At the World's Columbian Dental Congress, held in Chicago, August, 1893, the author presented an essay on "Tin Foil for Filling Teeth."

During the discussion of the subject, the following opinions were elicited:

Dr. E. T. Darby: "I have always said that tin was one of the best filling-materials we have, and believe more teeth could be saved with it than with gold. I have restored a whole crown with tin, in order to show its cohesive properties; the essayist has paid a very high and worthy tribute to tin."

Dr. R. R. Freeman: "I have used tin foil for twenty-five years, and know that it has therapeutic properties, and is one of the best filling-materials, not excepting gold."

Madam Tiburtius-Hirschfield: "I heartily indorse the use of tin, and have tested its cohesive properties by building up crowns."

Dr. A. H. Brockway: "I am a strong believer in the use of tin, on account of its adaptability, and the facility with which saving fillings can be made with it."

Dr. Gordon White: "After having used tin for nine years, I claim that it is the best filling-material that has been given to our profession."

Dr. C. S. Stockton: "Tin is one of the best materials for saving teeth, and we should use it more than we do."

Dr. James Truman: "I use tin strictly upon the cohesive principle, and would place it in all teeth except the anterior ones, but would not hesitate to fill these when of a chalky character."

Dr. Corydon Palmer: "For fifty-four years I have been a firm advocate of the use of tin, and I have a filling in one of my teeth which is forty years old."

Dr. William Jarvie: "I rarely fill a cavity with gold for children under twelve years of age that I want to keep permanently, but use tin, and in five or ten years, more or less, it wears out. Still, it can easily be renewed, or if all the tin is removed we find the dentin hard and firm. The dentist is not always doing the best for his patients if he does not practice in this way."

Dr. C. E. Francis: "I have proved positively that tin foil in good condition is cohesive, and my views have been corroborated by dentists and chemists."

Dr. James E. Garretson: "Tin foil is cohesive, and can be used the same as gold foil, and to an extent answers the same purpose."

Dr. C. R. Butler: "Tin is cohesive and makes a first-class saving filling."

Dr. W. C. Barrett: "Tin is as cohesive as gold, and if everything was blotted out of existence with which teeth could be filled, except tin, more teeth would be saved."

Dr. L. D. Shepard: "Tin possesses some antiseptic properties for the preservation of teeth that gold does not."

Dr. W. D. Miller: "I use tin foil in cylinders, strips, and ropes, on the non-cohesive plan, but admit that it possesses a slight degree of cohesiveness, and when necessary can be built up like cohesive gold by using deeply serrated pluggers."

Dr. Benjamin Lord says, "It is said that we know the world, or learn the world, by comparison. If we compare tin foil with gold foil, we find that the tin, being softer, works more kindly, and can be more readily and with more certainty adapted to the walls, the inequalities, and the corners of the cavities.

"We find also that tin welds—mechanically, of course—more surely than soft gold, owing to its greater softness; the folds can be interlaced or forced into each other, and united with more certainty, and with so much security that, after the packing and condensing are finished, the mass may be cut like molten metal.

"I contend moreover that for contouring the filling or restoring the natural shape of the teeth, where there are three walls remaining to the cavity, tin is fully equal to gold, and in some respects even superior; as tin can be secured, where there is very little to hold or retain the filling, better than gold, owing to the ease and greater certainty of its adaptation to the retaining points or edges of the cavity.

"It will be said, however, that tin fillings will wear away. The surfaces that are exposed to mastication undoubtedly will wear in time; but the filling does not become leaky if it has been properly packed and condensed, nor will the margins of the cavity be attacked by further decay on that account.

"Altogether, I believe that we can make more perfect fillings with tin than we can with gold, taking all classes of cavities; but it must not be understood that it is proposed that tin should ever take the place of gold where the circumstances and conditions indicate that the latter should be used. Of course, the virtue is not in the gold or the tin, but in the mechanical perfection of the operation, and tin having more plasticity than gold, that perfection can be secured with more ease and certainty.

"If we compare tin with amalgam, we must certainly decide in favor of the former and give it preference; as if it is packed and condensed as perfectly as may be, we know just what such fillings will do every time. We know that there will be no changes or leakage of the fillings at the margins; whereas, with amalgam, the rule is shrinkage of the mass, and consequently the admission of moisture around the filling, the result being further decay. It is not contended that this is always the result with amalgam, but it is the general rule; yet we must use amalgam, as there are not a few cases where it is the best that we can do; but it is to be hoped, and I think it may be said, that as manipulative skill advances, amalgam will be less and less used. For so-called temporary work, very often I prefer tin to gutta-percha, as it makes a much more reliable edge and lasts longer, even when placed and packed without great care."—N. Y. Odon. Society Proceedings, page 51, 1894.

One of the main reasons which induced the writer to begin the use of tin foil (Stannum Foliatum) for filling teeth, in 1867, was the fact that amalgam filling failures were being presented daily. Believing that tin could do no worse, but probably would do better, we banished amalgam from the office for the succeeding seven years, using in the place of it tin, oxychlorid, and gutta-percha. Since that time we have seen no good reason for abandoning the use of tin, as time has proved it worthy of great confidence. There is no better dental litmus to distinguish the conservative from the progressive dentist.

If we take a retrospective view and consider what tin foil was thirty years ago, we do not wonder that so many operators failed to make tight, good-wearing fillings. As it came from the manufacturer it looked fairly bright, but after being exposed to the air for a short time it assumed a light brassy color, and lost what small amount of integrity it originally possessed. This tin was not properly refined before beating, or something was put on the foil while beating, so that it did not have the clean, bright surface and cohesive quality which our best foil now has. No. 4 was commonly used, but it would cut and crumble in the most provoking manner. Fillings were made by using mats, cylinders, tapes, and ropes, with hand-pressure, on the plan for manipulating non-cohesive gold foil, but it was difficult to insert a respectable approximal filling.

From the best information obtainable, the writer believes that Marcus Bull (the predecessor of Abbey) was the first to manufacture and sell tin foil in the United States, as he began the manufacture of gold foil at Hartford in 1812.

Several years ago a radical change came about in the preparation of tin foil, for which the manufacturer should have his share of the credit, even if the dentist did ask for something better, for the quality depends largely upon the kind and condition of the tin used and on the method of manufacture.

For making tin foil for filling teeth, the purest Banca tin that can be obtained is used. The tin is melted in a crucible under a cover of powdered charcoal. It is then cast into a bar and rolled to the desired thickness, so that if No. 6 foil is to be made, a piece one and one-half (11/2) inches square would weigh nine grains. This ribbon is then cut into lengths of about four feet, and spread on a smooth board slanted, so that the end rests in a vat of clean water.

Then apply to the exposed surface of the ribbon diluted muriatic acid, and immediately wash with a strong solution of ammonia. Turn the ribbon and treat the other side in the same way. It is then washed and rubbed dry. The object of using the acid is to remove stains and whiten the tin, and the ammonia is used to neutralize the effect of the acid.

The strips are then cut into pieces one and a half inch square, filled into a cutch and beaten to about three inches square. It is then removed from the cutch and filled into a mold, and further beaten to the desired size. When the ragged edges are trimmed off, the foil is ready for booking.

It takes skill and experience to beat tin foil, for it is not nearly as malleable as gold; up to No. 20 it is usually beaten, but higher numbers are prepared by rolling. In each case the process is similar to that employed in preparing gold foil. The number on the book is supposed to indicate the weight or thickness of the leaf. On the lower numbers the paper of the book leaves its impression.

On weighing sheets of tin foil from different manufacturers a remarkable discrepancy was found between the number on the book and the number of grains in a sheet, viz: Nos. 3, 4, 5, weighed 7 gr. each; No. 6, 9 gr.; No. 8, from 9 to 18 gr.; No. 10, from 14 to 15 gr.; No. 20, 18 gr. In some instances the sheets in the same book varied three grains. We submit that it would be largely to the advantage of both manufacturer and dentist to have the number and the grains correspond. No dentist wishes to purchase No. 8 and find that he has No. 18; no one could sell gold foil under like circumstances. Of the different makes tested, White's came the nearest to being correct. The extra tough foil which can now be obtained is chemically pure, and with it we can begin at the base of any cavity, and with mallet or hand force produce a filling which will be one compact mass, so that it can be cut and filed; yet in finishing, it will not bear so severe treatment as cohesive gold. Always handle tin foil with clean pliers, never with the fingers; and prepare only what is needed for each case, keeping the remainder in the book placed in the envelope in which it is sold, otherwise extraneous matter collects upon it, and it will oxidize slightly when exposed to the air for a great length of time.

Before using tin foil, a few prefer to thoroughly crumple it in the hands or napkin, under the impression that they thus make it more pliable and easier to manipulate.

A piece of blue litmus paper moistened and moved over a sheet of tin foil will occasionally give an acid reaction, probably owing to the acid with which it is cleaned before beating not having been thoroughly removed. Foil held under the surface of distilled water and boiled for five minutes, then left until the water is cold, removed and dried, shows it has been annealed, which makes it work easily, but not as hard a filling can be made from it as before boiling.

In selecting and using this material for filling, we are able fully to protect the cavity; and if we understand the material, and how to manipulate it, we will surely succeed. This statement demands serious attention, and appeals to every one who is anxious to practice for the best interests of his patients; then let us make a thorough study of the merits of the method and material.

Until recently, the term cohesion had but one special meaning to dentists, and that as applied to gold for filling teeth; being understood as the property by which layers of this metal could be united without force so as to be inseparable. The writer claims that good tin foil in proper condition is cohesive when force is applied, and can be used for filling teeth in the same manner in which cohesive gold foil is used. This claim has been confirmed by several dentists, as noted in another part of this volume.

Cohesion is the power to resist separation, and it acts at insensible distances. The integral particles of a body are held together by cohesion, the constituent parts are united by affinity.

The attraction between atoms of pure tin represents cohesion. Marble is composed of lime and carbonic acid, which are united and held together by affinity.

The condition which obtains in the tin may be called cohesion, adhesion, welding, or interdigitation, but the fact remains that layers of tin foil can be driven together into a solid mass, making a tight filling with less malleting than is required for gold; if it is overmalleted, the receiving surface is injured.

On account of its pliability it is easily adapted to the walls and margins, and a perfect fit is made, thus preventing capillary action and preventing further caries. Of all the metals used for filling it is the best tooth-preserver and the most compatible with tooth-substance, and the facility with which a saving filling can be made largely commends it.

Tin has great possibilities, and has already gained a high position as a filling-material. Upon the knowledge we possess of the possibilities and limitations of tin as a filling-material, and our ability to apply that knowledge, will largely depend our success in preserving teeth.

It is a good material for filling many cavities in the temporary teeth, and children will bear having it used, because it can be placed quickly, and but little force is required to condense one or two layers of No. 10 foil. The dentin in young teeth has a large proportion of organic material, for which reason, if caries takes place, many believe it is hastened by thermal changes. Gold fillings in such teeth might prevent complete calcification, on account of the gold being so good a conductor; but if tin is used, there is much more probability of calcification taking place, because of its low conductivity and its therapeutic influence. It does not change its shape after being packed into a cavity. Under tin, teeth are calcified and saved by the deposit of lime-salts from the contents of the dentinal tubuli. This is termed progressive calcification.

Like other organs of the human body, the teeth are more or less subject to constitutional change. The condition in which we find tooth-structure which needs repairing or restoring should be a sure indicator to us in choosing a filling-material. Up to the age of fourteen, and sometimes later, we find many teeth which are quite chalky. In some mouths also, at this period, the fluids are in such a condition that oxychlorid and oxyphosphate do not last long; for some reason amalgam soon fails, while gutta-percha is quickly worn out on an occlusal surface. In all such cases we recommend tin, even in the anterior teeth, for as the patient advances in years the tooth-structure usually becomes more dense, so that, if desirable, the fillings can be removed, and good saving operations can be made with gold. By treating cases in this manner very little, if any, tooth-structure is lost.

The teeth of the inhabitants of Mexico and Guatemala are characteristic of their nervous and nervo-lymphatic temperaments; children ten years of age often have twenty-eight permanent teeth, and they are generally soft or chalky, but our dentists there report good success in saving them with tin.

In filling this class of teeth, we should be very careful not to use force enough to injure the cavity-margin, for if this occurs, a leaky filling will probably be the result. Still, we have seen some cases where slight imperfections at the margin, which occurred at the time of the filling or afterward, did no harm, because the deposit of tin oxid filled up the ends of the tubuli, thus preventing caries. We believe that this bar to the progress of caries is set up more frequently when tin is used than with any other metal under like conditions.