This is an outline ot 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. Kow 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.

Take a small piece of plate sufficient to cover the back of the tooth, and cut two holes in it to admit platinum pins. Having done this, cut off the pins, leaving sufficient to rivet the plate quite close to the tooth. Now tile oh the edges of the backing, so that none is visible, taking care that the hacking is long enough to rest on the plate when the tooth and plate are in position on the model. If bands or clasps are to be attached they should be made to fit the teeth they are to embrace quite accurately, bending up with smooth pliers. Supposing the plate is 16-carat gold, the bands or clasps should be of another quality - a gold which contains a certain amount of platinum, which makes it very tough. The plate being ready and made to tit quite close to the necks of standing teeth, so as to prevent any food getting between plate and palate, place the plate on the model, the tooth in position, and the bands or clasps, taking care that these just rest on the plate; retain them in position by applying a little warm beeswax and resin mixed, and the case will be ready for soldering.

Mix a little plaster-of-Paris with a little pumice-powder and water till rather stiff, and spread it on the soldering-coal. Take the plate, with attachments, off the model very carefully, and embed them in the plaster and pumice, bringing it well round the tooth and clasps, so that they remain stationary; then allow to set. Having done this, pour boiling water over the whole until every particle of wax is removed, and allow to stand and dry, say, for one hour. Place the soldering-coal in a, warm place, allowing the whole to warm through; grind lump borax on a slab with water, then with a camel-hair pencil paint the parts to be united - tooth, clasps, and pins at back of tooth; cut small pieces of gold solder and place them along the line of union. The soldering requires much care, as if the flame is directed too suddenly the teeth will crack and be quite spoilt. First direct the flame all round the bedding of pumice and plaster, gradually bringing it to the case until this reaches a dull red heat; the solder will then begin to flow. Great care is required to exclude any draught or cold air coming in contact with the case, or the teeth will crack instantly.

Allow to cool very gradually, remove the-hedding from the coal and place in water, when it will break up; wash the case and then with small half-round files and scrapers remove any projections of solder; remove all file-marks with water-Of-Ayr stone and water. Heat one tablespoonful of nitric acid with two tablespoonfuls of water in a porcelain pan over a spirit lamp, place the case in it. and it will assume its natural colour. With the circular brush of the lathe, polish first with very line pumice and water, finally with crocus and oil. Then wash thoroughly, and the case is ready for the patient's mouth. Of course, skill in theart of mechanical dentistry plate work comes only with experience.