GOLD FOIL: ITS SELECTION, CHARACTERISTICS, MANIPULATION AND INSERTION

By ERLING THOEN," D.D.S ., Iowa City, IowaProfessor of operative dentistry, University of Iowa, College of Dentistry.

Read before the Section on Operative Dentistry at the Seventy-Seventh Annual Midwinter Meeting of the Chicago Dental Society, February 19, 1941.

The detection of dental caries, the most prevalent of all diseases of the human body, demands immediate attention because the consequences of uninterrupted dental decay often lead to disturbing systemic conditions. Many members of the profession, as well as those of other professions concerned with the healing art, are constantly striving to determine methods of preventing dental diseases. Much has been accomplished through dietary and other measures, but there remains the all important necessity of proper attention to existing caries.

In making restorations in teeth, the dentist must keep in mind that he is in duty bound to render the best service possible under existing conditions. His efforts must not be devoted solely to the

removal of carious tooth substance and the filling of the cavity with the most conveniently manipulated material. He must seriously consider the preventive as well as the restorative phase of the operation, and exert every effort to meet the requirements of both. The interruption of caries, provision for resistance against the forces of mastication, prevention of recurrent decay, establishment of correct occlusion and contour and development of pleasing esthetic effects are all important. These accomplishments demand, among other things, the selection of appropriate restorative material.

When selecting a restorative material, the operator should consider the conditions which he is obliged to meet. He must keep in mind the fact that all materials have both desirable and undesirable characteristics, and that he is largely responsible for the selection of the material to be used in each case. Of course, he may occasionally be obliged to yield

to the wishes of the patient and refrain from the use of the material which he deems best.

Unfortunately, we do not have available any material for the making of permanent restorations which can be regarded as ideal. If such material were obtainable, it should possess the following characteristics

t. It should be perfectly adaptable to all parts of the cavity.

2. It should not be affected by the fluids of the mouth.

3. It should possess sufficient crushing resistance and edge strength.

4. Its resistance to attrition should correspond to that of the enamel.

5. Its color should harmonize with that of the enamel.

6. It should be a non-conductor of thermal impressions.

7. It should be so constituted that it would take and retain a satisfactory surface finish.

8. Its volume changes should correspond to those of the hard tissues of the teeth.

g. It should be easily tolerated by the hard tissues of the teeth and by the soft tissues of the mouth.

10. Its manipulation should be a comparatively simple procedure.

11. Its cost should not be prohibitive. Considering these properties collec

tively, it can be seen that we do not now have any material which can be regarded as completely satisfactory for all types of restorations. We do, however, have materials which lend themselves to the restoration of certain parts of the oral cavity which can be regarded as rather satisfactory for the particular types of restoration for which they are primarily intended.

Let us consider the characteristics of gold foil in relation to those of the ideal restorative material, in order to gain a better understanding of gold foil, an excellent material in many permanent restorations.

Gold is not affected by the fluids of the mouth. There is absolutely no tend

ency toward dissolution of this material by the saliva or any other fluid that is taken into the mouth. This property is necessary to all materials, since it is one of the principal factors in the permanency of a restoration.

Gold takes and retains a satisfactory surface finish, an essential to the maintenance of oral cleanliness and the prevention of recurrence of decay.

No unfavorable volume changes occur after gold foil restorations are completed. Neither shrinkage nor expansion to any appreciable degree can be tolerated in any restorative material.

Gold foil possesses the most desirable property of being perfectly adaptable in all parts of the cavity. This, together

Fig. 1.-Outline forms.

Fig. 2.-Resistance and retention forms.

with its freedom from volume change, makes for perfect sealing of the cavity. There will be no recurrence of decay in any cavity in which gold foil has been properly placed.

Gold foil restorations resist attrition in a generally satisfactory manner.

One of the important considerations with any material is edge strength and the ability to withstand the forces of mastication. Gold foil restorations afford sufficient edge strength, and offer sufficient resistance to the forces of mastication. No other material possesses these properties to a higher degree, with the possible exception of some of the alloys used in the construction of cast gold inlays.

The hard tissues of the teeth tolerate gold in any form. Pulp disturbances

under gold foil are no commoner than under other metallic materials.

The unfavorable properties of gold foil are few. Its color may not be particularly pleasing when in contrast with tooth tissue, but, in many cases, this can be corrected by special attention to the outline form of the cavity. A minimum degree of extension of cavity margins, consistent with prevention of recurrence of decay and convenience of insertion of the material, should be made. In addition, esthetic values can be assured by due consideration to the contour in finishing gold foil restorations.

The only other objectionable property of gold is its thermal conductivity. In foil, this objection is no greater than in

any other form of the material. Unfortunately, all metallic restorative materials are conductors of thermal impressions. This property can be minimized in many cases if unnecessary sacrifice of tooth substance is avoided, or it may be eliminated entirely in some instances through the use of intermediate substances such as cavity linings and cement bases. It might be well at this point to emphasize the advisability of encouraging patients to give early attention to incipient decay. Too often, patients are dismissed, after an examination, with instructions to return later for the treatment of initial decay. In addition to the usual discomfort accompanying preparation of cavities, the thermal changes naturally occurring in the mouth will

make for pain, in proportion to the depth of the decay and the size of the cavity. We occasionally hear members of the profession state that they do not use gold foil because of difficulty of manipulation. It seems unreasonable to offer such an excuse for not using this excellent material. It is true that the use of gold foil in a satisfactory manner requires observance of a rather exacting technic, but what other material do we have which does not require similar consideration for a completely satisfactory result? Certainly, no one would think of disregarding the specific instructions for the preparation and insertion of other materials if he thought that the end-result would

Fig. 3.-Forms of gold foil: sheets, ropes and manufactured pellets.

Fig. 4.-Annealing appliances.

be unsatisfactory. Let us disregard this so-called objection to gold foil and give attention to mastering the procedure involved in foil restorations. Gold foil deserves this consideration.

Gold foil is indicated in all classes of cavities. Owing to improved technics and the selection of other materials available, it may be said to be indicated in many pit and fissure restorations, proximal restorations of the anterior teeth and restorations of the gingival one-third of the labial, buccal and lingual surfaces. Because of certain advantages of the cast gold inlay over gold foil, the inlay may be given the preference in selected cases. The above-mentioned cavities can often be more quickly and easily filled with gold foil than with a cast gold inlay, and

the restoration will be more satisfactory. The time element is of importance in every operation, but of greater importance is a perfectly sealed cavity. Every operator appreciates the tendency to recurrence of decay around fillings, and he should attempt to prevent this by perfectly adapted restorations with the most dependable material. Gold foil serves well because of its extreme adaptability to cavity walls, angles and margins.

In selecting gold foil as the restorative material, the operator should take into consideration the following; (1) strength of the cavity walls; (2) condition of the supporting structures of the tooth; (3) accessibility of the cavity; (4) esthetic

requirements, and (5) physical condition and age of the patient.

The enamel walls of the cavity should be, as far as possible, supported by sound dentin. Since considerable force is necessary to proper insertion of gold foil, enamel should seldom be left unsupported. There are occasions when, for esthetic reasons, a part of a wall may be left unsupported by dentin. If the structure of the enamel is such that the gold beneath it will not be seen through the enamel, and if this enamel will not be subjected to the forces of mastication, dentin support may not be necessary. In such a case, the operator must exercise due precaution in applying force when condensing the gold in that part of the cavity.

The supporting structures of the tooth should be reasonably healthy, since pathologic conditions involving the peridental membrane may be aggravated by the force necessary to obtain condensation of the gold.

The accessibility of the cavity has been an important factor in determining whether gold foil is to be used. However, through the introduction of the pneumatic condenser, this factor can be eliminated in many cases.

Occasionally, gold foil operations are rather trying on the patient because of the necessity of maintaining quiet. Therefore, it is possible that the placing of gold foil should not be attempted in the

Fig.5.-Condensing instruments.

Line of Force

This

Not TMs

Fig.6.-Lineof force.

teeth of young people unless the disposition of the patient will permit the use of an exacting technic. Also, in young patients, the degree of root development should be taken into consideration. Teeth with completely developed roots are to be preferred because there is then no danger of disturbing the health of the tissues in the apical area in condensing the gold.

For aged and infirm patients, gold foil may be ruled out because of the life expectancy of the tooth. Nervous and excitable people may be difficult to handle, but usually, with tact and judgment in handling them, satisfactory gold foil restorations can be made without any detrimental effect.

The preparation of a satisfactory cavity for the reception of gold foil, and minimizing of the possible difficulties which might be encountered in making the restoration, requires, in some instances, the separating of the teeth. This may be accomplished by either the "slow method" or the "immediate method." Slow separation may be obtained by tying cotton cord around the contact point between the teeth, dismissing the patient for several hours, and depending on the saturation of the cord with saliva to bring about separation. Obtaining space in this manner is highly recommended because, in most

cases, it causes little soreness and there is little danger of injury to the supporting structures of the teeth. When separation is effected in this manner, the space is maintained by applying the mechanical separator before beginning the operation. If time will not permit separation by the slow method, immediate separation can be obtained with the mechanical separator, preceding the preparation of the cavity.

The use of the rubber dam for all gold foil operations is a necessity for better cavities, prepared with greater ease and more accuracy, and with less discomfort to the patient. Of course, its application is absolutely essential to introduction of the gold into the cavity. If gold

comes in contact with the saliva, the cohesive property of the material will be destroyed. The operator will be well rewarded for the time spent in applying the dam.

An understanding of cavity preparation is necessary to satisfactory gold foil restorations. The requirements for retention, preventing recurrence of decay and esthetic values will have to be considered. G. V. Black gave the profession its first practical system of cavity preparation. Compliance with this system will make for satisfactory cavities. With no attempt at a detailed discussion of

Fig. 7.-Outline forms for cavities.

Fig. 8.-Proximal aspect of prepared cavities

gold foil cavities, it might be well to briefly review the requirements for such cavities if the restorations are to be satisfactory.

Preceding every operation, the occlusion should be carefully examined. The relation of the tooth to be operated on to the adjacent teeth and its occlusion with the tooth, or teeth, in the opposite arch should be noted. This is important because the findings may influence the outline form o£ the cavity, and, in many cases, determine the cavity form in general.

The outline form of the cavity, which means the area of the tooth surface to be included within the enamel margins of the cavity, should, as far as possible,

be predetermined. (Fig. 1.) In all cases, it should be such that the margins will lie in immune areas; that is, areas that are habitually clean. These areas include the line angles of the crowns of the teeth, the apical two-thirds of the cusps, marginal ridges, the points of greatest convexity and areas incisally or occlusally from them, and under the so-called free margin of the gums. These areas are habitually clean because most of them are constantly swept by food, or they are cleansed by the movements of the tongue, cheeks and lips. Also, they are rather easily reached with the toothbrush. When considering the cavity out

line form for restorations which will probably be exposed to view, attention should be given to the esthetic requirements. It frequently happens that the latter consideration will prevent the exposure of so much gold as to be unsightly.

Resistance and retention form, wherein provision is made for absorption of the stresses of mastication and retention of the filling, must be correct. (Fig. 2.) Adherence to irregular box-forms seems advisable. Flat walls and definite angles, with dovetailing when necessary to prevent displacement, not only increase the resistance against the forces of mastication and the retention, but also minimize any difficulty in inserting the gold.

Convenience form includes such slight modifications in the form of the cavity as may be necessary to placing and condensing the gold, also cutting convenience angles in the surrounding walls of the cavity, which will serve as starting points for the gold. These angles should be definitely cut, of reasonable size and not too deep. They should be cut entirely within the dentin of the surrounding walls. The mistake should not be made of cutting these angles in the floor of the cavity whether this is the axial, pulpal or gingival wall, because, if so placed, they could not serve the purpose for which

Fig. 9.-Labial aspect of prepared cavities.

Fig. 10 -Labial aspect of tooth after separation has been obtained.

they are intended. It is a good rule to so place the convenience angles that they will oppose one another.

The enamel margin of the cavity should be beveled to remove short and loose enamel rods, which may break down during condensing of the gold, or fall out subsequently to completion of the restoration. A bevel of approximately one-fourth the thickness of the enamel on the surface of the tooth and a like distance on the wall of the cavity is usually sufficient.

Attempts to sterilize the cavity through the use of antiseptics or germicidal agents should not be necessary if the rubber dam has been applied during its

preparation. Black has stated that the most nearly sterile cavity walls are those which are freshly cut. It seems best to accept this statement and refrain from the use of sterilizing agents.

Absolute cleanliness is essential to the preparation and insertion of gold foil. Instruments used in handling and inserting the material should be thoroughly cleansed in advance of their use. It must be remembered that the cohesive property of the foil, when restored, is easily lost through the slightest contamination. The manufacturers of gold foil take every precaution to see that the gold reaches the dentist uncontaminated, and

that annealing is all that is required to make the gold cohesive.

Gold foil is obtainable in the form of sheets, ropes and uniformly prepared pellets, usually called cylinders. The number used in designating the sheets of foil, which are approximately 4 inches square, indicates the number of grains of gold per sheet. The most commonly used is No. 4. The sheets of gold are divided and rolled into ropes of uniform diameter each containing one-fourth, one-half or three-fourths of a sheet. The operator cuts the ropes into pellets of desired length. The so-called cylinders are really prepared pellets and their size is indicated by a number representing the

size of the rope from which they are made. (Fig. 3.)

Experienced gold foil operators have different preferences as to the form of gold. Some prefer pellets, which they themselves or their assistants prepare; others prefer the manufactured ropes, which they cut into pellets, and others prefer the manufactured pellets.

The operator prepares his own pellets by cutting the sheets of gold into pieces, each containing one-sixteenth, one-thirtysecond or one-sixty-fourth of a sheet, rolling the pieces with the fingers to form spherical masses of gold of the desired diameter. Pellets so prepared should not

Fig. 11.-Left: Labial and lingual convenience angles filled.   Center: Gingivo-axial angle filled. Right: Beginning filling of linguogingival angle.

be rolled too tightly because of the possibility of difficulty in developing the cold-welding property. Also, the use of too tightly rolled pellets interferes with the distribution of the gold during the building procedure.

For the operator who does not have an assistant whom he can train in preparation of the gold; or who, for other reasons, wishes to dispense with this part of the procedure, the pellets prepared by the manufacturer are very satisfactory.

Whether gold foil, asreceived from the manufacturer, is labeled cohesive or non-cohesive, it requires annealing to develop the cold-welding property when this is desired. While either cohesive or non-cohesive foil may be used for cer

tain restorations, the use of non-cohesive foil alone has been virtually abandoned. Because of its extreme softness, noncohesive foil may be used for a part of some restorations to insure adaptation of the material to cavity margins. Also, because of the possibility of introducing a considerable quantity of gold into the rather inaccessible part of some cavities in a comparatively short time, noncohesive foil in the form of cylinders can be used. (Fig. 4.)

The cold-welding property of gold foil may be developed by any one of three

methods. The foil may be subjected to the open flame; it may be placed on mica or porcelain and suspended above a clean gas or alcohol flame, or it may be heated with an electric annealer. The open flame method requires the use of a clean fuel, preferably grain alcohol, burning in a clean lamp. Most of the denatured alcohos are not satisfactory for this purpose because of the possibility of contamination of the gold by the denaturing agents. Three undesirable possibilities will have to be considered in annealing in this manner. First, there is the possibility of contamination of the gold as already mentioned; secondly, the gold may be overannealed, with resultant harshness, and the gold may even be

fused, and, thirdly, the gold may be underannealed, which would prevent development of the cold-welding property. However, experience with this method will eventually result in a satisfactory method.

Annealing gold on mica or porcelain over an open flame will be quite satisfactory, but the use of a dependable electric annealing appliance is superior because there will be no danger of contamination o£ the gold attributable to the appliance, and little danger of over. annealing if proper attention is given to

Fig. 12.-Left: Linguo-axial angle filled and gingival margin lapped. Center: Labiogingival margin lapped. Right: Lingual margin lapped, lingual line angle restored and incisal retention angle filled.

the time during which the gold is subjected to the heat.

In making any gold foil restoration, it is the expectation or intention of the operator to (1) secure the greatest possible density of the mass of gold in the cavity; (2) obtain the best possible adaptation of the material to all parts of the cavity, and (3) place in the cavity sufficient gold for correct contour when the restoration is complete.

The density of a mass of gold employed in a restoration may not equal that of the cast gold inlay because of the lack of one or more of the conditions necessary to attain such density. The density will be governed, first, by the character of the resistance to the force

Fig. 13. Left: Contact point restored. Center: Labial margin lapped. Right: Labial line angle restored.

used in condensing the material; secondly, by the area over which the force is expended, namely the size of the condenser points used, and, thirdly, by the kind and amount of force used in condensing.

Healthy tissues and strong cavity walls will, of course, tolerate more force than will diseased tissues and weak or unsupported walls. Therefore, the condition of the peridental membrane and the strength of the surrounding walls of the cavity are to be considered in determining the amount of force that can be safely applied.

Of considerable importance in attaining the desired density of gold is the size of the condenser points used. Black has emphasized this by stating that doubling the diameter of the face of the condenser point necessitates increasing the force four times, to obtain the same density. For this reason, then, it is advisable to use the smallest condenser points possible to be consistent with good operating and conservation of time in placing the filling.

Condensing force may be applied by the assistant while the operator manages the condenser point; or condensation may be obtained with the automatic mallet or with the pneumatic condenser. Black says,

Of the different plans for applying mallet force, the hand mallet used by the assistant is by far the best, as it will produce the desired results with the least wear and tear to both patient and operator. The next best, but much inferior method is by use of the automatic mallet.

The pneumatic condenser, which was recently introduced, is an excellent appliance and will serve in a very satisfactory manner for condensing gold foil. This instrument, because of its straight and angle handpieces, makes possible the placing of gold foil in many cavities which in the past have been regarded as

too inaccessible to permit operating in a satisfactory manner. Also, experience has shown that its use causes little discomfort to the patient, a factor to be considered in selecting gold foil as the restorative material. (Fig. 5.)

In any gold foil restoration, there is probably no part of the procedure of greater importance than the constant application of a correct line of force in condensing the gold. (Fig. 6.) The line of force means the direction in which the force is applied. Generally speaking, the force should be so directed as to drive the gold toward the line angles of the cavity rather than toward the individual walls. In other words, the force should

parallel an imaginary line bisecting the angle formed by the junction of the surrounding walls with one another and with the axial or pulpal wall. Of course, it may be necessary to apply the force directly toward an individual wall in some part of the procedure. The location and degree of exposure of the cavity influence, to some extent, the line of force, and they may be so related to the procedure as to require the application of the line of force directly toward some cavity wall. Without considering some specific type of restoration, it is rather difficult to give a detailed discussion of

the line of force. Emphasis has been placed on this consideration because only by its correct application can perfect adaptation of the material to the cavity be obtained.

Intimately associated with the application of the correct line of force are other considerations. Following the anchorage of the gold in the convenience angles, attention should be given to deposition of the gold for the main body of the restoration. The logical procedure is to immediately begin placing gold in the most inaccessible part of the cavity. This is advisable, since, otherwise, there may be interference with the filling of this part of the cavity later on. To disregard this suggestion only invites diffi

culty and dissatisfaction with the remaining part of the procedure and the final result.

The condensing procedure should be carried out in an orderly maner. With an appreciation of the extreme malleability of pure gold, we should, in some manner, try to use this characteristic to advantage, constantly beginning condensation of the pellets at or near their center or near the center of the mass of gold, and gradually working toward the periphery of the mass. In so doing, it is advisable to properly step the condenser point; that is, move the point approximately one-half its diameter for the suc

Fig. 14.-Labial aspect of restoration before polishing.

Fig. i5.-Labial aspect after polishing.

ceeding blows of the condensing appliance. This will insure that no uncondensed areas in the gold remain, resulting in the attainment of maximum density, and we shall have used the resiliency of the dentin to advantage in that the frictional resistance so created will prevent loss of the restoration, and, through perfect adaptation, the cavity will be perfectly sealed.

After the foregoing procedure, a concavity of the surface of the mass of gold will probably be developed. This is to be desired as it will mean that the margins of the gold will reach the beginning of the bevel of the cavosurface angle in advance of the main body of the gold and this, in turn, will make it possible to lap the margins of the cavity ahead of the body of the filling, thus helping to insure sealing of the cavity. If this is disregarded, it will be found, on completion of the restoration, that addition of gold to the margins will be necessary. It will soon become evident that this cannot be easily accomplished with satisfaction. The mistake should not be made of attempting to cover all margins of the cavity too far in advance of the main part of the restoration. Such a procedure would be illogical.

If the restoration involves a contact point, a special effort should be made to secure the best possible condensation in this area, to prevent too rapid wearing at this point. Again let me emphasize the advisability of securing separation of the teeth in making restorations wherein the contact is involved. The necessity for this can now be appreciated.

The necessity for careful attention to

contour in finishing gold foil restorations has been previously mentioned. It must be remembered that one of the principal objections to gold foil is its color. Also, it must be remembered that this objection can be minimized. Close observation of surface contour, including line angles, and necessary modifications of them will help to create a better impression of gold foil restorations. A high polish is not necessarily essential to gold foil restorations. In fact, they will, in many cases, be less conspicuous without a polish, but smooth surfaces are necessary to cleanliness and prevention of recurrent decay

Conclusion.

This presentation must not be regarded as so comprehensive as to require no additional study of gold foil as a permanent restorative material, if the operator expects to use this material with satisfaction. Experience is necessary to correct manipulative procedures. Realizing that this paper contains no new information about gold. foil, I have offered it with the expectation that it will help to stimulate the use of foil by those who, in the past, have neglected to give it the consideration which it deserves. Many discriminating members of our profession are using gold foil. They are sincerely trying to give their patients the best service of which they are capable. We should manifest our interest in and satisfaction with foil, not only by using it ourselves, but also by encouraging others in its use. Finally, let us urge our patients to accept gold foil when it is indicated, in place of other materials of a less permanent nature.