302

PALATE MOLD AND FLASK.

bottom of the flask, the side being preferable. This half of the metal mold should be finished all it may need, when the other may be made by placing the palate patterns on the metal mold, filling the other half of the flask, and carrying out substantially the preceding steps.

The palate produced by either of these molds is shown in

Fig. 208. In connection with it is also shown the plate with clasps which secure it in position by attachment to contiguous teeth. The connection with the plate is by a pin of gold passing through a hole of the same size in the palate, the

LATEST FORM OF PALATE MOLD.

303

head on the pin being larger than the hole through which it is forced. The two pieces of palate made in mold Fig. 207 accomplish the same result when in use, as they are held together at the forward part by the pin and head, and a few stitches of silk secure them at the posterior part.

Another plan for a mold, and the one which the author has adopted for his large series of molds, is made in three pieces of metal, as shown in Fig. 209. It is the most simple and at the same time the most complete of any mold yet invented. It is inclosed in a flask like Fig. 207, but with the improvement that the resultant palate is complete in one piece, the same as that produced by the more complicated mold, Fig. 204. A represents the base of the mold

made in one half of the flask; B, the section which occupies the other half of the flask, and is placed on top of A in the same relation they hold in the cut, i. e., the under side of the section marked B fits to the surface marked A, and between these is the space for a portion of the palate. B, which we may call the middle section, represents one half of the palate on one of its sides, and the other half on the other side, the connection between the two divisions of the palate being through the opening in the center. The third section of the mold, C, turns over and fits on top of the middle section, and when inclosed in the flask makes the mold complete. When the flask is opened after the rubber is vulcanized, the palate will remain with the middle section, and can be removed by pulling the smaller part through the central opening.

304

PACKING THE MOLD WITH RUBBER.

The process of making a palate in any of these molds is by packing with rubber in substantially the same manner as when hard rubber is used for a dental base, with which process it is assumed the reader is familiar. By painting the surface of the mold with a thick solution of soap, or, better still, rubbing the mold over with hard soap previous to packing, the palate will be more easily removed after vulcanizing.

The rubber used for this purpose must be a more elastic compound than that used for a dental base-plate. Partially vulcanized hard rubber, which is sometimes used, is very objectionable. Not being completely cured by the vulcanizing process, it soon deteriorates in the mouth, becomes disintegrated, and all the objectionable ingredients of its composition made apparent. The compound used for elastic

DIRECTIONS FOR VULCANIZING.

305 fabrics of commerce will answer if made of selected materials, but for this purpose it ought to be especially prepared. The permanent value of an artificial velum is much enhanced by using only material made with reference to such use. Such a composition requires not only great care in the purity of its ingredients, but the proportions and the method of working the mixture will affect materially for better or worse the articles made from it. Some rubber compounds possess a durability greatly in excess of others, and consequent increased benefit to a patient wearing such an instrument. To obtain the best results, the rubber should be vulcanized for six hours between 230° and 260° of heat, beginning at 230° and increasing 5° per hour until the end.

CHAPTER XIV.

INTRODUCTION AND USE OF ARTIFICIAL VELA.

PRESUMING that hereafter many dentists will prefer to adopt one of the forms of palates already made rather than go to the trouble, with little or no experience in that direction, of making molds and producing them, the following directions for their successful application will be found valuable:

After the plaster cast of the fissure and adjacent parts has been made and proved as before described, select from the various forms and sizes of artificial palates one best adapted to the plaster model. It is not necessary that it should come to the apex of the fissure if the apex be within the hard palate; neither is it absolutely essential that it should reach completely to the apex if the fissure comes no farther forward than the posterior margin of the hard palate. But, if the fissure is short and does not come up to the palatine bone, it is better that the artificial palate fill the fissure to the apex. At all events, it must be broad enough to cover all of the remnant of the soft palate on each side of the fissure and anterior to the uvula. Place the palate in position on the plaster model, and proceed to make a temporary plate or attachment for the purpose of trying the palate in the mouth. A very easy method is to insert in the hole in the palate a bit of common iron wire of suitable size to fit into it, with the end on the oral side bent toward the front teeth. Pour a little plaster over the gum, as represented in the model, about this wire, and reaching back to where it is in