US2889598A - Dental pattern - Google Patents

Description

June 9, 1959 B. H. LUND'QUIST ET AL 2,889,598 DENTAL PATTERN Filed Jan. 17, 1957 7/ INVENTOR. Q am United DENTAL PATTERN Birger H. Lundquist, Amherst, and Ralph E. Fentner, Cheektowaga, N.Y.

Application January 17, 1957, Serial No. 634,663

3 Claims. (Cl. 22--164) This invention relates to a pattern for and method of making dentures and bridgework and more particularly to a pattern used in producing in metal the lingual and occlusal portions only of the artificial teeth of fixed or removable partial dentures and bridges, the remaining portions of the teeth being completed in plastic in the form of a solid dummy, spacer or pontic.

One of the principal objects of the invention is to obtain precision and uniformity as well as a substantial saving in labor and material in modeling the lingual and occlusal portions of the teeth of artificial dentures and bridges, this being accomplished by providing a pattern in the form of a concavo-convex shell made of a plastic which softens under the application of heat and which conforms to the particular tooth to be substituted so that theshell can be placed in position in a model of the jaw of the patient, reshaped with a hot spatula or built up by the application of wax to conform to the patients bite, jaw and remaining teeth, and then used as a pattern in making a metal casting of this part of the denture.

Another object is to provide such plastic shells in such form that the proper tooth form can readily be selected by the dentist and so that the dentist can readily remove a shell of the desired tooth form from a group of such shells.

Another object is to provide such shells in multiple units of identical shells, the shells of each unit conforming to a particular tooth, this enabling the dentist to restock only those units which require replacement.

Another object is to provide a pattern for the lingual and occlusal portions of teeth whichleaves exceptionally smooth and flawless lingual and occlusal surfaces in the metal part of .the "denture.

Another object is to produce a denture having metal lingual and occlusal portions of'the required thickness and strength.

Another object is to produce a pattern which will disintegrate without apparent residue in the investment in which the metal is 'cast.

Another object'is to provide an internal anchorage in the concave-convex metal casting for the plastic with which this casting is filled.

Other objects and advantages of the invention will be apparent from the following description and drawings in which:

Fig. 1 is a plan view of a portion of a patients jaw showing two teeth between which an artificial tooth is to be supplied in .the form of a fixed denture embodying the present invention.

:Fig. .2is a'view similar to Fig. vl showing the two teeth of the patient ground to anchor inlays for supporting the 'COIIC'aVO-LEOIIVCX shells conforming to the lingual and .occlusal surfacesof thetooth normally in the space appearingiiniFigs. -l and 2.

Fate-un ied June 9,

Fig. 4 is a fragmentary longitudinal sectional view taken on line 44, Fig. 3.

Fig. 5 is a transverse sectional view taken on line 55, Fig. 3. v

Fig. 6 is a fragmentary plan view of a model made of the portion of the jaw shown in Fig. 2. and showing a concavo-convex shell cut from the strip, Fig. 3, fitted between model reproduction of the patients teeth and anchored by bits of wax, this figure also showing the plastic pattern or shell reformed by the application of a hot tool and by the application of a bit of wax to conform it to the bite of the patient.

Fig. 7 is a sectional view of the shell taken on line 7-7, Fig. 6 and showing a wax sprue forming stem attached thereto.

Fig. 8 is a sectional view through a casting flask of a centrifugal casting machine and showing the pattern and sprue forming stem, Fig. 7, embedded in an investment.

Fig. 9 is a view similar to Fig. 8 and showing the pattern and sprue forming stem replaced with metal.

Fig. 10 shows the casting and inlays positioned on the model, Fig. 6, and soldered together.

Fig. 11 is a sectional view taken on line l1-lll, Fig. 10 and showing the denture completed by filling the cavity of the metal casting with plastic to vform the visible side of the artificial tooth of the denture.

The present invention relates to dentures of the type in which the lingual and occlusal faces of the artificial tooth or teeth, is made of metal, such as stainless steel, or gold alloys, to provide the required structural strength and resistance to grinding wear, this metal portion being recessed toward the outside. This metal portion is provided with metal anchorages which removably or permanently anchor to the natural teeth being bridged. The recess of the metal portion is filled with plastic of a color conforming to the patients teeth and which is built out to provide the labial or buccal surfaces of the tooth or teeth so that the artificial tooth or teeth will simulate the adjacent natural teeth.

As now practiced, following forming the natural teeth to accept the anchorages, such as a metal cap or inlay, and following making an impression and a model of this area of the patients jaw, a pattern of the artificial tooth or teeth is carefully sculptured in wax to conform to the bite, jaw and natural teeth of the patient. Following this the labial or buccal side of the sculptured wax tooth or teeth is hollowed out to provide a cavity. A metal casting, which can also be a one'piece casting, is then made or" the wax pattern and this casting is smoothed and finished and soldered to the anchoring caps or inlays or clasps which have previously been formed to anchor to the natural teeth. The cavity or cavities are then filled with plastic to provide a natural appearance to the labial or buccal sides of the denture and the denture is ready to be placed.

The sculpturing of the wax pattern is time consuming and requires skill, patience and care to obtain the required structural strength, bite and fit and it is the object of the present invention to greatly reduce the time, skill, patience and care required for this step by providing a pattern which is largely preformed and which requires only incidental reforming or rebuilding up to achieve the required structural strength, fit and bite of the metal casting.

As illustrative of the present invention, in Fig. l is illustrated a plan view of that portion of a human jaw in which includes a second bicuspid 11 and a second molar 1-2, the jaw having a space 13 from which the first molar was extracted. The invention is illustrated as providing an artificial first molar in the space 13 and which is anchored by inlays to the adjacent natural teeth 11 and 12 although it will be understood that the anchorage could be in the form of metal caps, for the teeth 11 and 12, or

could be removable clasps to these or other teeth. To accept the anchorage inlays, the teeth 11 and 12 are shown as provided with medial grooves 14 and 15, respectively, and in which the inlays are cemented. From .a wax impression (not shown) a hard setting artificial stone model is made, this having protuberances 11a and 12:! conforming to the patients teeth 11 and 12 and having a space 13:: conforming to the space 13 of the extracted first molar. In the pattern the protuberances 11a and 12a have grooves 14:: and 15a conforming to the grooves 14- and 15.

As a first step the dentist or laboratory technician can form, from metal, the inlays 14b and 15!), Fig. 10, these being shaped to fit and anchor in the groove 14a and 15a, respectively, of the model 10a and hence in the grooves 14 and 15 of the patients teeth 11 and 12. These inlays 14b and 1552 are later soldered to the metal casting of the lingual and occlusal sides of the artificial first molar to be placed in the space 13 all as hereinafter described although these inlays may be in the form of a single castmg.

The numeral represents a long narrow strip of a flexible synthetic plastic which softens by the application of heat and which has high tear strength and maintains its form but can be readily cut to any desired form. For this purpose, and to provide a casting of the required structural strength the sheet 20 is in the order of from .015 to .030 inch thick and is made of a thermo-plastic which softens at between about 150 to about 200 F. A plastic suited for this purpose is high impact polystyrene.

In the strip 20 shown in Figs. 3-5, it is provided on one side with a longitudinal series of shell-like, concaveconvex protuberances 21 spaced from each other and each identical in form. Each is in the form of the lingual face 22 and occlusal face 23 of a first molar normally present at the space 13 in the human jaw. The concavity of each protuberance or shell 21 is on the buccal and gingival or saddle sides thereof. The dentist or laboratory technician would have on hand twenty-eight different strips 20, each having protuberances conforming to a corresponding one of the twenty-eight human teeth, the end or wisdom teeth being excepted since these are never reconstructed into dentures. The dentist would use the tooth forms of the particular teeth the denture is to replace and since in the example illustrated the first molar from the space 13 is to be replaced, the protuberances 21 are in the form of the lingual and occlusal faces only of this particular tooth.

The dentist or laboratory technician then cuts one of the series of protrusions 21 at its base from the strip 20 as to produce a concavo-convex shell having a rim 24 and conforming to the lingual and occlusal faces of the tooth to be replaced. This shell, as a pattern, is then fitted in the space 13:! of the model 10h with its lingual and occlusal faces properly oriented with reference to the tooth form protubcrances 11a and 12a of the model. In so fitting, the rim 24 of the pattern or shell 21 will probably have to be cut and shaped to fit the gum and tooth portions of the model and after being so cut the pattern or shell 21 can be fixed in position by bits of wax 17 applied in molten form to bridge and connect the rim or edges 24 of the pattern 21 with the model 10a.

Following this, with a hot spatula having a temperature above the softening point of the pattern or shell 21,

the pattern or shell can be reshaped to conform to the jaw, teeth and bite of the patient. As an example, a flat 25 can be provided in the pattern or shell 21 by applying a hot spatula to this area and exerting the required pressure to produce this fiat in the pattern. T o conform to the bite of the patient it will generally be found that some areas of the occlusal surface of the pattern or shell 21 must be built up or extended outwardly. This can be done by applying a small blob 26 of molten wax to the portion of the pattern or shell 21 to be built up and this blob sculptured with a hot spatula into the required form. As compared with the former practice of sculpturing an entire tooth from wax and then hollowing out its buccal or labial side, it will be appreciated that the pattern or shell 21 is essentially preformed to the desired shape and also holiowed out so that all that is necessary is to reform it to fit the particular patient. This results in a saving in time, care, patience and skill and greatly facilitates this operation.

To provide a better anchorage for plastic, as hereinafter described. a small semicircular length 27 of Wire can be inserted into the interior face of the shell or pattern 21, using either a bit of molten wax or a hot spatula for this purpose. The bend of this piece of wire projects into the interior of the shell or pattern.

Following this conventional practice can be followed to complete the denture. Thus the pattern or shell 21 can be removed from the model 10a and a wax stem or sprue forming member 28 adhered thereto. The flask for centrifugal casting is shown as including a cylindrical ring 29 and an end head 30 which removably fits one end of the ring 29. This end head is shown as having an indented central portion 31 provided with a central hole 32. in the indented portion 31 is adhered a mass of Wax 33. The end of the wax sprue forming stem 28 is then adhered to the portion of the mass of wax 33 which is exposed through the hole 32. The end head 30 is then applied as the base of the ring 29 with the shell or pattern inside the ring. The ring 29 is then filled with a hard setting material to form an investment 34. The parts are then heated to a high temperature to melt out the wax 23, 33 and burn out the plastic shell or pattern 21. Accordingly, a cavity is left in the investment 34 which conforms to the shell or pattern 21, sprue forming stem 28, and the indented portion 31.

The flash or ring 29 is then inverted as shown in Fig. 9 and molten metal 40 forced centrifugally into the cavity formed in the investment 34 by the indented portion 31. The desk is then put in a centrifugal casting machine and the metal driven into the cavity.

This metal forms a metal shell 41 exactly conforming to the pattern or plastic shell 21, a sprue 42, and an excess of metal 43 at the outer end of the sprue. The semicircular piece of wire 27 is cast into the shell 41. The casting is broken out of the investment and the sprue ground off. It will particularly be noted that since the pattern 21 was essentially a smooth surfaced shell, and since any added wax should also be sculptured to have a smooth surface, the surface of the casting is also exceptionally smooth.

The inlays 14b and 15b are then fitted, respectively, in the grooves 14a and 15a of the model 10a. The metal shell 41 is then placed in proper position in the space 13a in the model and is soldered, as indicated at 45 and 46, to the inlays 14b and 15b.

Following this the interior of the metal shell 41 is filled with plastic 49. This plastic flows around the semicircular piece 27 of wire which forms an anchor for the plastic when the latter hardens. The plastic is selected to color match the patients teeth 11 and 12 and the vertical face 50 thereof is sculptured to provide a buccal face conforming to that of a first molar.

The denture is then ready to be fitted into the patients mouth, the inlays 14b and 15b being fitted and cemented, in the grooves 14 and 15.

From the foregoing it will be seen that the present invention provides a partially preformed pattern for dentures of the class described which effects a substantial economy in time, and materials, care and patience of the dentist or laboratory technician and provide a high quality, high precision denture.

We claim:

1. A pattern used in producing in metal the lingual and occlusal portions of an artificial tooth in a denture, comprising a solid walled shell consisting substantially entirely of a convex lingual and occlusal surface on the outside and a conforming concave surface on the inside, the shell being open on the buccal and gingival sides thereof and being composed of a thermoplastic resin which softens under heat and having a substantially uniform wall thickness, measured from said inside to said outside surfaces, of from 15 to 30 thousandths of an inch whereby the pattern can be deformed, without diminution of said wall thickness, to conform to the bite of the patient and whereby when reproduced in metal as a casting the corresponding open buccal and gingival sides of the metal casting can be filled with moldable plastic which hardens to form the buccal and gingival surfaces of said artificial tooth.

2. A pattern as set forth in claim 1 wherein the thermoplastic resin is a high impact polystyrene which softens to a readily deformable condition at a temperature of from about 150 to 200 F.

3. A pattern as set forth in claim 1 and wherein a multiplicity of said shells are provided in the form of protuberances from a common sheet from which said shells are readily cut.

References Cited in the file of this patent UNITED STATES PATENTS 2,136,404 Wheeler Nov. 15, 1938 2,345,305 Thornton Mar. 28, 1944 2,362,507 Steinbeck et al. Nov. 14, 1944 2,461,416 Erdle et a1. Feb. 8, 1949 2,638,632 Glazyer May 19, 1953 2,700,184 Levine Jan. 25, 1955

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