Direct filling gold/ dental implant courses by Indian dental academy

FLOW CHART: I II III IV

Introduction History General Considerations Types of Direct Filling Gold i Gold Foil -Sheets -Cohesive -Non-cohesive -Preformed -Laminated -Pellets -platinized ii Electrolytic precipitate -Mat Gold -Mat Foil -Alloyed iii powdered Gold

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Removal of Surface Impurities -Different Methods -Hazards of overheating and underheating Condensation or Compaction Metallurgical Consideration of Direct Gold Restoration Mechanical Considerations of Direct Gold Restoration Biological Consideration of Direct Gold Restoration Sealability of Direct Gold Restoration Indications of Direct Filling Gold Contra Indications Decline in Direct Gold Restorations Newer Introductions -Stopfgold -E-Z Gold Conclusion Referance

VI VII VIII IX X XI XII XIII XIV

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INTRODUCTION Since antiquity, pure gold has been a metal of special intrinsic and practical value. It would be redundant to review the importance that has been placed on this material by individuals and cultures of all ages. From the dawn of civilization until the present time, man has utilized gold in some form or other in practice of dentistry.

Very few metals are used in the pure state for dental restorative purposes, gold being the outstanding exception. One of the first materials used for dental restoration was “pure gold�, although the purity may be even higher in the gold used today. For direct filling, gold has fallen in popularity considerably from its high, but it is experiencing a resurgence of moderate proportions in North America, Sweden and Germany.

Direct filling gold are those gold restorative materials that are manufactured for compaction directly into prepared cavities. Several types are available and most of them are pure 24 karat gold.

Pure gold has been in use in dentistry in the United States for a well over 100 years. A variety of techniques has been advanced for its use in the restoration of teeth.

It is generally agreed that this noble metal is superior to all other restorative materials for treatment of many small lesions and defects in teeth, given sound pulpal and periodontal health. Success is achieved with direct gold restoration, if meticulous care is given to an exacting technique in cavity preparation, design and material care is given to an exacting technique in cavity preparation, design and material manipulation. Direct gold restorations can last for a life time it attention is paid to details of restorative technique in cavity preparation, design and material manipulation. Direct gold restorations can last for a life time if attention is paid to details of restorative technique and proper home care. The longevity of direct gold restorations is a result of both the superb bio-comparability of gold with the oral environment and its excellent marginal integrity.

HISTORY - Direct filling gold were done by Givovanni Arcolani almost 500 years ago.

- Gold foil for restoration purposes was introduced in America by Robert Woffendale in 1795.

- Sponge gold, a crystalline form, was introduced in to dentistry in 1853. This is made by amalgamating the gold with mercury and then driving off the mercury by heart.

- The discovery of its adhesive properties in 1855 us attributed to Robert Arthur.

- Corrugated gold is made by burning gold foli sheets between paper in the absence of air. This type was discovered in 1871.

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The long history of excellence and performance of the material prompted the establishment of a special academy- American Academy of Gold Foli operators. As gold has captured the fancy of civilized man throughout history, so has direct gold as a restorative material generated the respect and admiration of sophisticated and exacting operative dentists.

GENERAL CONSIDERATIONS Gold is the most noble of metals seldom tarnishing or corroding in the oral cavity. In this and certain other respects, it is an almost ideal dental restorative material for permanently preserving tooth structure. It’s chief disadvantages are its colour, high thermal conductivity and technical difficulties in forming a dense restoration.

The Brinell hardness of pure gold is about 25. This would seem to contraindicate its use as a restorative material. However its malleability and lack of surface oxide permit building a restoration directly in the cavity. In the process, the strength of the gold is increased by cold working. The lack of surface oxide with gold and few other metals cold welding, that is welding of increments together can be accomplished simply by pressure at mouth temperature rather than by melting, as in welding in other metals. The metallic bonding between the overlapped increments produces the direct gold restorations.

Pieces of gold are placed in the prepared cavities and are welded together by the pressure of suitable condensing instrument. This process is referred as condensation or compaction and the gold restoration is built up into a coherent mass by welding technique. The cohesion results from metallic bonding between overlapping increments.

The direct gold restoration is a demanding one. Because of the care and cleanliness required in handing the metal and the organization and skill necessary in its use, cohesive gold has acquired a reputation as a material that embodies perfection in the hands of a skilful, well trained operative dentist. It is impossible to achieve acceptable results using careless or sloppy techniques.

The lesion to be restored must not be subject to heavy chewing or biting forces. The use of gold is contraindicated for corners of teeth subjected to heavy msticatory stresses. The cavity must not be excessively large because more time and effort is required to place gold than composite or silver amalgam restorations. Large restorations therefore can be tiring for both operator and patient.

Chalky or mottled enamel could contraindicate the use of gold. Finishing the gold at the marginal area requires forces on the enamel, which could pulverize the surface it is not a glassy or pearly white texture. The lesion and site of operation must be accessible, as good visibility and operational access are important with this material. Last but least, display of gold in a smile could be a deterring factor when used in certain locations in the anterior teeth and maxillary premolars.

Notwithstanding these contraindications, direct gold has its value in all kinds of cavities and in many places within the mouth. It can be used to restore class I, II, III, IV and V lesions as well as to repair holes in crowns and restore abraded cusps.

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Common sense and judgement, tempered by experience will guide the conscientious operator in the proper use of the material.

Gold process a number of important characteristics which render it of special value as a restoration material. These characteristics may be summarized as follows.

1.

Cohesiveness, to a greater extent than any other metal. This quality depends largely on purity. The best gold’s for restoration purposes are about 99 parts in 1,000 pure gold.

2.

Softness during manipulation. This quality depends largely on purity.

3.

Malleability. It exceeds all other metals in this respect. It may be reduced by beating to 1,250,000 of an inch in thickness. Reamer is stated to have produced a sheet 0.00000087 inch thick.

4.

Ductility. It is the most ductile of all metals. One grain pure gold may be drawn into wire nearly 300 feet long. ii) Electrolytic precipitate a – Mat b – Mat foil c- Alloyed iii) Powder Of these the platinized foil and alloyed electrolytic precipitate are the two exceptions which does not have 99.9% purity.

1. Gold Foil Historically, gold foil is the oldest of all the products described. It has been used for many hundreds or even thousands of years. Because gold is so malleable, it can be reduced in thickness almost to transparency. Gold foil is manufactured by beating pure gold in to thin sheets. It is reduced by rolling to 25 µm (0.001”) or less.

For dental use, 25µm is the starting point for a beating operation that reduces it to submicron thickness. The surface texture of the foil is a replication of the surface against which the foil is formed.

The gold foil is cut into 4 x 4 inch (10 x 10cm) sheets and sold in books of sheets separated by thin papers. The books contain 1/10 or 1/20 that weigh 4 grains (0.259 grams) and are about 0.51µm thick. The numbering system refers to the weight of the sheet, so it reflects the thickness as well. Thus No:3 foil is used in the electrolytic and powdered products No:2 foil weighs 2 grains.

MANUFACTURE OF GOLD FOIL The process of manufacture of gold for restoration purposes is interesting. The foils are made from pure metal by the processes of beating and rolling; all light-weight foils are produced by beating and heavy foils by rolling. Absolute purity is essential in the manufacture of foils.

The bullion (pure metal) is first melted and poured into ingots of suitable size; these are the rolled by machinery into thin ribbons about one inch wide and a little thicker than ordinary papers. The thickness is regulated by the weight of the foil to be produced. The ribbons are now cut into 1-inch squares, each weighing 3,4,6 or 10 grains, etc., depending on the weight of the foil desired.

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These squares (!-inch) are then laid between sheets of goldbeater’s skins made from intestines of bullocks, or of vellum paper. These skins or vellum papers are cut into 5inch squares, and many of these are piled one upon the other, with squares of rolled gold interposed. The pile is now wrapped in heavy parchment, and so bound that all the edges are well protected.

The wrapped package is then placed upon a heavy polished stone block, approximately 3 feet high by 15 inches square, the block resting upon a foundation which is set in the ground 3 or 4 feet to give it solidity. With a large, round-faced mallet, the package is then beaten with heavy blows, being turned slightly after each stroke of the mallet. The time consumed in the beating process usually is from 2 to 3 hours.

After the foil has been beaten to the desired thinness, the leaves are removed, trimmed, and placed in paper books, ready for dispensing. Rolled gold is made by passing it through specially prepared rolling mills until the thickness required is obtained. All foils, after beating or rolling, are noncohesive. The cohensive property is developed by a process of slow beating or annealing.

Marcus Bull, in the goldbeating business in Hartford, Conn., was according to available records, the first to prepared gold especially for dental use. He shares this honour with his apprentice, alter his partner a Mr.J.T.Abbey. The old-time goldbeater received his pay by being allowed all the metal which was beaten outside of the mold.

A) SHEETS- COHESIVE AND NONCOHESIVE : Although all forms of direct filling fold could be supplied in both the cohesive and the non cohesive condition, in practice only the sheet foil is furnished in both conditions. As previously noted, the ability of gold to cohere by welding at oral temperature is dependent on a clear surface.

Gold, like most metals, attracts gases to its surface and any absorbed film prevents the intimate contact required for cold welding. For this reason, the manufacturer usually supplies the foil to the dentist essentially free of surface contaminants and , therefore, inherently cohesive. Although some absorption of gases may occur during storage, this type is referred to as cohesive foil.

In contrast, the manufacture may subject the foil to a volatile agent, such as ammonia, which is absorbed on the surface of god. This substances acts as a protective film to prevent absorption of other less volatile substances and premature cohesion. The ammonia treated foil is called non-cohesive foil. The non-volatile film is readily removed by heating to restore the cohesive character of the foil. Truly non cohesive foils, which have a permanent film, are not available now.

B) Preformed foils – Ropes, Cylinders, Laminated and Pellets : Because the 4 x 4 inch sheets of foils are too large to use in restorative procedures, they are rolled into ropes, cylinders or pellets before insertion into cavity preparations.

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Although some practitioners have historically made their own ropes, cylinders and laminates, now ropes and cylinders are available in preformed shapes. Both are made from No.4 foil that has been “carbonize” or “corrugated”. This form of gold foil is of historical interest because it was an out come of the great Chicago fire in 1871.

A dental dealer had some books of gold foils in a safe. After the fire, it was found that the paper between the sheets of foil had charred. However, the gold foil was unharmed, expect that it had become “corrugated” because of the shrivelling of the paper during carbonizing in the air tight safe.

Pellets of gold foil are generally rolled form 1/32, 1/48, 1/64, 1/128 sections cut form a No. 4, Sheet of foil. The book of foil is marked and cut into squares or rectangles. Each piece is placed on clean finger tips, and the corners are tucked into the center; then it is lightly rolled into pellet form.

The ropes and cylinders are rolled in various diameter and then cut to various lengths to provide many sizes of increments for filling the preparation. Pre rolled cylinders may be obtained in No. 4 or the thinner No. 2 gold foil, which is termed “Extra – Ply”, and may be purchased in 1/10 – or 1/20 ounce vials.

The laminates are not available as performs but may be made by the dentist by placing number of sheets on top of each other, then cutting the laminate into pieces of desired size.

C) Platinized Foil This might be considered as a laminated foil in which pure platinum foil is sandwiched between two sheets of pure gold foil. The older product was made by bonding the layers of platinum and gold together by a “cladding” process during the rolling operation. Thus the “sandwich” is already welded together before the beating.

This produce is available only in No. 4, sheet form. The object of adding platinum of the gold foil is to increase the hardness of the restoration. This material creates a restoration surface that is harder than conventional gold foil after compaction and it is used for restoration of tooth surfaces subject to heavy occlusal wear such as the tips of cusps of posterior teeth.

II) ELECTROLYTIC PRECIPITATION Another form of gold for direct filling is crystalline gold powder formed by electrolytic precipitation. It cannot be described as a foil because it is not formed by mechanical thickens reduction. The powder is formed in to shapes by sintering.

Sintering causes self diffusion between particles where they are in contact, so the crystals actually grow together. This process takes place at temperature much below the melting point of gold.

A) MAT GOLD (Strips) Mat gold is crystalline, electrolytically precipitated gold formed into strips.

These strips are cut by the dentist into desired size. The commonly available strips are either medium (2mm) or wide (3mm) widths. It is often preferred for its ease in building up the internal bulk of the restoration because it can be more easily compacted into, and adapted to, the retentive portions of the prepared cavity.

However, foil is generally recommended for the external surface of the restoration. In 6

other words, the mat is covered with a veneer of foil. The crystalline form of the mat powder with its large surface area does not permit easy welding into a solid mass gold foil. Therefore there is a greater tendency for voids that may show up as pits if it is used on the surface of the restoration B) Mat Foil Mat foil is a sandwich of electrolytic precipitated gold powder between sheets of No.3 gold foil. The sandwich is sintered and cut into strips of differing widths. The dentist can cut these to the desired length. The purposed of sandwiching mat between foil sheets was to try to eliminate the need to veneer the restoration with a layer of foil.

This type is no longer marketed.

C) Alloyed Electrolytic Precipitate The newest form of electrolytic precipitate is alloyed with calcium. It is called Electralloy R.V. The calcium content of the finished product is about 0.1%. Its purpose is to produce stronger restorations by dispersion strengthening. This locks in cold work strengthening. It is available in strips and cut to desired length before insertion into a cavity preparation.

III) POWDER GOLD Since at least the middle of the 19 th Century, chemically precipitated gold powders have been available in agglomerated form. These agglomerates usually disintegrated when compaction was attempted. The first successful use of powder gold started in early 1960’s when the gold powder was enclosed in No. 3 gold foil.

“Goldent” is powdered gold made by a combination of chemical precipitation and atomizatio0n. The maximum particle size is about 74µm(atomized), and the average is about 15µm. The atomized and chemical precipitated powders are first mixed with a soft wax in order to form pellets. These wax gold pellets are wrapped in No.2 ½ or No. 3 foil. The resulting pellets are cylindrical in shape and are available in several diameters and lengths. Each pellet of Goldent contain approximately 10 times more gold than a pellet of gold foil of comparable size. Prior to its condensation the matrix is burned away leaving only pure gold to be packed in to the cavity.

E-Z Gold is a recent product similar to the older goldent. It’s produced by Williams Gold refining Co. Newyork. It has improved working properties.

REMOVAL OF SURVFACE IMPURITIES (ANNEALING / DEGASSING / DECONTAMINATING / HEAT TREATMENT / DESORBING) 900-1300O F. The primary reason that direct gold materials are so convenient for building restorations is t hat they can have complete cohesion of space lattices at room temperature by simply bringing two pieces together and applying pressure to facilitate the cohesion process. It is only necessary to remove any contaminants from gold surface. So that it is possible to create more proximity between the gold pieces.

During manufacturing and packaging, these products are never handled manually, and there are various heating stages that remove gaseous surface contamination. However, during storage and packaging they are exposed to the atmosphere. Since gas can absorb on the surface of the gold, it is necessary for the dentist or dental assistant to 7

heat the foil or pellet immediately before it is carried to the prepared cavity. This step is commonly called annealing or heat treatment or desorbing or decontaminating or degassing. This application of some thermal energy can introduce molecular motion in those contaminants, vaporizing them off the surface. Thus the two main objectives of the decontamination process are i) to drive impurities of the surface, thus making the surface ready for cohesion and ii) to keep this surface devoid of any other impurities until complete cohesion occurs during building of the restoration. A certain amount of recrystallization stress relief also may occur with this process although neither of these is the objective of heating. Rather, the gold is heated as a precautionary measure to remove any surface gases and to ensure a clean surface.

Desorbing or degassing is essentially needed. Even in the container, air (oxygen and nitrogen) is present. When the gold is not in the container, either is storage at the manufacturer’s plant or in the dental office, other gases are possible contaminants. Eg. Moisture, sulphur dioxide, ammonia. If the dentist or assistant forms foil, Chamois finger tips should be worn to protect the gold from contamination. A totally dry cavity is mandatory throughout the compaction process.

Process desorption is a matter of heating long enough at a temperature that will remove gases and in case of powder gold, burn away the wax. In an attempt to determine the optimal temperature for removal of surface impurities, specimens were uniformly compacted from gold foil that had been heated for 5mts at various temperatures. The data indicated that temperature below 315OC (600OF) are not adequate to attain optimal hardness of the compacted gold. The values were not significantly different in the temperature range between 315OC (600 O F) and 760 OC (1400 O F). Reversible gases (oxygen and ammonia) can be readily removed by heat in the range of 900 O F to 1300 O F. Degassing can be accomplished in one of the three ways 1. By an open alcohol flame : The method of flame desorption consists of picking up each piece individually, heating it directly in the open flame and placing it in prepared cavity. The fuel for the flame may be alcohol or gas, but alcohol is preferred, as there is less chance of contamination. The alcohol should be pure methanol or ethanol without colorants or other additives. With this method it is important to use the middle zone of the flame or the high energy reducing zone (Blue Zone). Each piece of gold is held in such a zone for three to five seconds before inserting into the cavity preparation.

Advantages of using flame desorption include the ability to select a piece of appropriate size, desorption of only those pieces used, and less exposure to contamination.

2. Mica over a flame : A sheet of mica can be used over any type of flame, and is used somewhat as a heating element. Divide the surface of the mica into several areas to indicate the time the pieces of gold were put on the mica.

Maximally, five minutes are allowed for any piece of gold to be heated on mica. Care should be taken to handle pieces with stainless steel wire points or similar instruments that will not contaminate gold.

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3.

Electric Degassing : This is the most controlled and stadardized way of decontaminating gold materials. With this instrument, the heating compartment is made of aluminium. An electric heater controls the time and the temperature. The surface of the heater is divided into small compartments, each accommodating a piece of direct gold. This eliminated the possibility of cohesion of the pieces before they are inserted into the cavity Preparation.

Maximally, five minutes are allowed for any piece to be kept in the electric decontaminator.

Any of the three degassing procedures is satisfactory for all golds except Goldent (powdered gold). The goldent pellet is heated in the ethanol flame until a bright flame occurs caused by ignition of the wax and the pellet becomes dull red, then it is immediately withdrawn.

There are certain Hazards from overheating of the direct gold materials 1.

The first hazard is the possibility of recrystallization and grain growth. If this occurs, the mechanixal properties of the material will drop substantially. Recrystallization and grain growth are always functions of time and temperature therefore minimal time and temperature should be used.

2.

The second hazard will be the 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 a long time. Precautions should be taken to avoid degassing the gold in a polluted atmosphere.

3.

The third hazard can occur in those gold materials that are supplied in the sintered form. Overheating during degassing can create an over sintered form. Overheating during degassing can create an over sintered situation, so that instead of only surface atoms adhering to each other, the whole mass of particles will adhere each other. This situation can interfere with plasticity of the material when it is inserted into the cavity preparation.

4.

The fourth hazard is the complete melting of the surface of the gold making it completely non 窶田ohesive.

5.

The fifth hazard, especially during mass decontamination of direct gold, is that the pieces may tend to adhere before inserting in the preparation. This is especially likely to happen if they are on mica without being sufficiently spaced from each other, and may lead to larger pieces which are difficult to condense properly.

Under heating should avoid because it does not adequately remove the impurities, the result will be incomplete cohesion due to remaining impurities, or due to carbon deposited by the flame. This partial cohesiveness will create pitting and porosity within the final restoration.

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CONDENSATION OR COMPACTION: All direct filling gold must be compacted during insertion into cavity preparations. With the exception of Golden the compaction takes the form of malleting forces, which are delivered either by a hand mallet used by the assistant or by an Electro- Maller or Pneumatic Mallet used by the dentist. a) Objectives:The following are the main objectives for the condensation of direct gold material. i) Wedge initial pieces between dentinal walls, especially at starting points.

This is the first and most important step in building a direct gold restoration, for as soon as these pieces are positioned, it is to build the restoration over them. ii) Weld the gold pieces together by complete cohesion of their space lattices. iii) Try to avoid in general and to eliminate them from critical areas like margins and surfaces. iv) Strain hardening of gold materials which is due to the cold working during condensation. v) To adapt gold materials in to the cavity walls and floors. vi) Elastically deform the dentin of cavity walls and floors.

B) Modes of Condensation:  Hand instrument condensation  Pneumatic condensation  Electronic condensation  Hand condensation and Mallet C) Gold Condensation:  They are provided in different shapes  Round condensors  Parallelogram condensors  Foot condensers METALLURGICAL CONSIDERATIONS : A) Metallurgical Consideration of Cohesive Gold Foil A cross section of properly condensed cohesive gold foil will demonstrate the following features in the metallurgical microscope. i) The superficial 400 to 600 microns are formed almost completely of solid gold, with no voids. This layer is mainly due to burnishing. ii) The deeps 200 microns, in contact with a floor also are composed of solid pure gold with minimal voids. This is due to restraint nature of the walls against which gold has been condensed. iii) Serrated portions exist in the bulk of the restoration, with isolated areas of solid gold ranging and to 4 microns in thickness corresponding to the serrated condenser faces. These are areas of minimally sized voids. iv) The remainder of the restoration is full of voids, varying in size and number from one location to another.

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B) Metallurgical considerations of Mast gold restoration: In a microscopically viewed cross- section of a mat gold restoration, the following features are apparent. There will be no areas of solid gold i. e. voids will be spread throughout the restoration, even at the surface. Only strips of solid gold can be found within the restoration, which are actually the gold foil portion of the mat foil.

C) Metallurgical Consideations powdered Gold: When viewed microscopically in cross section powdered gold restorations, will be full of voids. Only scattered, thin areas of solid gold will be found within the restoration, corresponding to gold foil encapsulating sheets.

Therefore both mat gold and powdered gold should be veneered with cohesive gold foil, in order to establish a solid gold coverage on the surface and at margins of the restorations Metallurgical considerations diagrammatic representation MECHANICAL CONSIDERATIONS The mechanical properties of different direct gold restorations are the following A) Pure cohesive gold foil restorations will be the strongest, the densest, the hardest of all types. This is due to the greater cohesion between the ingredient foils in the completed cohesive gold restorations. They have fewer avoids, fewer foreign bodies and less number of component ingredients.

B) The smaller the size of the increments during condensation, the stronger will be the final restoration.

C) The greater the resistance to condensation, the harder and stronger will be the restoration.

D) The smaller the size of condenser, the better will be the resulting mechanical properties of the restoration – due to the high energy dissipated by smaller condensers.

BILOGIC CONSIDERATION IN DIRECT GOLD RESTORATIONS: The direct gold restorations can be some times irritant to pulp dentin organ.

The causes are i) the energy of condensation, not absorbed by restorative material, is dissipated to vital dental tissues creating deformities which may lead to irritation of pulp. The condensation forces should be always at a 45 0 angle to axial walls and pulpal floors, to avoid this. ii) The thermal energy in the gold pellet exceeding that necessary for decontamination will be mansmitted to dentin-pulp organ. iii) The frictional heat of finishing and polishing.

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iv)

Galvanic current established between catholic gold and other metal restorative materials.

The effect of direct gold restoration on the pulp- dentin varies with effective depths. i) with an effective depth of 3to 31/2 mm, a normal pulp will undergo healthy reparative action. ii) With an effective depth between 1to 2 mm, there will be an unhealthy reparative reaction. iii) With an effective depth less than 1mm there will be usually destruction of pulp dentin organ.

The need for protective bases also varies according to the effective depth. i) With an effective depth equal or more than 3mm, no intermidiatory base protection is necessary. ii) With an effective depth of 2mm or more, cavity varnish should be applied on all walls and floors expect on the cavo surface margins. iii) If the effective depths is 1 to 2 mm, a subbase of Calcium hydroxide or unmodified Zinc Oxide Eugenol is indicated. This subbase should be covered by varnish and then a base of Zinc phosphate cement. iv) With an effective depths less than 1mm, direct gold restoration are contraindicated.

SEALABILITY OF DIRECT GOLD RESTORATION Direct gold restorations are the most efficiently sealing permanent restorative materials. Not only does the microleakage space around these restorations have least dimensions, but the leakage space decreases with time. The method of condensation creating elastic deformation of the underlying and surrounding dentin, the nobility of the gold materials, the strengths of strained gold material, especially in very thin cross sections, and the complete insolubility of the materials in the oral fluids all contribute to this property.

INDICATIONS OF DIRECT FILLING GOLD • The direct gold restorations are primarily indicated for • Lesion with very limited dimensions and extent • Lesions in which cavity margins can be located on sound enamel surfaces.

• Lesions in vital teeth, having a sound pulp-dentin organ, intact supporting periodontium and the ability to withstand condensation forces.

• Lesions in which tooth structure left after removal of diseased tissue is bulky enough to create self resisting walls pronounced retention modes.

• Lesions in patients with good oral hygiene, low caries and plaque indices.

• Areas necessary to repair perforations in cast gold alloy restoration.

• Teeth with no enamel crazing or micro cracks.

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Specific Applications 1. Class I Direct gold restorations indicated in treatment of small carious lesions in pits and fissures of most posterior teeth and lingual surfaces of anterior teeth.

2. For small 3. Class III restorations on proximal surfaces of anterior teeth where lesions are small enough to be treated with pleasing esthetic results.

4. Class II restorations indicated for restoration of small cavitated proximal surface carious lesions in posterior teeth where marginal ridges are not subjected to heavy occlusal forces.

5. Incisal edges of cusp tips suitable for class VI direct gold restorations.

6. Margin of otherwise acceptable cast gold restoration can be restored with direct gold.

7. Used as a retrograde filling material after apicectomy.

CONTRA INDICATIONS OF DIRECT FILLING GOLD Direct gold restorations are contraindicated in some teeth with very large pulp chambers, in severely periodontally weakened teeth with questionable prognosis, when economic is a limiting factor and in handcapped, elderely or very young patients who are unable to sit for the longer dental appointment required. Root canal filled teeth are generally not restored with direct filling gold although they are the material of choice to fill the access preparation in cast gold crowns.

DECLINE IN DIRECT GOLD RESTORATIONS It was estimated that approximately one lakh nine thousand kilogram of gold were used in dentistry per year prior to 1970. This was roughly 7% of the total gold consumed per year in all fields then. But, with the spiralling price of gold in the early seventies, the usage of gold in dentistry diminished. The price of gold increased ten fold and remains at that level with minimal periodical fluctuations. Such steep increase has been the beginning of the decline of gold restoration in dentistry. Let us examine the various factors contributed to downfall of gold restorations.

A) 1.

2.

Factors connected with patient : High Cost : The cost of the treatment plays an important role in selecting the material for treatment. Cheaper materials were preferred by the patients.

Comfort : The prolonged period for which the mouth is to be kept open with rubber dam in position of a direct filling gold restoration might be too tiring for the patient. Another factor is the apprehension of the patient to open flame degassing on the chair side.

3.

4.

Necessity of extra visits : In case of cost gold restoration Aesthetics : Gold with its powerful yellowish hue was a symbol of richness in earlier days but presently people prefers a restoration which merges with the surroundings.

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5.

6.

7.

Galvanic Pain : A patient who has heard about or experienced galvanic pain will try to avoid it.

Allergy : Although extremely rare, it can occur Fear about personal safety : There were reported incidence where tooth with gold restoration were plucked by thieves and enemies.

B) Factors related with operations 1. Necessity of higher skills : For direct filling gold restorations more patients, greater stamina and better skill of the operator are needed. Lack of training in handling direct gold fillings in Dental colleges could be cited as the sole reason for not acquiring the required skill.

2. Lure of cosmetic dentistry : Most dental surgeons prefer to do restoration that blend with natural tooth structure. The advantages of restoration that blend with natural tooth structure. The advantages of gold restoration are not highlighted by the dental surgeons atleast in situations favouring it and because of its colour, gold is rejected.

3. Need for more chair side time : 4. Possible pulpal and periodontal damage : Careless use of condenser tips while doing a direct filling gold, may break the enamel margin.

5. Need for extra care during degassing : Underheating will not remove all the contaminants and there will be incomplete conhesion. Overheating can lead to over sintering and gold will become brittle and will not cohere.

C) 1.

2.

3.

4.

5.

6.

7.

8.

9.

Factors Connected with the Material.

Economy Non availability of instruments and equipments Lack of indigenous manufacture of dental gold High thermal conductivity – the thermal conductivity of gold restorations is approximately 400 times that of natural tooth.

Possible galvanic effect.

Softness of pure gold.

Higher density of gold alloys. The density of gold is 19.3 gms/cc. Which is double of chrome-cobalt alloys. This means, for a given volume of restoration, not only the base metal alloy will be cheaper, but also higher and hence more comfortable to patient.

Colour of gold Evolution of newer materials.

NEWER INTRODUCTION OF DIRECT FILLING GOLD To enthuse young dental surgeons into using direct filling gold restorations, newer materials and easier condensation t echnique are developed. The introduction of E-Z gold and stopfgold are the steps in that direction.

STOPFGOLD : 14

In 1989 a new granular type of direct gold, Stopgold was introduced in Germany and latter in U.S.A. by Degussa Corporation that morphologically differs from previously available directly filling gold. It is similar to Electroaloy RV in its properties and handling characters except that it offers an increase in shear strength 250%. When compared to gold foil.

According to manufactures, this new type of filling gold is produced from chemically precipitated gold powder (minimum gold content of 99.8%) that underwent a milling processing after precipitation. The individual particles are then loosely sintered together and cut into strips of 3.0mm wide and 40.0mm in length. It is available in three thickness. 0.7mm, 1.0mm and 1.5mm. Electron microscopically the material consists of flat polygonal platelets with a diameter of 25 to 75 microns and thyickness of 1.5µm. Hand condensation produced clinically satisfactory restoration and is easier to condense.

The 50% increase in shear strength of this material compared to conventional gold foil, is related to the high deformation that occurs during condensation, which improves cold welding ability.

The disadvantages of Stopfgold is said to be its cost that is 75% more than other form of granular gold. But still it is claimed to cost approximately only about Rs.600/- for an average sized class V cavity.

E-Z Gold : E – Z Gold is a new direct filling gold material that is similar to existing powdered gold formulations but more user friendly. It is a mixture of pure gold powder and wax (less than 0.01% organic wax), wrapped in gold foil introduced to the dental profession by Lloyd Baven in the late 1980’s. It’s imilar metallurgically to gold foil and powdered gold, in that when properly and thoroughly compacted, it has comparable properties, biocompatibility and performance. E-Z Gold’s manipulative characteristics are similar to that of a very stiff amalgam, yet more cohesive than gold foil. Manipulation of the material is claimed to be easy CONCLUSION Although direct filling gold is no longer the dentist’s first choice for most restorations, it still has a place in today’s ever growing selection of restorative materials. Knowing how and when to use direct filling golds can be an invaluable service to patients and subsequently a significant practice builder.

Introduction of newer verities like E-Z gold and stopfgold had made direct filling gold restorations easier to place. This improved manageability has made the restoration placement less time consuming and more predictable.

By incorporating direct filling gold in to a practice, dentists can offer their patients a restoration with greater expected longevity and better tissue response then either amalgam or composite and provide optimum restorative care.

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