Process for forming dental bridges and the like.

Application filed June 1, 1908. Serial No. 436,171.

To dll whom it may concern: ]

Be it known that I, Thomas C. ΙΙιγτγπτν- son, a citizen of the United States, residing . at Decorah, in the county of Winneshiek and ! State of Iowa, have invented certain new | and useful Improvements in Processes for ₍Forming Dental Bridges and the Like, of which the following is a description.

My invention relates to the production of that class of artificial or partially artificial teeth, known as bridges, crowns and the like and the object of my invention is to provide an accurate, convenient and extremely expeditious means for forming such teeth.

Tn the accompanying drawings wherein like or similar reference characters indicate i like or corresponding parts: Figure 1, is a plan view of a die plate for carrying my process into effect. Fig. 2, is a section taken substantially on line 2—2 of Fig. 1. Fig. 3, is a section taken substantially on line 3—3 of Fig. 1. Fig. 4, is a side elevation of a model formed in one of the cavities in the die plate. Fig. 5, is a model inclosed in a suitable investment to form a mold.

Tn the preferred form shown in the drawings 1, is a die plate formed of any suitable material and provided with any desired number, form and arrangement of dies or cavities, 2. 3 and 4 each preferably corresponding accurately with one or more articles or some portion of one or more articles which it is desired to produce. Tn the form shown each of the cavities 2 accurately corresponds to the form and size of a normal tooth and the cavities 3 and 4 to a plurality of normal teeth in their natural relation to each other. Several sizes of each tooth or combination of teeth are preferably provided so that a die or cavity may be selected which will accurately correspond with the size of the teeth of any designated person.

After selecting the desired cavity to be employed in a particular case, the operator fills the cavity, with any suitable substance which will accurately conform to the shape of the cavity and retain its shape to serve as a dummy or model 5 and xvhich may be volatilized or otherwise eliminated by heat or other convenient agency. Preferably a sheet of suitable wax is first warmed over a flame or in hot water until it is sufficiently plastic, then rolled to size desired to properly fill the cavity selected. The walls of the cavity are then preferably moistened with water or other suitable liquid and the softened wax carefully pressed into the cavity xvith a blunt instrument taking care to force the wax firmly against the sides 6 and 7 of the cavity and to its extreme bot- 60 tom 8 to insure an accurate model and the proper form at the bucco-occlusial point. Having properly filled the cavity any surplus wax may be removed with a heated spatula or other convenient means and the 65 completed model lifted out of the die. When a bridge is being constructed the abutments should noxv be made and fitted to the plaster or other model xvhich may be mounted upon an articulator in the usual or any desired 70 manner. The xvax dummy or model 5 is then carefully fitted bnccally and‘labio-distally trimming or otherwise forming the same to accurately fit in place. The xvax model xvill readily bend to conform to the shape of 75 the plaster model without seriously distorting or injuring its appearance. The model is completed by carefully forming the palatal surface to fit the plaster model so that an accurate xvax model of the finishing ⁸⁰bridge is provided.

When it is desired to provide a porcelain facing for all or a portion of a bridge, the buccal surface of the model may be employed as a pattern by xvhich to determine ⁸⁵the size of the facing desired, after which the buccal surface may be cut from the model xvith a knife or other suitable means and after oiling the pins upon the facing press the same into place, reinforce the ⁹⁰cutting edge of the facing, cool or permit the model to harden, remove the facing and insert suitable carbon points in the pin holes, which may be readily removed after the bridge is cast leaxung the metal part of the ⁹⁵bridge ready to receive the facings which may be easily cemented into place. A small pin or stem 9 is next forced into or otherxvise attached to the finished model to serve as a handle for supporting the model xvhile ¹⁰⁰it is being invested and also to serve as an inlet or runner by which molten metal may be introduced into the finished mold. The finished, xvax model is next invested in a suitably refractory porous material, such ^10ffor example, as a mixture of plaster of Paris and silica, to form a mold or casing 10 with a suitable cup or crucible 11 at the stem 9 to receive the molten metal.

As soon as the investing material has suffi- ¹¹⁰ciently set or hardened, the pin or stem 9 is withdrawn and the mold 10 is subjected

982,199 to sufficient heat to vaporize or burn the wax model and completely eliminate the same, leaving a mold with a suitably formed cavity to receive the molten metal to form the desired article connected by a small runner or opening to a cup or crucible 11. The walls of the mold are sufficiently porous to permit the escape of any imprisoned air so that when molten metal is placed in the crucible it may be forced into the mold to form an article.

The molten metal may be forced into the mold in any desired manner, for example, the molten metal, may be forced into the crucible 11 from a suitably constructed pump or the air may be exhausted from the mold cavity, thus permitting the metal in the crucible to enter the mold under ordinary atmospheric pressure, but as mechanism for forcing metal into the mold forms no part of my present invention, a further description of the same is unnecessary. After the cast is complete and the metal permitted to cool the mold is broken away and the finished article polished or otherwise finished, as. may be desired.