face
Current instrument- series of
small pyramidal serrations on the
face.
Serrations- exert lateral forces on
their inclines in addition to
providing direct compressive
forces.
Cut through the outer layers to
allow air trapped below surface
to escape.

21. condensers
• Size
• The lower limit is based on possible
penetration by points of smaller size, which
cause holes in the metal rather than weld it.
• 0.5 mm and 1 mm.
• P= F/A 2 4

22. Pressure application
• Conventional--- mallet
• Recent--- by hand.
• Mechanical gold foil condensers—
– Consists of points that are activated by light blows
that are repeated with frequency that ranges from
360 to 3600 per minutes.
– Vibrations can be produced either pneumatically or
electrically.
– Advantages--- greater comfort to patient and rapid.

23. PROPERTIES OF COMPACTED GOLD
 STRENGTH:-
 Greatest strength-most dense area
 Weakest part- porous area
 In DFG failure occurs from incomplete cohesion, thus transverse
strength is a measure of cohesion
 HARDNESS
 Indicates overall quality
 Indicates presence of porosity
 DENSITY
 Density of pure gold is 19.3gm/cm³
 DFG density less than pure gold because it is not possible to
eliminate voids completely during compaction

24.  EFFECT OF VOIDS
 Amount of voids estimated by apparent density of compacted gold
 Voids on surface, increase susceptibility to corrosion and deposition
of plaque
 Voids at the restoration-tooth interface cause gross leakage and
secondary caries development
 TARNISH & CORROSION
 Resistance to tarnish and corrosion is good if compacted well
 BIOCOMPATIBILITY
 Pulpal response is minimal if compacted well
 This procedure causes a certain amount of trauma to the tooth and
supporting structures
 Mechanical condensor causes less trauma than the manual
technique

25. GENERAL PRINCIPLES FOR DIRECT FILLING GOLD RESTORATION
1. Build up of restoration.
A) Tie formation-
this involves connecting
two opposing point angles
or starting points filled
with gold with a
transverse bar of gold.
This “tie” forms the
foundation for any
restoration in direct gold.

26. GENERAL PRINCIPLES FOR DIRECT FILLING GOLD RESTORATION
 B) Banking of the walls:
This consists of covering
each wall from its floor or axial
wall to the cavosurface margin
with the direct gold material.
Banking should be done
simultaneously on the
surrounding walls of the
preparation.
 C) Shoulder preparation:
This consists of connecting
two opposing walls with the direct
gold material to completely fill up
the restoration.

27. • 2. “Paying” of the restoration
To overfill the preparation, every area of the
cavosurface margin should be individually
covered with excess cohesive gold foil. This
Is condensed with rectangular foot
condenser.
• 3. Surface hardening of the restoration
The rectangular condenser is used with the
highest possible condensation pressure in all
directions on the surface of the restoration
to strain harden the surface gold.

28. • 4. Burnishing
This is done with a suitable burnisher
moving from the gold to the tooth surface.
This enhances the surface hardening and
also produces good marginal adaptation of
the gold.
• 5. Margination:
This step uses sharp gold knives to remove
excess gold from the surface to the tooth.

29. • 6. burnishing:
It is important to burnish the surface of
gold restoration after margination so as
to eliminate marginal discripencies and to
strain harden the surface.
• 7. Contouring :
This step uses knives, files or finishing
burs to create the proper occlusal
anatomy.

30. • 8. finishing and polishing :
Direct gold restorations require very little
finishing if the previous steps are properly
done. It can be done by using tin oxide
powder on soft bristle brushes or rubber
cups.
• 9. final burnishing:
This is done after polishing to make the
surface of the restoration smooth and free
from voids.

31. ADVANTAGES & DISADVANTAGES
• ADVANTAGES
Tarnish and corrosion resistant
Good mechanical properties
Good biocompatibility
• DISADVANTAGES
Poor esthetics
High coefficient of thermal expansion
Manipulation is difficult

32. conclusion
The technique skill of the dentist is of
paramount importance to the success
of the direct gold restorations.
A direct gold restoration of poor quality
can prove to be one of the most
inferior of all clinical restoration.