This material is easy to manipulate, but great care is required in condensing at cavity-margins, so as to make a tight filling, and also not injure the margins. It makes as hard a surface as tin foil, and can be cut, polished, and burnished so that it is smooth and looks well; it can be used in temporary or chalky teeth, as a small amount of force condenses it. By using a matrix proximal cavities can be filled from one-fourth to one-half full, and the rest filled with gold, relying on the form of the cavity to hold the gold, regardless of its connection with the fibrous material. If the surface is not overmalleted so as to make it brittle or powdery, a strip of No. 4 cohesive gold, of four or five thicknesses, may be driven into it with a hand mallet and plugger of medium serrations; this union is largely mechanical, but of sufficient tenacity to make manipulation easy, as the material makes a solid foundation to build upon. After exposure to the oral fluids, electrolysis takes place at the junction of the metals.
In 1884 Dr. Brophy said, "I have used Robinson's material for two years, and find it possesses good qualities, and can be used in deciduous teeth, first permanent molars, and cervical margins with better results than can be obtained with any other material by the majority of operators."
Malleted with deeply serrated pluggers, it will make a filling which will not leak. It has saved many teeth from caries at the cervical margin where it might have recurred sooner had cohesive gold been used.
In the mouth it changes color about the same as tin foil, and a few fillings did not maintain their integrity, but became crumbly and granular.
For conducting properties it ranks about with tin, and fillings can be made more rapidly than with cohesive gold. We have used ounces of it, but time has proved that everything that can be done with it in filling teeth can also be accomplished as well and in some cases better with tin foil.
In 1878 Dr. N. B. Slayton patented his Felt Foil, which was said to be tin cut into hair-like fibers by a machine, then pressed into small sheets and sold in one-half-ounce books, but it sold only to a very limited extent. Soon after this Dr. Jere Robinson, Sr., invented a machine and began the manufacture of a similar article, but he found he was infringing on the Slayton patent, so he purchased the Slayton machine and made satisfactory terms to continue his own manufacture of fibrous material. After this little was heard of Slayton's Felt Foil, but Robinson's was considerably used. The two materials look and are manipulated almost exactly alike. Dr. Robinson has both of above-mentioned machines now in his possession.
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."
[Illustration: FIG. 8.]
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.