Tin Foil and Its Combinations for Filling Teeth

by Henry Lovejoy Ambler

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 Sn₂Hg. (Hodgen.)