Direct Filling Gold

DIRECT FILLING GOLD

A seminar by:

Dr. SHWETA SHARMAPostgraduate Student

DEPARTMENT OF CONSERVATIVE DENTISTRY AND ENDODONTICS

S.D.M. COLLEGE OF DENTAL SCIENCES & HOSPITAL DHARWAD

MARCH 2008

1

DEPARTMENT OF CONSERVATIVE DENTISTRY AND ENDODONTICSS. D. M. COLLEGE OF DENTAL SCIENCES AND HOSPITAL, DHARWAD,

KARNATAKA, INDIA

CERTIFICATE

This is to certify that the seminar entitled “DIRECT FILLING GOLD” is

presented by Dr. Shweta Sharma in partial fulfillment of the requirement for the degree

of Master of Dental Surgery (M.D.S.) in Conservative Dentistry and Endodontics, under

our guidance during the period 2005-2008.

Dr. K.H. Kidiyoor, M.D.S.

Professor & HODDepartment of Conservative Dentistry & Endodontics

Dr. Priya Horatti, M.D.S.

Professor & Guide Department of Conservative Dentistry & Endodontics

2

DIRECT FILLING GOLD

CONTENTS

HISTORY

PROPERTIES OF PURE GOLD

BIOCOMPATIBILITTY

TYPES

ANNEALING/DEGASSING

INDICATIONS AND CONTRAINDICATIONS

ADVANTAGES AND DISADVANTAGES

CONDENSATION

CAVITY PREPARATION AND RESTORATION

3

HISTORY

About 3000B.C – Greeks and Romans used gold foil for jewelry

Between 3000 and 2000 B.C – Gold jewelry was found in Sumerian,

Babylonian, and Assyrian tombs

Between 1570 and 1293 B.C – Gold jewelry was found in Egyptian tombs

In 1483 – Giovanni d’Arcoli recommended gold-leaf fillings

Philip Pfaff, dentist to Frederick the Great of Prussia, used gold foil to cap the

pulp

Early 19th century – Gold leaf as a restorative material became popular in the

United States

In 1812 – Marcus Bull of Hartford, Connecticut, began producing beaten gold

for dental applications

In 1853 – Sponge gold was introduced in the United States and England to

replace gold leaf

In 1855-American dentist Robert A. Arthur introduced cohesive or adhesive

gold

4

PROPERTIES

Soft, malleable, ductile

Does not oxidize under normal atmospheric conditions

Rich yellow in colour with a strong metallic lustre

Fuses at a temperature of 1063°C and boils at 2200°C.

True density of pure gold is 19.0 – 19.3g/cm3.Measured density is in the range

of 14-15 g/cm3

Brinell’s hardness number of pure gold is 25

C.T.E. is 14.4 × 10-6 /°C which is close to that of tooth

High thermal conductivity of 0.710cal/sec/cm2/(°C /cm)

Noblest of all metals

Mechanical properties affected by small amounts of impurities

Can be cold worked and welded at room temperature

Most efficiently sealing permanent fillings

5

BIOCOMPATIBILITY OF GOLD RESTORATIONS

A pure gold restoration is biologically sound

Pure gold is well tolerated by gingival tissue

Periodontal health of the tooth following placement of gold is questionable

Pulpal health following a direct gold restoration is questionable

Application of liners and bases is mandatory whenever recommended

With effective remaining dentin thickness of 3-3.5mm, use of cavity

varnish will suffice.

With effective remaining dentin thickness of 1-2mm, it is recommended to

use :-

A subbase of Zinc oxide eugenol followed by a cavity varnish and a base

of Zinc phosphate cement

A subbase of calcium hydroxide followed by a base of polycarboxylate

cement

• With an effective remaining dentin thickness of less than 1mm, there will

usually be destruction of pulp dentin organ.

6

TYPES

FOIL

o Sheets

o Pellets (hand rolled and commercially rolled)

o Cylinders (preformed and hand rolled)

o Ropes

o Corrugated foil

o Laminated foil

o Platinized foil

ELECTROLYTIC PRECIPITATED GOLD

o Mat gold

o Mat foil

o Gold calcium alloy

POWDERED GOLD

o Goldent

GOLD FOIL

7

o Gold foil sheets

Sheets are manufactured by a process called ‘gold beating’ or

‘rolling’

Pure metal is melted and formed into ingots of desired size

All light weight sheets are formed by beating. Heavier mallets are

used initially for beating gold ingots followed by lighter ones when

the gold gets thinner

Heavy weight sheets are formed by rolling. Gold is passed

continuously through the rolling mills until the desired thickness is

achieved

Gold foil sheets are bound in the form of books of 1/10 or 1/20

ounces

One book contains 12 sheets and each sheet commonly has the

dimensions of 4” ×4” .

No.4 gold foil is usually used which weighs 4 grains and is 0.51µms

thick

Varying numbers of gold foil sheets are available like

No.20,40,60,90 etc

8

Gold foil pellets

May be hand rolled or commercially produced

Pellet sizes may vary from 1/2 -1/128 which represent the portion of the

No.4 gold foil used to form a pellet

No.4 gold foil is removed along with its tissue paper from the book

Sizes ,which are commonly used for rolling into pellets are 1/16 onwards

The desired piece of gold foil is then grasped from the centre and held

between the thumb, index finger and middle finger of the left hand

Ends are tucked with tweezers towards the centre and rolled lightly into

round balls of loosely packed mass of gold

Pellets are degassed and stored in separate compartments of a gold box

Gold foil cylinders

This form can be both hand rolled and commercially rolled

It is custom made by rolling cut segments of No.4 gold foil usually1/2,1/4

and 1/8 into desired widths

Cylinders are degassed and stored in the gold foil box

9

Corrugated gold foil/Carbonized gold foil

Manufactured by placing thin sheets of paper in between the gold foil

sheets, which are then ignited

The paper burns and gets charred

The gold foil becomes corrugated

Platinized gold foil

This is a sandwich of gold and platinum with the platinum content being 15%

It can be formed in two ways :

1) One sheet of pure platinum foil is sandwiched between two sheets of gold

foil. These are then hammered until the thickness of one No.4 Gold foil is

obtained

2) Layers of platinum and gold are rolled over together so that there occurs

fusion of the two even before the beating procedure has begun

Platinum increases the hardness and wear resistance of the restoration

This form can be applied in stress concentration areas like incisal edges

and cusp tips

Laminated gold foil

A combination of 2-3 foils with crystals running in different directions

More resistant to the applied forces

10

COHESIVE AND NON-COHESIVE FORMS

Pure gold can be classified into cohesive and non-cohesive forms

Two gold surfaces can cohere by welding at room temperature only if the

surfaces are atomically clean

Manufacturer may supply to the dentist a gold foil which is essentially free

of any surface contaminants and can be directly placed into the cavity

preparation. Such a form of gold is called the ‘Cohesive gold’

It is recommended to degas even the cohesive forms before placing them in

the cavity preparation as some adsorption of gases like carbonic acid gas,

phosphoric acid gas, hydrogen sulphide gas etc. are likely to occur during

storage and transportation

‘Non-cohesive form of gold’ is one in which certain non-volatile

contaminants like iron,sulphur or phosphorous are permanently deposited

onto surface. They do not have sufficient strength and hardness compared

to their counterparts.

ELECTROLYTIC PRECIPITATED GOLD

Consists of crystalline gold powder formed by electrolytic precipitation

Powder is formed into different shapes by heating at a temperature well

below the melting point of gold

11

Diffusion of the particles occurs at the point of contact so that the particles

coalesce and grow

Mat gold/crystal gold

First referred by Rule in 1937 in his analysis of gold foil

This is electrolytically precipitated gold obtained by a process similar to

electroplating at an accelerated rate

Deposited material has a spongy structure with loosely arranged or fern

like crystals

During subsequent heating process, branch ends of the crystals are rounded

& tend to weld themselves together

Available in the form of strips of medium widths(2mm) and wide

widths(3mm),which can be cut to the size that fits the cavity

Mat gold being spongy in nature can be easily compacted and adapted to

the retentive portions of the prepared cavity

Its use is restricted to forming only the internal bulk of the restoration

Mat foil

Sandwich of mat gold placed in sheets of No.3/No.4 gold foil

Sandwich is sintered by heating to just below the melting point of gold and

cut into strips of different widths

12

Electralloy

An alloy of electrolytic gold and calcium

Calcium content is usually 0.1-0.5% by weight

Stronger restorations are produced by dispersion hardening

The product is sandwiched between two layers of gold foil for

convenience

POWDERED GOLD

Is in the form of minute particles

Can be obtained by atomization from a molten state or by chemical

precipitation

In chemical precipitation, gold is dissolved in aquaregia and precipitated

by Oxalic acid,sulphur dioxide or sodium nitrate

Average particle size is 15µms.

Powder is gathered into a conglomerate mass having a diameter of 1-3

mms

These masses are either sintered or lightly precondensed to facilitate slight

adhesion between the particles and easy handling.

13

POWDERED GOLD AND GOLD FOIL COMBINATION

This form was introduced in 1962 by Baum and Lund

Commercially available pellets of powdered gold wrapped in a gold foil

are known as ‘Goldent’

Powdered particles are mixed with a soft wax and held in a No.3 gold foil

Gold foil acts as a container for the powdered particles and facilitates their

condensation

Each pellet contains approximately ten times more gold than a pellet of

gold foil of comparable size

Ratio is 95% powder and 5% foil

Hand method of compaction is better than mechanical compaction for

powdered gold

ANNEALING/DEGASSING

‘Annealing’ a gold foil refers to the removal of surface contaminants

‘Degassing’ or ‘desorption’is the preferred term

Primary purpose is to produce an automatically clean surface and render

the material cohesive and workable

14

Degassing is done for non-cohesive gold to remove the protective ammonia

film placed deliberately on its surface by the manufacturer

Degassing for cohesive gold is done to remove various contaminants like

sulphur and phosphorous compounds, oxides or water vapour adsorbed on

its surface during storage and packaging

Temperatures in the range of 600-1300°F must be produced on the surface

on the surface of the gold to volatilize gases or other volatile contaminants.

Two methods can be used for degassing- the alcohol flame or the electric

annealer

HAZARDS FROM OVERHEATING DIRECT GOLD MATERIALS

• Possibility of recrystallization and grain growth

• Possible incorporation of impurities from the surrounding atmosphere in

the melting or just the very hot surface of gold when it is overheated, or the

adhesion of those impurities to the gold surface when it is energized by too

much heat for too long a time

• This hazard can occur in those gold materials that are supplied in sintered

form. Overheating during degassing can result in an oversintered situation

where the whole mass of particles will adhere to each other

• Complete melting of the gold surface which can make it completely non-

cohesive

15

• During mass contamination of direct gold, the pieces may tend to adhere

before inserting them in the preparation

Insufficient degassing creates pitting and porosity within final restoration due

to incomplete removal of protective gases making material only partially

cohesive

INDICATIONS

Incipient carious lesions

ClassІ lesions in premolar teeth and accessible development pits

Class I І lesions on premolar teeth

Class І І І lesions in maxillary and mandibular anterior teeth

Class V gingival lesions

• Erosion areas

• A typical lesions :

Proximal lesions on teeth adjacent to crown preparations

Vent holes in crowns and defective inlay/crown margins can be effectively

repaired with direct gold

Class VI lesions (cusp tips) and incisal edges

Retrograde root canal filling material

16

CONTRAINDICATIONS

Teeth with very large pulp chambers

Severely periodontally weakened teeth

Large carious lesions

Handicapped, elderly or young patients

Psychologically unsound patients

When economics is a limiting factor

Where esthetics is a prime requirement

Inaccessible/poorly accessible areas

Isolation unobtainable

Areas of undesirable occlusal stresses

Patients with a high caries index

Hypoplastic areas

17

ADVANTAGES

1. A permanent method for repairing teeth, and the restoration could

last as long as the tooth itself

2. Does not tarnish and corrode in the oral cavity

3. Insoluble and has a coefficient of thermal expansion close to that of

tooth

4. Atraumatic cavity preparation

5. No tooth discoloration around the margins

6. No cementing medium is necessary for retention of the restoration

7. Surface can be effectively polished and has long lasting smoothness

8. Pure gold is ductile and can be burnished to produce an accurate

margin for the restoration.

9. Can withstand compressive forces sufficiently

10. The restorative procedure develops skills of the operator in other

dental procedures also.

11. Most efficiently sealing permanent restorative material

18

DISADVANTAGES

1. Unesthetic

2. Expensive

3. Long chairside time required for restoration

4. Use limited to conservative cavities

5. High thermal conductivity could lead to postoperative sensitivity

6. Technique sensitive

7. High condensation forces may injure the tooth and supporting structures

CONDENSATION OF THE DIRECT FILLING GOLD

Condensation is the procedure used to condense and harden gold inside the

cavity preparation

Results in a dense porous gold restoration

Objectives of compaction :-

Cohere two pieces of gold to each other. This process is known as welding

Adapt the gold intimately to the walls and margins of the prepared cavity

Cold work and harden the gold mass to increase its strength

19

To drive away air from in between the pieces of gold and gold-tooth

interface

PRINCIPLES OF CONDENSATION

1) Force of the blow :-Average force required to condense gold with a

condenser point of 1mm diameter is 15 pounds

Delivering forces from a mallet are recommended

Factors which control the ultimate force delivered in a blow are :-

a. Weight of the hammer and the velocity with which it is brought

down on the condenser

b. Resistance of the substance receiving the blow

c. Area of the condenser point in contact with the restoration

2) Direction of the applied force during condensation is called as the line of

force

Force applied with a condenser parallels the long axis of the instrument

shaft

While compacting in the centre of the cavity, forces are usually directed at

90° to the pulpal floor.

3) Small condenser tips (0.5-1.0mm) are usually considered adequate to achieve

the desired compaction

20

4) Uniform stepping of the condenser point is important to ensure hardening and

welding of the entire restoration without leaving behind any voids.

STEPPING is the overlapping of the previous area of the condenser’s stroke

by half or one fourth both in individual steps and in lines of steps

Stepping process can proceed in two ways :-

a) Moving parallel to the wall and wedging the final row between the already

condensed mass of gold and cavity wall

b) Moving perpendicular to the wall. The final row wedges the gold between

that wall and the already condensed gold

5) Use the minimal thickness of pellet possible, provided that the condensers will

not penetrate it.

6) Energy of condensation :- It is more effective to utilize a lesser amount of

energy inside the cavity preparation and to increase energy of condensation

gradually as the step-by-step build –up proceeds to surface

Factors on which resistance to condensation energy depends:-

a) The more tone that there is in the periodontal ligament, the healthier the

periodontium will be , the more resistance there will be to the condensation

energy, and the more effective this energy will be in fulfilling the

objectives of condensation

b) The volume of the tooth being condensed against

21

c) The modulus of resilience

d) Design factors

e) Operator variables

f) Increment size

g) Technique variables

7) When inserting pieces of direct gold materials, condensation can be either

from one periphery of the increment to the other, or from the center of the

increment to the peripheries

8) Condensation of precipitated types of direct gold materials should be

started by hand. When the material is unyielding to the hand condenser,

mechanical condensation can proceed

METHODS OF APPLYING CONDENSATION FORCES

Condensers are instruments used to deliver the forces of compaction to the

underlying restorative material.

Several methods for application of these forces :-

a) Hand pressure- Small condenser points of 0.5mm in diameter are generally

recommended

b) Hand malleting- Long handled condensers and leather faced mallets(50

gms in weight) are used for this purpose

22

c) Automatic hand malleting- utilizes a spring loaded instrument that delivers

the desired force once the spiral spring is released

d) Electric malleting(McShirley electromallet)-Intensity generated can vary

from 0.2 ounces to 15 pounds and frequency can range from 360-3600

cycles/minute

e) Pneumatic malleting(Hollenback condenser)- consists of vibrating

condensers and detachable tips run by compressed air

23

Condenser instruments can be straight,curved,angled,round,square,or

rectangular

Surface of the tip can be smooth or serrated

The tip can be flat faced or convex-faced

Current condensers have a series of small pyramids or serrations on the

face

Plastic flow of gold occurs over short distances under the face of the

condenser

Densest structure occurs directly under the face of the condenser

Condenser should traverse the entire surface of each increment as nearly as

possible

COMPACTION TECHNIQUE

• Gold foil cut to the size and shape of the cavity is spread out in a smooth

concave form by hand

24

• Gold is adapted lightly to the cavity walls, line angles and point angles by

hand pressure

• Gold is held steady by a holding instrument, and a condenser of desirable

size is used to begin malleting in the centre of the mass

• Slowly, the condenser is moved to the periphery along straight lines using

the stepping process

• As it reaches the walls, the condenser is turned from 90°to 45°such that it

bisects the line angles and trisects the point angles

• While building the restoration, forces of condensation must be directed at

90°to the previously condensed gold

• Compaction of first layer produces a building shelf and a gold bank is

developed on to it

GENERAL STEPS FOR INSERTION OF DIRECT GOLD RESTORATION IN A CAVITY PREPARATION

A. Three step build-up for the restoration

1. “ Tie formation”

This involves connecting two opposing

point angles or starting points filled with

gold with a transverse bar of gold. This

forms the foundation for any restoration in

direct gold

25

2. “ Banking of walls”

This is accomplished by covering each wall from its floor or axial wall to

the cavosurface margin with the direct gold material

• A wall should be banked in such a way that will not obstruct tie formation

or banking of other walls in

the cavity preparation

• “ Banking” should be

performed simultaneously on

the surrounding walls of the preparation

3. Shoulder formation

Sometimes, to complete a

build-up, it is necessary to

connect two opposing walls

with the direct gold material

B. “Paving” of the restoration

• Every area of cavosurface margin portion should be individually covered

with excess cohesive gold foil

• A foot condenser is useful for this purpose

26

C. Surface hardening of the restoration

Highest condensation energy is used on the surface of the restoration in all

directions, so as to strain harden the surface gold and to fulfill the rest of the

condensation objectives at this critical area of the restoration

D. Burnishing

• Creates a solid gold sheet marginally and on the surface

• Should be done with proper instruments, moving from gold to tooth surface

• Enhances surface hardening

• Adapts the material more to the margins

• Eliminates surface and marginal voids

E. Margination

• Using sharp instruments(e.g., knives and files), moving from the gold

surface to the tooth surface, try to eliminate excess in small increments at a

time

• This process is done until it is possible to visualize the original outline of

the cavity preparation

F. Burnishing

• Closes marginal discrepancies

• Strain hardens the surface

27

G. Contouring

• Anatomy of restoration is made to coincide with that of the tooth

• Restoration is made compatible with the that of the

opposing,contacting,and occluding teeth

• Done with knives,files or finishing burs

H. Additional burnishing

I. Finishing and polishing

• Minimal finishing and polishing is required with a properly surface

hardened,marginated,and contoured restoration

• Some finishing may be done using precipitated chalk or tin oxide powder

on soft bristle brushes or rubber cups

J. Final burnishing

Done to ensure closure of marginal voids and other surface discrepancies

28

PHYSICAL PROPERTIES OF COMPACTED GOLD

29