Direct filling gold
Dr. Zameer Pasha
Objectives
History
Classification—foil
elecytrolyte precipitate
granular gold
cohesive – non cohesive
Properties
Advantages & Disadvantages
Indications and Contraindications.
History
1483--- Giovanni d’Arcoli--- gold leaf
filling
Early 19th centuary---- gold leaf
became popular in United States.
1812--- Marcus Bull---- beaten gold
for applications.
History
1853---- sponge gold introduced in
United States and England to replace
gold leaf.
1855--- cohesive, or adhesive gold
introduced by an American dentist
Robert A. Arthur.
Why gold???
Gold was one of the earliest materials
available for the restoration of teeth.
Direct gold are those gold restorative
materials that are manufactured for
directly compacting them into
prepared cavities.
Why gold???
This noble metal is a superior restorative material
for small lesions and defects of teeth.
Direct gold restorations are highly durable if
proper case selection , cavity preparation and
careful manipulation of the material done.
Direct gold restorations exhibit excellent marginal
integrity and biocompatibility in the oral cavity.
TYPES OF DIRECT FILLING GOLDS
There are several forms of direct gold available for
restorative purposes. All of them are cohesive and
99.99% pure.
Direct filling gold may be categorized as follows
Foil
A.
Sheets ( cohesive & non
cohesive)
Pallets (hand rolled and
preformed)
C.
Cylinders.
D.
Corrugated foil.
E.
Platinized foil.
F.
Laminated foil
II. Electrolytic precipitated gold
A.
Mat gold
B.
Mat foil.
C.
Gold calcium alloy
III.Powdered gold
A.
Goldent
Gold foil - sheets
Also called as fibrous gold.
Standard no. 4 gold foil is
supplied in 100 x 100 mm ( 4x
4 inch ) sheets that weight 4
grains( 0.259 grams) and 0.51
micro meter in thickness.
No. 3 foil--- 3 grains in weight (
0.194 grams) and 0.38
micrometer in thickness.
Gold foil cylinders
Produced by rolling cut segments of no.
4 foils into a desired width –
3.2 mm
4.8 mm
6.4 mm
Platinized gold foil
Two sheets of no. 4 pure gold foil and a
layer of pure platinum foil sandwiched
between them can be hammered until the
thickness of no. 4 foil is achieved.
or
Layers of platinum and gold can be bonded
together by a cladding process during the
rolling operation and thus the sandwich is
already welded together before hammering
procedure begins.
Electrolytic precipitate
mat gold
Microcystalline gold powder formed electrolytic
precipitation– also called crystalline, mat or
sponge.
Mat gold is electrolytically precipitated crystalline
form that is sandwiched between sheets of gold
foil and formed into strips.
Alloyed electrolyte precipitate--Granular gold alloyed with 0.1% calcium.
Calcium increases the strength.
Granular (powdered gold )
Fine powder is formed by chemical
precipitation or atomizing the metal.
Particle size ---maximum 74
micrometer and average particle
size is 15 micrometer.
Foil forms an effective container for
the powdered metal and forms
pellets of 1- 2 mm in diameter
Each pellet contains ten times more
more metal by volume than are
comparable sized pellet of gold foil.
Cohesive & non cohesive gold
For cold – welding gold should have a clean
surface free from impurities. Gold attract
gases eg. Oxygen, to its surface and any
adsorbed gas film prevents cohesion of
individual increments of gold, during their
compaction.
Cohesive gold --manufacturer therefore supplies the gold
essentially free of surface contaminants,
and thus inherently cohesive. This type of
gold is known as cohesive gold.
Non – cohesive gold---Manufacturer can subject the foil to a
volatile agent such as ammonia, which is
adsorbed on surface of gold. This volatile
substance acts as a protective film to
prevent adsorption of non volatile materials
and premature cohesion of pellets in their
container. This ammonia treated foil is
called as non – cohesive gold.
PROPERTIES OF DIRECT FILLING GOLD
Pure gold is soft, malleable and ductile and
does not oxidize under the normal
atmospheric conditions.
It has rich yellow colour and strong metallic
lusture.
Brinnel hardness number of gold is 25. this
makes it very soft. During compaction the
hardness increases.
Gold is the noblest of all the metals. It does
not undergo tarnish and corrosion in the
oral environment.
PROPERTIES OF DIRECT FILLING GOLD
Most important property which has enabled
it as a direct restorative material is its
ability to be cold welded at room
temperature. When two pieces of gold are
firmly pressed together under sufficient
force at mouth temperature they fused
together.
Gold exhibits excellent marginal integrity
and biocompatibility with the oral tissues.
Coefficient of thermal expansion of gold is
14.4 8* 10-6 which is close to that of tooth
structure 11.4* 106.
Advantages of direct gold--When properly placed direct gold is
the most durable material.
It does not undergo tarnish and
corrosion in the oral cavity.
Insoluble in oral fluids annd coefficient
of thermal expansion is similar to
tooth.
Its manipilation is atraumatic to the
dental pupl and supporting structures.
Advantages of direct gold--It exhibits good adaptation to the
cavity walls and can be burnished
against the cavity margins to create
excellent marginal integrity.
Plaque accumulation is negligible on
direct filling gold restorations.
Density and hardness of compacted
gold provides adequate compressive
strength.
disadvantages
Colour yellow
Manipulation is technique sensitive.
Filling cavity is time consuming.
Expensive.
High thermal conductivity. Pulp
protection is required.
Galvanic shock.
Indications
Class I
Class II
Class III
Class V
Class VI
Defective crow margins.
Contraindications
Young patients
Heavy occlusal forces
Periodontally compromised tooth.
Economics
Handicapped and children of special
needs
Esthetics access and isolation
difficulties.
references
Philip’s Science of dental materials 11th
edition by Kenneth J. Anusavic