Many operators have not tried to unite the tin and make a solid mass; they seem to think that it cannot be accomplished, but with proper pluggers and manipulation it can be done successfully.
For large occlusal or proximal cavities, the tapes may be folded into mats, or rolled into cylinders, and used on the plan of wedging or interdigitation, and good fillings can be produced by this method, but the advantage of cohesion is not obtained, and more force is required for condensing. They are, therefore, not so desirable as tapes, especially for frail teeth. When using mats or cylinders, the general form of the cavity must be depended upon to hold the filling in place. To make the most pliable cylinders, cut a strip of any desired width from a sheet of foil and roll it on a triangular broach, cutting it off at proper times, to make the cylinders of different sizes.
A cylinder roller, designed by the author, is much superior to a broach. (See Fig. 7.) When the cavity is full, go over the tin with a mallet or hand burnisher, being careful not to injure the cavity-margin. Cut down occlusal fillings with burs or carborundum wheels, and proximal fillings with sharp instruments, emery strips or disks. After partially finishing, give the filling another condensing with the burnisher, then a final trimming and moderate burnishing; by this method a hard, smooth surface is obtained.
Fillings on occlusal surfaces can be faced with No. 20 or 30 tin, and burnished or condensed, by using a burnisher in the engine, but do not rely upon the burnisher to make a good filling out of a poor one.
By trimming fillings before they get wet, any defects can be remedied by cutting them out; then with a thin tape (one or two layers of No. 10) and serrated plugger proceed with hand or mallet force to repair the same as with cohesive gold.
Another method of preparing tin for fillings is to make a flat, round sand mold; then melt chemically pure tin in a clean ladle and pour it into the mold; put this form on a lathe, and with a sharp chisel turn off thick or thin shavings, which will be found very tough and cohesive when freshly cut, but they do not retain their cohesive properties for any great length of time,--perhaps ten or twenty days, if kept in a tightly corked bottle. After more or less exposure to the air they become oxidized and do not work well, but when they are very thin they are soft, pliable, and cohesive as gold, and any size or form of filling can be made with them.