Archibald McBride, of Pittsburg, Pa., in 1838, made a roll of a portion of a sheet of tin, and then used just enough gold to cover it, aiming to keep the gold on the surface, so as to have the filling look like one of all gold, and not with the idea of deriving any special benefit from the effects of wear or preservation as obtained by thus combining the two metals. The fee for a gold filling was one dollar; tin, fifty cents. Some operators have advocated using tin and gold (symbol Tg), rolled or folded together in alternate layers, thus exposing both metals to the fluids of the mouth; claiming that fillings can be made quicker, are not so subject to thermal changes, and can be inserted nearer the pulp than when gold is used. This may be true in comparison with gold, but these three claims are entirely met by using tin alone. Others say that this union of gold and tin will preserve the teeth as well as a correct gold filling, making no conditions or restrictions as to tooth-structure or location of cavity. They say that it preserves the cervical margin better than gold; that it expands slightly.

A description of some different methods of combining and manipulating tin and gold is subjoined:

(a) Two sheets of No. 4 cohesive gold and one of the same number of tin are used; place the tin between the gold, cut off strips, and use with hand or mallet force the same as cohesive gold; if non-cohesive gold is used, the strips can be folded into mats or rolled into cylinders, and are used on the wedging plan, the same as non-cohesive gold, or the strips can be folded back and forth in the cavity until it is full.

(b) Lay a sheet of non-cohesive gold, No. 3, on a sheet of tin of the same number, cut off strips, roll into ropes and use as non-cohesive gold. It is easily packed and harder than tin, and has a preservative action on the teeth. Line the cavity with chloro-balsam as an insulator against possible currents and moisture; especially should this be done in large cavities or chalky teeth.

(c) A sheet of non-cohesive gold, No. 4, is laid on a sheet of tin of the same number, cut into strips and rolled into cylinders, or folded into blocks, always in equal portions; then they will unite to the extent of two leaves. These fillings sometimes become a solid mass about the color of amalgam, and last very well, as the metals have become united by electrolysis. An excess of tin will be marked by lines or pits in the filling, showing where the tin has been disintegrated or dissolved by the chemical action which occurs on the surface exposed to moisture.

No doubt, good fillings have been made by the above methods, yet some were granular, gritty, and were easily removed, while others were quite smooth and hard; probably in the first instance the proportion of tin and gold was not proper,—that is, not equal; or it was not well condensed. Tin being the positive element, it is more easily acted on and disintegrated by electrolysis (chemical action of the fluids).

When this combination does become hard, it wears longer than tin on an occlusal surface, but we believe that in some cases where it was used the teeth could have been saved just as well with either tin or gold, or by filling part of the cavity with tin and the rest with gold.

If tin foil is laid on 22-carat gold and vulcanized, it becomes thoroughly attached and will take a tin polish; the attraction or interchange of atoms takes place to this extent.

This combination of tin and gold can be used at the cervical margin, or a cavity can be lined with it, and the remainder filled with cohesive or non-cohesive gold.

"Tin and gold (Tg) folded or rolled together in equal portions possesses a greater number of desirable properties than any other material, for it is easily adapted, has antiseptic action and a lower conductivity than gold. A new filling is harder than tin, softer than gold, but after a time it becomes as hard as amalgam. It oxidizes and thus helps make tight margins, and is very useful at cervical margins; generally discolors, but not always, and does not discolor the tooth unless a carious portion has been left, and then only discolors that portion. In oral fluids it is indestructible if well condensed, otherwise it is crumbly. There is no change of form, except a slight expansion, which does no harm. A weak electric current is set up between the gold and tin, and tin oxid is formed. The hardening and discoloration both depend upon the separation of the tin by the electrical action and its deposition on the surface of the gold. I generally prepare cavities the same as for non-cohesive gold, but a Tg filling may be held in a more shallow cavity and with less undercuts than for gold. Hand pressure is adopted, but a mallet may be used advantageously. Lay a sheet of No. 4 non-cohesive gold on a sheet of No. 4 tin, then cut into strips and twist into ropes; keep the tin on the outside, for it does not tear as easily as gold. Carry the material against the walls and not against the base, otherwise the filling will be flat or concave; but should this occur, then force a wedge-shaped plugger into the center of the filling, and drive the material toward the walls, and then fill the hole or remove all the filling and begin anew.

"In very deep cavities use a mat of Tg, dampened in carbolic acid and dipped in powdered thymol, as a base; this has an antiseptic action, and also prevents pressure on or penetration into the pulp.

"Drs. Abbot, Berlin; Jenkins, Dresden; Sachs, Breslau, have observed tin-gold fillings from fifteen to twenty-five years, and say that for certain cases it is better than any other material. I use square-pointed pluggers (four-cornered), as part of the packing is done with the side of the plugger. Tg is useful in partly erupted molars, buccal cavities under the gums, occlusal cavities in temporary teeth, cavities where all decay cannot be removed. Use Tg with a gold capping in small, deep occlusal cavities, cavities with overhanging walls, occlusal cavities with numerous fissures, large, deep occlusal cavities near the pulp, in proximal cavities.

"Line labial walls of incisors with non-cohesive gold, and fill the remainder with Tg. For repairing gold fillings I use Tg." (Dr. Miller, Berlin, Dental Cosmos, 1890.)

Dr. Jenkins, of Dresden, says, "I use Tg in soft, imperfect teeth, of which there are plenty in Germany, because it has pliability, adaptability, slight susceptibility to thermal changes, makes a water-tight joint, very useful at cervical margins, and can be used with a minimum amount of pressure. When packed dry and with the gold next to the tooth, discoloration occurs only on the surface; packed wet, the whole discolors. I do not attribute its success to electrical action. Lay a sheet of No. 4 tin on a sheet of No. 4 non-cohesive gold, fold so as to keep the gold on the outside; use the strip with lateral pressure, doubling it upon itself."

Dr. A. H. Thompson: "After several years' successful use of tin-gold, I commend it for approximal cavities, cervical margins, and frail walls. The oxid formed penetrates the enamel and dentin; if a filling wears down, cover the surface with gold."

Dr. Pearson: "I do not like tin and gold in alternate layers. I prefer No. 10 tin foil."

Dr. James Truman: "I believe that tin-gold has a positive value as a filling-material."

"I prepare tin-gold by taking a sheet of No. 4 non- or semi-cohesive gold, fold them together (or twist them) so as to have the gold on the outside, and then fill any cavity with it. Since adopting the above combination I have almost abandoned amalgam. This is recommended on account of its density, ease of insertion, capacity for fine finish, non-conducting and non-shrinking qualities, and compatibility with tooth-substance. Those who have not used it will be surprised at the rapidity with which it can be manipulated. It may be employed in any cavity not exposed to view, also in crown, buccal, and approximal fillings which extend into the occlusal surface, as it offers an astonishing resistance to wear. It can be used anywhere that amalgam can, and with more certainty of non-leakage, and it has the additional advantage that it can be finished at the same sitting. Care is necessary in manipulating it, so as to avoid chopping. I use hand pressure when filling, and the mallet to condense the surface." (Dr. A. W. Harlan, Independent Practitioner, 1884.)

"Pure tin foil is employed in connection with non-cohesive gold in filling proximal cavities in bicuspids and molars; a sheet of gold and a sheet of tin are folded together." (C. J. Essig: "Prosthetic Dentistry.")

Dr. Benj. Lord says, "A combination in which I find great interest is in the use of soft or non-cohesive gold with tin foil. This is no novelty in practice, but I think that, for the most part, too great a proportion of tin has been used, and hence has arisen the objection that the tin dissolved in some mouths. I am satisfied that I myself until recently employed more tin than was well. I now use from one-tenth to one-twelfth as much tin as gold, and no disintegration or dissolving away of the tin ever occurs. I fold the two metals together in the usual way of folding gold to form strips, the tin being placed inside the gold. The addition of the tin makes the gold tougher, so that it works more like tin foil. The packing can be done with more ease and certainty; the filling, with the same effort, will be harder, and the edges or margins are stronger and more perfect.

"The two metals should be thoroughly incorporated by manipulation. Then, after a time, there will be more or less of an amalgamation. By using about a sixteenth of tin, the color of the gold is so neutralized that the filling is far less conspicuous than when it is all gold, and I very often use such a proportion of tin in cavities on the labial surfaces of the front teeth.

"If too much tin is employed in such cases, there will be some discoloration of the surface of the fillings; but in the proportion that I have named no discoloration occurs, and the surface of the filling will be an improvement on gold in color."

"Dr. Howe. I would like to ask Dr. Lord whether, in referring to the proportions of tin and gold, he means them to be considered by weight?

"Dr. Lord. No, not by weight, but by the width of the strip of tin and the width of the strip of gold. I get the proportions in that way, then lay the tin on the gold and fold the gold over and over, which keeps the tin inside the gold.

"Dr. Howe. Will Dr. Lord tell us whether he refers to the same numbers of gold foil and tin foil; as, for instance, No. 4 gold and No. 4 tin?

"Dr. Lord. I use the No. 5 gold, and tin, I think, of about the same number, but I always use No. 5 gold, both cohesive and non-cohesive."—New York Odontological Society Proceedings, 1893, page 103.

"Tin and gold, in the proportions generally used, do not present a pleasing color; when finished, it looks but little better than tin, and after a short time it grows dark, and sometimes black. I use five parts of gold to one of tin, prepared as follows: Lay down one sheet of Abbey's non-cohesive gold foil, No. 6; upon this place a sheet of No. 4; upon this place a sheet of White's globe tin foil, No. 4; upon this another sheet of Abbey's non-cohesive gold, No. 4; upon this a sheet of No. 6. Cut into five strips and crimp; the crimped strips are cut into pieces a little longer than the depth of the cavity to be filled; some of the strips are rolled into cylinders, others are left open, because easier to use in starting a filling. The color of this combination is slightly less yellow than pure gold, and hardens just as rapidly as when the proportions are one to one, but does not become quite as hard. This preparation is non-cohesive, and should be inserted by the wedge process. I use it in the grinding surface of molars and bicuspids, buccal cavities in molars and bicuspids, cervical fissure pits in superior incisors, proximal cavities in bicuspids and molars. If proximal cavities are opened from the occlusal surface, the last portion of the filling should be of cohesive gold to withstand mastication. In simple cavities I place as many pieces as can be easily introduced, using my pliers as the wedging instrument to make room for the last pieces, and then condense the whole. If the cavity is too deep for this, I use Fletcher's artificial dentin as a base, because it partly fills the cavity and the ends of the cylinders stick to it. After an approximal cavity is prepared, use a matrix held in place by wooden wedges; the cylinders are about one-eighth of an inch long, and condensed in two or three layers so as to secure perfect adaptation; hand pressure is principally used, but a few firm strokes with a hand mallet are useful. When ready to add the cohesive gold for the grinding-surface, a few pieces of White's crystal mat gold should first be used, because it adheres beautifully; thus a perfect union is secured, but I never risk adding the gold without leaving a little undercut for it in the tooth. By this method we obtain a beautiful contour filling in a short time. Fillings should be burnished and then polished with a fine strip, or moistened pumice on a linen tape. Where cohesive gold is used for the entire filling, in many cases the enamel-walls, already thin near the cervical margin, are made thinner by the unavoidable friction of the polishing strips, but tin and gold is so soft that a good surface is obtained in a few moments, and this danger is reduced to a minimum. The surface is as smooth as a cohesive gold filling, while such a surface is impossible with non-cohesive gold. In cavities which extend so far beyond the margin of the gum that it is impossible to adjust the rubber-dam, I prepare the cavity as usual, then adjust a matrix, disinfect, dry, and fill one-third full with tin and gold, then remove the matrix, apply the rubber, place matrix again in position, and complete the filling by adding a little tin and gold, then pure gold." (Dr. W. A. Spring, Dental Review, February, 1896.)

Dr. T. D. Shumway says, "To have a scientific method of treatment, there certainly must be a recognition of what is known of the nature of tooth-structure. The method adopted more than a quarter of a century ago, and which is at present employed, does not accord with the teachings of the physiologist and microscopist; it is in direct opposition to natural law. Each new discovery in the minute structure of the teeth makes this more plain; pounding the teeth with a mallet cannot be defended on scientific grounds. That it has not resulted more disastrously is due to the wonderful recuperative energy of nature to repair injury. No one would think of attempting to arrest and prevent disintegration in any other vital organ by abrasion. Why, then, in operation on the teeth, should we reverse the plain, simple teaching of nature? Placing cohesive gold against the dentinal walls by pounding it to heal a lesion is opposed to natural law. Cohesive gold will not be mastered by force; if compelled to yield by superior strength, it seeks a way to release itself; it is easily coaxed, but not easily driven. Cohesive gold will unite with tin at an insensible distance just as cohesive gold unites with itself; this union takes place without force or pressure. Exactly what takes place when gold and tin are brought in contact in the way described we do not know; we can only say that there appears to be a perfect union. When cohesive gold was introduced to the profession, while it was softer than non-cohesive foil, it was found to resist under manipulation. This resistance is in accordance with the well-known law that all crystalline bodies, when unobstructed, assume a definite form. With gold the tendency is to a spherical form. The process of crystallization is always from within outward. The mallet was introduced to overcome the resistance caused by the development of the cohesive property. Pounding gold with a mallet only increases its crystallization. A crystalline body coming in contact with a fibrous one can neither be antiseptic nor preservative; a filling-material which possesses these properties must be one that corresponds or is in harmony with tooth-substance.

"In the interglobular spaces there is a substance which is called amorphous or structureless, and a filling to be in harmony with this substance should be amorphous or structureless in its composition. The only materials we have which meet these conditions are gutta-percha and tin. It is its structureless character that gives to tin its value. Coming in contact with the living dentin, it is easily adapted, and does not excite inflammation; it does not interfere with the process going on within the teeth to heal the lesion caused by caries. A wound from a bullet made of tin, unless it struck a vital part, nature would heal, even if the cause of the wound was not removed, by encysting the ball. This process of nature of repairing injury by encysting the cause is of interest to the dentist in the study of suitable filling-materials. Tin is very useful at the cervical margin of cavities; it acts as an antiseptic or preservative, and reduces the liability to subsequent decay. It is our endeavor to obtain a filling that will preserve the teeth and reduce the liability to, if not wholly prevent, secondary decay. The law of correspondence is of more consequence than the mechanical construction of the filling. Tin can be used without that rigid adherence to mechanical rule that is necessary to retain a filling of cohesive gold; thus less of the tooth needs to be sacrificed.

"Gold will unite with tin under certain conditions so as to form apparently a solid mass. By a combination of these metals, not by interlacing or incorporating one in the other, but by affinity, secured by simple contact, we have all the preservative qualities of tin combined with the indestructible properties of gold. For the base of the filling we have a material in harmony with tooth-substance, introduced in a way that is in accord with the law that governs all living bodies, and for the outside a crystalline substance that corresponds to the covering of the teeth. This covering of gold is a perfect shield to the base, and the field for the display of artistic skill in restoring contours is as broad as though gold was used entirely. Will a filling of this kind withstand mastication? There is in the economy of nature a provision made to overcome the resistance of occlusion. The teeth are cushioned in the jaw and yield under pressure. The elasticity of the substance of which the teeth are made is well understood. Ivory is the most elastic substance known. The teeth coming together is like the percussion of two billiard balls. Now a filling to save the teeth should correspond as nearly as possible with the tooth-substance; it should not be arbitrary, but elastic and yielding. Tin is interdigitous; it expands laterally, and is almost as easily introduced as amalgam, and when put in place does not have to be bound to be retained. Tin, with an outside covering of gold to protect it, makes a filling to which amalgam bears no comparison. In the light of scientific investigation there can be but one method—a method based upon the recognized principle that the filling-material and the manner of introducing it shall correspond to and be in harmony with the living, vital organism with which it comes in contact.

"After excavating, the cavity is treated with absolute alcohol, as cleanliness and thorough dryness are absolutely essential.

"The tin is put in with steel pluggers, after the method of wedging; it must be thoroughly condensed, so as to leave a smooth surface, and enough used to come up to where the enamel and dentin join.

"The effect is not produced by incorporating or interlacing the gold with the tin; we rely upon the affinity of the two metals to retain the gold; no undercuts, angles, or pits are made in the tin, dentin, or enamel. The gold, extra cohesive from No. 4 to 40, is made to adhere to the tin by simple contact, without pressure or force; the union is not mechanical.

"The instruments used for filling the remainder of the cavity with gold are Shumway's ivory points, which adapt the gold nicely to the margin.

"The set consists of five and were patented in 1881, and have been used by me since that time for manipulating cohesive gold. One 'point' is for proximal cavities in the anterior teeth; three 'points' of different sizes are for occlusal cavities; one 'point' for proximal cavities in bicuspids and molars and labial and buccal cavities; the sides, edges, and ends of the 'points' are used, as the purpose is simply to obtain contact.

"The 'point' shown full size in Fig. 8 is of more general application than any of the others, and is used for proximal cavities in bicuspids, also labial and buccal cavities. The handle is made of ebony, and has a silver ferrule, from which the ivory extends to the end and completes the instrument.

"The metal pin in the end of the handle is for picking up and carrying the gold."



Tin has been used successfully for completely lining cavities, filling the remainder with gold; it is also useful for repairing gold fillings.

Two or three thicknesses of tin foil may be pressed into a cavity with a rubber point or hard piece of spunk, allowing it to come well out to the margin; filling the rest with amalgam.

"As a lining it presents to dentin an amalgam of tin and mercury which does not discolor the dentin like ordinary amalgam, and helps do away with local currents on the filling, which is one cause of amalgam shrinkage in the mouth." (Dr. S. B. Palmer.)

When caries extends to the bifurcation of roots, make a mat of two or three layers of tin, place it in the bifurcation and use it as a base in filling the rest of the cavity with amalgam.

Tin is second in importance in alloys for amalgam, as it increases plasticity, prevents discoloration, reduces conductivity and edge strength, retards setting, favors spheroiding, therefore should not be the controlling metal.

It will be noticed that when cavities are lined with tin foil, it only constitutes a small part of the filling, and that it has not been melted with the other metals in the alloy before being amalgamated.

A thick mat of tin has been recommended as a partial non-conductor under amalgam fillings.

Plastic tin can be made by pouring mercury into melted tin, or by mixing the fillings with mercury at ordinary temperatures; it has a whitish color, and if there is not too much mercury it occurs in the form of a brittle granular mass of cubical crystals. Generally amalgams of tin and mercury do not harden sufficiently, but forty-eight parts of mercury and one hundred of tin make a fairly good filling, said to have a therapeutical value; it should not be washed or squeezed before using, and "is not a chemical combination."

"Tin unites with mercury in atomic proportions, forming a weak crystalline compound." (Dr. E. C. Kirk.)

Mercury and tin readily unite as an amalgam under ordinary circumstances, and form a definite chemical compound having the formula Sn_{2}Hg. (Hodgen.)

Another preparation of tin is known as stannous gold; it is manufactured in heavy sheets and used the same as cohesive gold foil, and can be easily manipulated, for it is rather plastic.

Crystal tin for taking the place of tin foil:

"Take chemically pure hydrochloric acid and dissolve tin foil in it until a saturated solution is obtained; this may be done speedily by heating the acid to a boiling point, or the same thing can be accomplished in a few hours with the acid cold; it is then chlorid of tin. It is then poured into a clean vessel and an equal quantity of distilled water added; then a clean strip of zinc is plunged into the solution, and tin crystals are deposited on the zinc; when there is sufficient thickness on the zinc, remove both, and slip the crystals off from the zinc into pure water, clean the zinc thoroughly, and reinsert for another coating. The character of the crystallization will be modified by the extent of the dilution of the solution in the first place. Wash the tin in pure water until all traces of the acid are removed, or a few drops of ammonia can be added to neutralize the acid. It was suggested that it would be desirable to have some acid remain in the tin for filling teeth in which there is no sensitive dentin. We have put in a few fillings, and it works beautifully, and makes firmer fillings than foil. It must be kept in water (probably alcohol is better). It is pure tin, unites perfectly, and works easier than foil." (Dr. Taft, Dental Register of the West, 1859.)

For some years it was considered the best practice to enlarge all root-canals and fill them with gold; in many of these cases the crown cavities were filled with tin.

Tin has been used for filling root-canals, but should there happen to be any leakage through the foramen or tooth-structure, the tin will discolor, and there may be infiltration into the crown, thus causing discoloration, which might be objectionable if the crown was filled with gold. Chloro-percha, gutta-percha, and oxychlorid of zinc are much better for this purpose.

The apical quarter of a canal has been filled with tin, and the remainder with cement. Tin can be used for filling root-canals. Roll on a broach small triangular pieces of the foil into very small cone-shaped cylinders, carry to place, then withdraw the broach, and force in the cylinder with the same or a larger broach; sometimes it is necessary to use another broach, to push the cylinder off from the one on which it is rolled. Another method is to carry and pack into the canal by means of a broach, very narrow strips of No. 10 or 20 foil; or the apical third of the canal could be filled with gold and the rest with tin.

"About four years ago I concluded to try tin for filling root-canals; then I began to look for patients whose general health was good, who had strong, hardy-looking teeth, and kept their mouths in good condition. I found one who answered all my requirements, with a molar to be filled, and they would not have it filled with gold, or could not, on account of the expense. I filled the canals with tin and the crown with amalgam. After filling thirty-eight molars in this way I stopped for developments. In six or seven weeks a lady returned with an inferior molar abscessed, but at the time it was filled the circumstances were such that it could not be properly treated. In nine months a gentleman for whom I had filled four molars returned with an inferior one abscessed. This is the sum-total of abscessed teeth where tin was used in the root-canals, at the end of four years. The others are in good condition, as I have seen them every six months. The roots were treated from four to six weeks with carbolic acid before filling." (Dr. A. W. Harlan, Missouri Dental Journal, 1872.)

"Tin foil is just as good as gold for filling root-canals, as it is entirely innocuous and sufficiently indestructible, while its softness and pliability commend it. Where gold is to be used for the crown, it is better to fill the bulbous portion of the pulp-cavity with gold also, so as to weld these portions of gold together. The success of Dr. Harlan's treatment was about equal to what might be expected from the same number of teeth where the canals had been filled with gold." (Editor, Missouri Journal.)

Shavings turned from a disk of pure tin have been used in combination with Watts's sponge gold for filling teeth, either by making a portion of the filling from each metal or using them indiscriminately.

A mat of tin foil dipped in chloro-percha can be used to cap an exposed pulp, or a concave tin disk can be used for the same purpose. A mat of tin has been used over a slight exposure of the pulp, because of its slight conduction of heat and cold, thus avoiding much thermal irritation and stimulating recuperation.

Some use Robinson's fibrous material as a surface for tin fillings, thinking that it is harder and will wear longer because of the erroneous notion that it has platinum in it.



CHAPTER IX.

Tin has been recommended for temporary fillings in sensitive cavities, because it is soft and easily packed in contact with the walls, has therapeutic value, and after a time, when the temporary filling is removed, the cavity is not as sensitive as formerly.

It has been observed that starting gold in a sensitive cavity causes pain, but starting tin in the same place seldom does.

As long as tin preserves its integrity it preserves the tooth, therefore tin fillings should not be repaired with amalgam, as their integrity may be destroyed. Cavities can be partly filled with tin and completed with sponge, fibrous, or crystalloid gold, after the manner described for beginning with tin and finishing with gold foil.

"I advocated tin at the cervical wall, cervico-lingual and cervico-buccal angles to the thickness of 24 plate. Then complete the filling with gold. Some of my most successful efforts in saving soft teeth have been made in this way. This method has great value over gold for the whole filling, but there are two objections to it: First, it imparts to the cervical border the color and appearance of decay, so that in three cases where an instrument passed readily into the tin I have removed the fillings, without any necessity for it, not even finding any softening of the margins. Second, its use requires the same conditions of dryness, shape of cavity, delicate manipulation, inconvenience to patient, and strain upon the operator as when gold is used alone." (Dr. D. D. Smith, Dental Cosmos, 1883.) He admits that this method saves soft teeth and also cervical margins. Do not those two very important factors more than counterbalance the color, and oversight of the dentist?

Dryness is an essential in making the best filling with any material, and the time and strain consumed by the majority of operators in filling with tin is not more than one-half what it is in using gold.

"I use tin at the cervical margin of all proximal cavities in bicuspids and molars. I prepare a matrix of orange-wood to suit each case, letting it cover about one-third of the cavity, then fill with tin condensed by hand force and automatic mallet; now split the matrix and carefully remove it piece by piece, so as not to disturb the tin; then trim and finish this part of the filling. Make another wooden matrix, which covers the tin and remainder of the cavity, and fit it snugly to place. Use a coarsely serrated plugger and begin packing non-cohesive gold into the tin, letting it fill about one-third more of the cavity; then complete the last third (surface) with cohesive gold. I have tested this method for twenty years, and it has given me splendid results. I always tell patients that there will appear sooner or later a slight discoloration near the gum, which must not be mistaken for caries." (Dr. A. P. Burkhart.)

Another use for tin in the operating-room is found in Screven's "Gutta-percha-coated Tin Foil," a cohesive, antiseptic non-conductor, of which the inventor says: "Cement fillings that have been kept dry for ten hours after mixing will be much harder than those soon exposed to moisture, and they will retain that hardness though exposed to moisture afterward. This preparation will keep a filling perfectly dry in the mouth, and when removed the filling will be found hard as stone. There is nothing better for lining cavities, holding nerve-caps in position, holding a preparation in place when devitalizing a pulp where the tooth is so much broken away as to make it difficult to prevent a filling showing through the enamel, and for many other purposes."

High-heat gutta-percha has been used as a base in deep occlusal, buccal, and approximal cavities, completing the fillings with tin. Occlusal cavities may be filled with tin; then after the filling is condensed and finished, drill out the center and fill with cohesive gold, not cutting away the tin so as to expose the margin; such fillings wear well, as much of the attritial force comes on the gold portion of the filling.

With the exception of the part in brackets, the following article is from the British Journal, May, 1887:

"If a person eats an oyster stew at 130 deg. F., a gold filling would carry the difference between the temperature of the stew and that of the mouth, 130 - 98 = 32 deg., almost undiminished to the bottom of the cavity; allowing 2 deg. of diminution, then the cavity around the gold filling has assumed 128 deg.; now the person feels warm and drinks ice-water at 32 deg.. Taking into consideration the specific heat of the gold filling, it will assume about 40 deg., which it carries with a diminution of the cold of about 4 deg.,—that is, as if it was 44 deg.,—into the interior of the cavity; then the cavity will assume 44 deg., the difference within one-tenth of a minute being 128 - 44 = 84 deg., a change which would produce a violent inflammation in any organ which was not accustomed to it. This derangement in the tooth means interruption of circulation, and young teeth will be most affected.

"Thermal effect depends on heat-conducting power [gold is nearly four times as good a conductor of heat as tin] and also on specific heat, so the more the latter approaches that of the tooth the less it is liable to produce sudden changes [thus favoring tin]. Specific heat manifests itself by the speed of changes, while the heat-conducting power influences the intensity [then the intensity of heat in a gold filling would be three or four times as much as in a tin filling]. In speed gold produces this change in one-tenth of a minute" [tin in one-fifth,—that is, gold absorbs heat and expands about twice as fast as tin].

In 1838 Dr. J. D. White introduced sharp-wedge-shaped instruments for filling teeth, and he claims to have been the first to use them; they pack laterally as well as downward, and present as small a surface to the filling as possible, so that the greatest effect may be produced upon a given surface with a given power. Rolls of either tin or gold are made by cutting any desirable portion from a sheet of No. 4 foil; cut this portion once transversely, place on a napkin or piece of chamois, then with a spatula fold a very narrow portion of the edge once upon itself; then with the spatula resting on the thickened edge draw the spatula away from it with gentle pressure, and the foil will follow in a roll.



The old method of using rolls, ropes, and tapes or strips is the same, but we will describe one method of using tapes. (See Fig. 9.) A strip is a single thickness of foil in ribbon form; a strip folded lengthwise once, twice, or more forms a tape of two, four, or more thicknesses of foil. The tin foil should be cut into strips and folded into tapes proportioned in width and thickness to the size of the cavity. One end of the tape is carried to the bottom of the cavity and then forced against the side opposite the point where we intend to finish; now remove the wedge-shaped plugger and catch the tape outside of the cavity, and fold another portion against that already introduced, letting all the folds extend from the bottom to a little beyond the margin. Proceed in this manner, with care and sufficient force, until the cavity is full, using for the last folds a small instrument. Condense the surface with a large plugger, then go over it carefully with a small instrument, and if any part yields, force in a wedge-shaped plugger and fill the opening in above-described manner; condense, burnish, and trim alternately until the surface is level with the cavity-margin. By extending the folds from the orifice to the base of the cavity, the liability of the tin to crumble or come out is effectually prevented, and by putting it in with a wedge-shaped plugger it is pressed out into all depressions of the walls.

A later method of filling with tape or rope is to use wedge-shaped pluggers with sharp serrations, filling the ends of the cavity, and as the two parts approach each other that next to the wall should be in advance of the rest, thus an opening will be left in the center which can be filled with a smaller tape or rope.

Another old method: Take a piece of foil and roll it into a hard ball; then gradually work it into the cavity, being careful to have sufficient around the margin.

Still another suggested method: Roll a piece of foil into a loose ball, place it in the cavity, and pass a wedge-shaped plugger into its center. This has the effect of spreading the tin toward the walls of the cavity, the opening to be filled with folds in a way already described. The wedge is used as often as it can be made to enter, filling each opening with folds; then condense the surface, trim, and burnish.



The English give the Americans the credit of first using cylinders. Anyhow, Dr. Clark, of New Orleans, in 1855, used them made from non-cohesive gold, and also from gold and tin in alternate layers. (See Fig. 10.)

Cylinders were used which were a little longer than the depth of the cavity, introduced with wedge-shaped pluggers around the walls, each one being closely adapted to the margin; then another row was added, which was forced firmly against the preceding, continuing this process until the cavity was full. The wedge, having a smooth end and sides, is forced into the center so as to drive the tin toward the sides of the cavity, being careful not to split the tooth; the opening is then filled with a cylinder. Now force a smaller-sized wedge into the center of the last cylinder, and into the opening introduce another cylinder, proceeding in this manner until the filling is solid. Then condense the ends of the cylinders, trim, and burnish. For the same operation more recent pluggers are wedge-shaped, with sharp, deep serrations. In these cases the filling is retained by the general form of the cavity and wedging within a certain limit, and not by cohesion of the different parts. For a time tin cylinders were prepared and put on sale at the dental depots.

As far as we are aware, the first tin foil made use of in operative technics was by Dr. F. S. Whitslar, who removed a disk of German silver from an ivory knife-handle in 1845, then used hand pressure to fill the cavity with tin. In the college course of operative technics tin foil can be used, almost to the exclusion of gold foil, to demonstrate the manipulation of both cohesive and non-cohesive gold. Shavings scraped from a bar of tin are also useful in operative technics; they are more cohesive than foil.

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