Tin Foil and Its Combinations for Filling Teeth

by Henry Lovejoy Ambler

"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.