Tin Foil and Its Combinations for Filling Teeth

by Henry Lovejoy Ambler

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.