How To Make Mechanical Dental Plates

This is an outline the processes and methods adopted in making a plate in mechanical dentistry. From an impression in composition make the plaster model not less than 3in. deep from the edge of the teeth to the base. When dry. immerse
it in melted stearine for fifteen or twenty minutes, then allow it to stand and dry.

Press over the model some thin sheet lead, sufficient to cover the palate; take it off, cut away the edges, and try it on the model. flatten the lead duplicate, lay it on the metal plate, carefully mark the latter with a pencil, and cut it out with shears Mix some casting sand, as sold at depots, with just sufficient water to bind it; if too damp, the zinc will spurt when being poured. Having thoroughly French-chalked the model all over, place it on the work-bench, base downwards; place the iron casting ring, which should be fin. deep and (5 in. across, on the bench encircling the model, and shape the sand well round the sides of model, pressing it down with the thumb until the ring is full, Give the ring a few sharp taps on the side with a small mallet and the model will fall out; turn it over and place carefully on the bench, and the mould is ready.

Melt some zinc in an iron ladle, taking great care not to make it too hot or it will burn and become useless, and when melted pour very carefully down the sides of the mould until full. When set, knock it out, and a facsimile of the plaster model will he found. Presuming the piece of plate is ready, anneal it over a spirit-lamp, and, when cold, bend it up with a pair of half-round smooth pliers , so that it will lie on the model. Now melt lead in a ladle sufficiently deep to allow the insert.on of the zinc model, which should be well oiled all over. Place it in the molten lead and allow to cool down, when it may be knocked out of the ladle, a few sharp blows with a hammer separating the zinc model and lead. The counterpart is now complete.

Commence striking up by placing the metal plate between them, taking great care that it is in the correct position. Place them together on a pad on the bench, and give a few hlows with a hammer of about five or seven pounds weight. Take out the plate and remove all signs of lead, and anneal it, as it becomes hard and liable to crack.

Place it between the part and counterpart and strike up again, until the plate fits the plaster model correctly. The tooth or teeth, it is supposed, have been ground to fit the gum.