BY,SMIJAL GM

1. INTRODUCTION2. CLASSIFICATION3. GOLD FOIL4. ELECTROLYTIC PRECIPITATE5. POWDER GOLD6. MANIPULATION OF DIRECT FILLING GOLD7. DESORBING OR DEGASSING8. COMPACTION9. ADVANTAGES & DISADVANTAGES

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 restorations2. For repair of casting margins3. For Class II and Class V restorations4. Repair of cement vent holes in gold crowns

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.

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

Cohesive & Non-Cohesive Gold Cohesive:

o For cold welding gold should have a clean surface

o Gold attracts gases and any absorbed gas film prevents cohesion of individual increments of gold

o Cohesive gold is supplied free of contaminants Non-Cohesive:

o Gold is subjected to volatile agent such as ammonia, which is absorbed on surface

o Acts as a protective filmo Volatile film readily removed by heatingo Rarely used nowadays

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

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

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

There are two process involved1. Degassing 2. Compaction

During storage & packing of cohesive gold, they absorb gasses from atmosphere

Prevents it from fusing Removed by heating- DEGASSING Heating done in two ways

1. In bulk on a tray, by gas-flame or electricity2. Piece by piece, in a well adjusted alcohol flame

Totally dry cavity needed to allow complete cohesion

The gold may be compacted by1. Hand mallet2. Pneumatic vibratory condenser3. Electrically driven condensers

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

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

ADVANTAGES Tarnish and corrosion resistant Good mechanical properties Good biocompatibility

DISADVANTAGES Poor esthetics High coefficient of thermal expansion Manipulation is difficult