US3102337A

US3102337A - Dental process and products

Info

Publication number: US3102337A
Application number: US1927A
Authority: US
Inventors: Mintz Charles
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-01-12
Filing date: 1960-01-12
Publication date: 1963-09-03
Anticipated expiration: 1980-09-03

Description

Sept. 3, 1963 v c. MINTZ DENTAL PROCESS AND PRODUCTS 2 Sheets-Sheet 1 Filed Jan. 12, 1960 INVENTOR.

CHARLES MINTZ BY W717 ATTORNEY Sept. 3, 1963 c. MINTZ 3,102,337

DENTAL PROCESS AND PRODUCTS Filed Jan. 12, 1960 2 Sheets-Sheet 2 E] [INVEST] Elf-l5- I .El. 1% EFELIMINATE WAX FROM MOLD BY MELTING CASTINMETAL INVENTOR. CHARLES MINTZ ATTORNEY f uniformity of results. 7 crown, one must first lubricate a die of the tooth'stump DENTAL PROCESS AND PRODUCTS Charles Mintz, Jackson Heights, N.Y.

(1 415 162d St, Whitestone 57, N.Y.) Filed Jan. 12, 1960, Ser. No. 1,927 14 Claims. (Cl. 32- -12) 'l"-he present invention relates to dentistry, and particularly to a novel method and means useful therein for the manufacture of dental crowns, bridges, pontics and the like, including attachments for the same, as hereinafter described and claimed.

The method which is generally employed in dentistry for the construction of a veneer crown involves a series of tedious and time-consuming steps with attendant non- In the art of constructing such a and then apply wax completely around all surfaces of the tooth. The wax is carved to conformv with the desired shape of the crown. After the simulated tooth surface has been fully shaped in the Wax, a window is curved in the frontal surface toprovide "a necessary void for subsequent reception of the veneeron the remainderof the crown.

The next ste balls, hooks or loops on the inner surfaces of the Wax pattern, to which the veneer can be attached. The wax pattern is finally removed, invested so as to form a mold, and gold is cast into the mold to conform with it.

After removal of the casting "containing the gold backing and loops disposed therein, a plastic facing is processed to the loops to forrn the completed crown.

It is apparent-that this procedure as presently used in dental practice requires a, very. long and tedious carving technique with skillful carving of the window and the application of the retention loops in the wax pattern so as i to properly process the plastic veneer.

Such technique, requiringvcare and skill at every stage, does not readily lend itself to uniformly successful results. Furthermore, the metallic loops-may show through the translucent plastic veneer and adversely affect the shading of the plastic soldered a female attachment which is fittedwith a male attachment carrying the bridge or pontic. The grinding operation is a delicate one so asnot to puncture the gold wall and is limited to the preparation of side walls which are perpendicular to the base.

It is an object of the present invention to provide a simplified, more economical and more efiicient method for preparation of dental crowns, bridges, pontics, and attachments for the same. p

Another object of'the invention is to diminish the timeconsuming carving operation involved in the preparation of veneer-receiving voids or windows;

Also an object ofthe present invention is a method for the preparation of Wax patterns for veneered dental crowns, bridges, .pontics and the like, in whichaveneerretaining Void orwindow of standardized shape and size I is employed.

A further object of the present invention is an improved is the insertion, through thewindow, and l proper positioning, of a number of retaining mushrooms,

1 of amale attachment, and

precision rests and clasps.

forming a tooth-simulating pattern composed of a normally solidwater-soluble material on a surface of a mount 3,102,331 Pat nted Sept. 3,11963 thereby facilitate the use of Another object is a preformed dental veneer or insert adapted'to form a temporary part of a wax pattern' Yet another objectof the present invention is eliminationof the need for and use of metal loops, balls or mushrooms for retaining the veneer, thereby eliminating any possibility that these loops or .the like may show through the veneer and affording the preparation of a, moreesthetic veneered crown or the like.

Also an object of the instant invention is a resilien veneer adapte d to exactly mate with a window provided in a metal replica of a tooth, said window being of a predetermined size and shape identical to that of theveneer. A principal feature of the present invention relates to of waxy material, The water-soluble portion encompasses an opening or window for later insertion of means for supporting or attaching artificial tooth structure. The waxy material with the water-soluble portion is shaped so as toform a consolidated, patternof a desired tooth.

'The water-soluble pattern is leached away from the waxy I practice is to attach a clasp projecting from the bridge to a the crown orto grind a slot inthe crown in which is materialwith an aqueous'solvent to form an opening for insertion of means for supporting the artificialtooth 'structure after casting. of the desired tooth pattern in metal.) In this opening, there can be inserted a facing veneer fol: example or a female attachment from a pontic or brid'geij i A preferred embodiment of the present invention relates toa process for the preparation of a veneered tooth replicay/hich comprises super-imposing a preformed pattern of {thewater-soluble material on the frontal surface of amount formed of waxy material, said'water-soluble pattern having the shape and perspectiveof a-tooth facing and encompassing a window having locking means extending therefrom, embedding said locking means in said waxy .material, shaping said waxy material and preformed-water-soluble Window pattern to form the desired finished tooth having said water-soluble pattern as the frontal surface thereof, and leaching said watersoluble preformed window pattern and the locking means thereon away from said waxy material with the aqueous solvent,

.said window-containing pattern having means for mating with said locking means recessed therein.

The invention further contemplates investing said window-containing pattern in a mold, reproducing, in saidmold, a metal replica of said windowscontaining wax 'pattern,.recovering said metal replica from said mold,

and inserting, in said windo -containing metal replica, means foraatta'chment of artificial tooth structure such as a resilient veneer having the same sizeiand shape as the aforesaid pro-formed water-soluble pattern. By virtue of the fact that the instant locking means, is integral with and constitutes an extension of the facing,

there are nometallic'projections in the form of retaining loops or hooks to show through or shadow the final veneer. a I

'Also within: the ambit of the present invention is an insert for waxed dental patterns. comprising a waters-olu'b'le preformedveneerwindow pattern having the shape and perspective of a tooth-facing and preferably e in the following description. The'invention will he described :further in connection with'the accompanying drawings which are to be con-,

method for attachment of a bridge or pontic to a crown involving a pie-formed void on the crown for insertion having locking means extending outwardly therefrom and adapted to beimbedded within a waxed dental pattern. 7 Various other-preferred embodiment-s will be apparent sidered as exemplary of the invention and which do not constitute limitations thereof. f r In the ,drawings, which constitute a schematic presen-;

tation of the instant process;

FIG. 1 is a perspective view of a die or model of a tooth stump which is to be crowned,

FIG. 2 illustrates the die of FIG. 1 to which a preliminary layer of wax has been applied,

FIG. 3 is a rear perspective view of a preformed watersoluble veneer window pattern in accordance with the present invention,

FIG. 3-A is a cross-section in elevation of the watersoluble pre-formed veneer window pattern of FIG. 3 along the line AA thereof,

FIG. 4 illustrates the waxed die of FIG. 2 to which the veneer window pattern of FIG. 3 has been applied,

FIG. 5 illustrates the application of the remainder of the necessary wax to form a consolidated pattern,

'FIG. 6 indicates, in schematic fashion, the leaching of the Water-soluble window pattern from the consolidated pattern of FIG. 5,

FIG. 7 indicates the structure of the wax pattern after removal of the water-soluble window pattern therefrom,

FIGS. 8-10 indicate, in schematic fashion, the procedural steps of investing the wax pattern of FIG. 7, eliminating the wax from the mold, and casting gold into the mold respectively which techniques are known,

FIG. 11 illustrates the cast gold crown,

FIG. 12 illustrates a plastic veneer window insert for the cast gold crown of FIG. 11,

FIG. 13 illustrates the final veneered crown,

FIG. 14 illustrates the structure of the wax pattern and cast crown serving as an abutment retainer for attachment of a bridge or pontic,

FIG. 15 is a plan view showing the female attachment inserted therein.

In FIG. 1, character 10, refers to a die or model of a stump to be crowned, the die being prepared in the usual manner from an impression of the actual'stump to be crowned. In the course of the present process, the lie is lubricated in the customary manner to facilitate release from the pattern to be prepared thereon.

After lubrication of the die 10, it is entirely covered with a preliminary layer of wax 11, as illustrated in FIG. 2. The preliminary layer of wax 11, completely covers the lubricated tooth die 10, but is a relatively thin coat, part thereof 12 forming the exposed frontal surface of the waxed die, i.e., the part which is to be veneered.

After the preliminary waxing step illustrated in FIG. 2, the waxed die is ready for application thereto of a preformed water-soluble veneer window. A suitable preformed window pattern is illustrated in FIGS. 3 and 3-A, and is shown applied to the preliminarily waxed die 11 in FIG. 4.

The pattern, indicated generally by character 13, is comprised of a window portion 14, which corresponds to the visible part of the final veneer, and a remaining portion or portions consisting of

lateral dovetail wings

15 and 15 and rearwardly depending lip 16, which together constitute the supporting and retaining means for the window portion 14 in the consolidated pattern of the desired finished tooth replica, as referred to hereinafter.

The window portion 14 is thicker than and protrudes forward or outward from the lateral dovetails. The thus raised window section is convex on its outer face 17 (not clearly visible in FIG. 3, but fully visible in FIG. 3-A), and is concave on its rear face '18. For the most part, these two faces are substantially parallel, thus providing, for a major part of its length, a window of substantially uniform thickness. The iower portion of the window sect-ion, however, tapers smoothly to a knife edge.

The forward or outer face '17 of the window section 14 is formed such that it has substantially the shape and periphery of the desired visible veneered portion of the final crown, i.e., the appearance of a natural tooth.

The outer faces 19 of the dovetail wings 15 are recessed behind the forward face 17 of the window portion 14 as a result of both tapering and curvature of the watersoluble insert pattern. (A stepped or relief type structure may also be used of course.) Each trapezoidal wing 15 extends from the window portion 14 at the lateral edges thereof, towards the base 20.

The water-soluble pattern is disposed on the pre1iminary wax layer and the rcarwardly depending lip 16 is embedded therein, as illustrated in FIG. 4. The remainder of the necessary wax is then applied to the pattern, and the wax is then carved to final shape, uniting with the exposed front surface of the water-soluble window to form a smoothly contoured consolidated pattern of the desired final veneered tooth replica, as illustrated .by FIG. 5.

As is apparent from FIG. 5 the dovetail wings 15 of the water-soluble insert are covered by and embedded in the final wax layer which, of course, is carved to be flush with the forward or convex surface 17 of the window portion.

The next step comprises leaching the water-soluble preformed veneer window from the consolidated pattern to form the final wax pattern, which, of course, then contains a void or cavity 21 corresponding to the configuration of the removed water-soluble pattern.

This leaching step is shown schematically on the drawing as FIG. 6. Any appropriate solvent such as distilled water may be employed, as will be referred to hereinafter. In some instances it may be desirable to deliberately syringe out the void 21 with solvent to insure complete removal of the entire water-soluble insert, and particularly the portions thereof which are embedded in and covered by the wax.

The final wax pattern formed after the pre-formed water-soluble veneer window pattern has been washed out of the wax pattern as illustrated in FIG. 7, wherein it is referred to generally by the character 22. This final wax pattern is then invested in a conventional molding compound in the usual manner, as referred to schematically in FIG. 8 of the drawing. The wax is then destroyed or eliminated from the mold in accordance with customary practice, e.g., by melting, as referred to in FIG. 9, and the wax pattern is then reproduced in the mold by casting in gold (FIG. 10) to form a gold replica of the windowcontaining final wax pattern of FIG. 7, this gold replica being referred to generally by the character 23 in FIG. 11. The gold crown is released from the dovetail Wing components of the mold by acid pickling and heat which breaks down the inventment.

The crown is then completed by inserting or forming a plastic or porcelain window veneer denoted generally by character 24 in FIG. 12 into the void 25 in the crown corresponding to the water-soluble insert which was leached out of the consolidated pattern before the wax moiety thereof was molded. The window veneer, illustrated in FIG. 12, is identical in size and shape to the water soluble pattern 13 of FIG. 3, possessing a corresponding window portion 26, dovetail wings 27 and 27', and rearward'ly extending, depending lip 28.

The cast gold crown may receive three types of veneers. One type is a pre-processed facing of plastic, or porcelain. A second type is to process the plastic into the window and a third method is to process porcelain into the window.

With regard to the use of a pre-processed plastic facing, it is sufiiciently resilient to permit adequate distortion of the dovetail wings 27 and the rearwardly extending, depending lip 28 to enable them to enter and mate with their corresponding undercut portions of the cavity 25.

To insert the veneer into the void provided in the crown 23, a thin layer of adhesive cement is applied to the entire rear surface of the veneer, and to the front surfaces of the dovetail wings 27. Similarly, a thin layer of cement is applied to the entire veneer cavity 25 in the metal crown 23. The cement is colored for correct shading of the veneer and to stop light transmission to gold.

The veneer is then forced into the cavity, insertion of the dovetail wings and the retaining lip being aided by temporary distortion of these resilient members and also by the lubricating qualities of the cement before it sets.

(It will be appreciated, of course, that the undercut nature of the dovetail wings 27 and 27' and the retaininglip 28 is somewhat emphasized in the drawings for the sake of clarity of illustration.) Similarly, a pre-processed porcelain facing may be cemented to form the completedcrown The product is then invested in a conventional mold. The crown with theplastic facing is then removed by breaking the plastic mold.

The application of porcelain facing into the window is basically similar. The porcelain in the form of a powcrown. There is no need for undercuts in the gold crown in this case since the porcelain is fused directly to the gold. The completed veneered crown, ready to be cemented to a tooth stump, is illustrated generally by character 29 in FIG. 13. It comprises two visible parts, the gold body 30 and the exposed front surface of the veneer 31. The

veneer is mechanically locked in place by means of the

dovetail wings

27 and 27 and depending lip 28 which, of course, are not visible in the finished crown29 illustrated in FIG. 13. i a

deris mixed with water, shaped to conform with the precarved window in the pre-shaped gold crown, and the porcelain is then cured while in place against the gold The instant veneer maybe prepared from any resilient I material otherwise suitable for the preparation of? dental veneers, the previously employed acrylic materials such as polymethylmethacry-late being particularly preferred. These veneers may be colored or pigmented in the usual manner, and may be provided in a spectrum of standard- -ized sizes, shades, and "shapes (within the scopeof the.

present invention).

"I Veneers in accordance with the present invention may be provided either separately orin combination with a water-soluble pre-formed pattern thereofleach size and shape of veneer being duplicated by'suoh apre-formed pattern. p

The pro-formed patterns are prepared asohd material which is soluble or dispersib-le in an aqueous solvent,

so as to permit the solvent to preferentially leach the preformed Window insert from consolidated or insert containing pattern of the final veneered crown. Preferm ably, the insert material is one which is substantially stable under ambient conditions, i.e., is not delrquescent or etflo-rescent, and which is soluble or disp-ersible in a cold aqueous solvent (room temperature or below) so as of tooth bodies may be provided which have an enlarged frontal Void suitable for receiving a variety of shapes and sizes of pre-formed water-soluble veneer insert patterns. A veneer pattern of the desired shape and size is applied to the frontal void of the wax pattern, and, to complete the wax pattern, it is then merely necessary to cover the dovetail wings and any remaining interstices with the necessary wax, smooth the added wax to contour, and then leach the water soluble insert from the consolidated pattern.

It will now be seen that the present invention encompasses a new concept for the preparation of veneered cast dentalxreplicas wherein there is provided, separately or in combination as a paired or matched set, a resilient dental veneer having undercut locking means extending therefrom (preferably on lateral extremities thereof) adapted to be embedded in and concealed and retained by a body portion of a tooth replica, and a water-soluble pattern or replica of the veneer member. .There is provided also a process wherein such a water-soluble pattern is employed in conjunction with Waxy material to form a pattern of a veneered dental product, and the water-soluble pattern of the veneer member of the product is leached from the waxy material to form a window-containing wax pattern which may be invested with molding material, eliminated from the mold, and reproduced in metal to form a metal body which is adapted to accept a resilient veneer having thesame size and shape as the pro-formed water-soluble pattern originally employed.

The same basic'process can be employed for manufacture of crowns or other similar structure to serve as abutment retainers for attachment of a bridge or pontic. As previously indicated, one method employed at the present time is to grind a slot in the crown in which is soldered a "female attachment which is fitted with a'rnale attach merit carrying the bridge or pontic. There are man'yobvious diificulties with such procedure which are obviated by the present process.

As part of this aspect of my invention, there is first prepared a waxed stump which could be similar to that in FIG. 2 but isusually on a posterior tooth. The watersoluble pro-formed pattern or insert is added thereto and is of any desired shape to form the type of slot, groove or opening desired. The pattern need not have dove- Y water-soluble pattern is sealed to the wax body by additails unless desired depending upon the type of attach,- ments to be employed for supporting the bridge. The

tional .wax forming the desired contour of the tooth surface. i

The water-soluble insert is then flushed away with an aqueous solvent and the resulting wax pattern with the pro-formed groove is invested and cast, resulting in'a to minimize detrimental action on the wax, e.g., solubliza-f tion or distortation thereof. Thus, the preformed pattern may be prepared from gelatin, water-soluble glue, polyvinyl alcohol, and the like. 1

Aq liedh s solvents suitable for use in accordance with the present invention are water, aqueous solutions ofwetting and surface active agents, dilute aqueous solutions of acids and bases, and aqueous solutions of organic solvents such as ethanol which are non-WaxdissolVing selective solvents. Distilled water is, however, the-preferred solvent. r

e.g., petroleum-derivedhigh molecular weight paraffins The process and products of the present invention may ,be employed in conjunction with the preparation of replicas of veneered teeth for a wide variety of purposessuch as crowns, pontics, bridges, and the like. 'For example, for the preparation of pontics, pre-formed wax patterns gold crown with the pre-formed opening. This procedure has been basically described in connection with FIGS. 4-11 above.

The female precision attachment may then be cemented or soldered in place for the subsequent attachment of the male abutment carrying the bridge or pontic. The groove will be made usually slightly larger so as to accommodate the cement or solder. This product is illustrated by FIGS. 14 and 15. In these figures, character 32 is the occlusal surface of a cast posterior crown which is the same. shape as the wax pattern. Character 33 refers to the groove, slot or window formed after dissolving out the water-soluble insert and 34 illustrates a typical female precision attachment which has been cemented or soldered in place. i

It is another embodiment of the present invention that the slot or groove can be made slightly smaller than or an exact replica of the female attachment so that no interproximal space remains. To insert the female precision attachment, the gold crown is heated to expand ment may be inserted readily and joined to the crown.

7 Upon attaining room temperature, the resulting product is the same as if the two materials had been fused. The advantages of this process are evident since the time and expense involved in soldering have been completely elimi nated.

Another major advantage of using my process of forming the abutment retainer is that the slot or groove which is preformed can be prepared with undercuts or dovetails, as described previously, using Water-soluble patterns having such features. In the prior methods used, dovetails could not be formed in the slots. As a result, my process permits the use of precision rests and is not limited to precision attachments.

While there has been disclosed and described that which is at present considered to be the preferred embodiment of the invention, it will be understood, of course, that many changes, modifications, and/or substitutions may be made therein without departing from the true scope of the invention as defined in the appended claims.

What is claimed is:

1. A process for the preparation of a crown for attachment to a pontic which comprises forming a preformed pattern composed of a normally solid water-soluble material on a portion of a mount formed of waxy material, said water soluble pattern when removed therefrom forming an opening to serve as means of attachment to said pontic, shaping said waxy material to form with the pre-formed water-soluble pattern a consolidated pattern of a crown having a desired contour of the tooth surface, leaching said water-soluble pre-formed portion away from said Waxy material with an aqueous solvent to form an opening therein, investing said Wax pattern in a mold, reproducing a metal replica of said wax pattern containing said opening, and recovering said metal replica in the form of a crown having said opening for attachment to a pontic.

2. A process in accordance with claim 1 wherein a female precision attachment to said pontic is inserted in said opening in said crown as a support for the pontic.

3. A dental veneer having integral multiple supporting and retaining means for engagement with the body portion of a dental crown which comprises locking means integral therewith and extending laterally and inwardly from two opposing edges thereof behind the forward face of said veneer, said locking means on each of said two edges comprising a recess wider at its base than at its opening and adapted to interlock with a corresponding projecting mating member attached to said crown body portion so as to conceal and retain said veneer looking means therein, :and said veneer having an integral depending lip extending rearwardly from an edge of said veneer between said lateral recess-containing edges for attachment to said crown body portion, said veneer being sufficiently resilient to permit engagement of said recesses and lip thereof with mating members in said crown body portion.

4. A dental veneer for engagement with the body portion of a dental crown which comprises locking means integral with said veneer and extending rearwardly behind the forward face of said veneer, said locking means comprising an undercut recess adapted to receive a corresponding undercut mating member attached to said crown body portion and interlock said veneer therewith so as to conceal and retain said veneer locking means therein, said veneer being resilient sufiiciently to permit engagement of said veener undercut locking means with said undercut crown mating member.

5. A dental veneer crown which comprises a shell crown having an opening on the frontal surface and a dental veneer covering said opening, said veneer having locking means integral therewith and extending laterally and inwardly from two opposing edges thereof, the forward surface of said locking means being recessed behind the front surface of the opening in said shell crown, said locking means on each of said two edges comprising an 8 undercut recess wider at its base portion than at its opening and interlocking with a corresponding projecting mating member Within said shell crown so as to conceal and retain said veener locking means therein, said veneer being sufliciently resilient to permit engagement of said recesses with said mating members in said shell crown.

6. A dental veneer crown which comprises a dental veneer on the frontal surface in engagement with the body portion of a dental crown, said veneer having integral locking means extending rearwardly behind the exposed front surface of said veneer, said locking means comprising an undercut recess in engagement with a corresponding undercut mating member attached to said crown body portion and interlocking said veneer therewith so as to conceal and retain said veneer locking means therein, said veneer being resilient to permit insertion of said veneer undercut locking means into engagement with said undercut crown mating member.

7. A dental veneer crown as set forth in claim 6 wherein said locking means is a dovetail.

8. A dental veneer crown as set forth in claim 6 wherein said locking means is a rearwardly extending, depending lip.

9. A dental veneer crown as set forth in claim 7 wherein the forward surface of said dovetail is recessed behind the exposed front surface of said veneer, said crown body portion having a window covered by said veneer and said dovetail locking means extending through said window and engaging the corresponding mating member in said crown therein.

10. A process which comprises forming a tooth-simulating pattern composed of a normally solid water-soluble material on a surface of a mount formed of water-insoluble waxy material, said water-soluble portion when removed therefrom forming an opening to serve as means for attachment of a veneer, said waxy material forming with said pre-formed water-soluble portion a consolidated pattern of a desired tooth, having said water-soluble pattern on a portion thereof, and leaching said water-soluble pattern away from said Waxy material with an aqueous solvent to form a pattern of the desired finished v tooth having an opening to serve as means for attachment replica which comprises super-imposing a pre-formed pattern composed of a normally solid water-soluble material on the frontal surface of a mount formed of waterinsoluble waxy material, said water-soluble pattern having the shape and perspective of a tooth facing and when removed therefrom forming a window, said water-soluble pattern having lock-forming means integral therewith for forming a locking means in said waxy material, embedding said lock-forming means in said waxy material, shaping said waxy material to form with said pro-formed water-soluble window pattern a consolidated pattern of a desired finished tooth having said water-soluble pattern as the front surface thereof, and leaching said watersoluble pre-forrned window pattern and the lock-forming means thereon away from said waxy material with an aqueous solvent to form a window-containing pattern of the desired finished tooth :and a locking means recessed therein for attachment of a veneered tooth replica.

12. A process for the preparation of a veneered tooth replica which comprises super-imposing a pre-formed pattern composed of a normally solid Water-soluble material on the frontal surface of a mount formed of water-insoluble waxy material, said water-soluble pattern having the shape and perspective of a tooth facing and when removed therefrom forming a window, said water-soluble pattern having lock-forming means integral therewith for forming a locking means in said waxy material, embedding said lock-forming means in said waxy material, shaping said waxy material to form with said pre-formed water-soluble window pattern a consolidated pattern of a desired finished tooth having said water-soluble pattern as the frontal surface thereof, leaching said water-soluble pro-formed window pattern and the lock-forming means thereon away from said waxy material with :an' aqueous solvent to form a window-containing pattern of the deposing a preformed pattern composed of a normally solid water-soluble material ,on the frontal surface of said waxy material, said water-soluble pattern having the shape and perspective of a tooth facing and whenremoved therefrom forming a window, said water-soluble pattern having undercut lock-forming means integral therewith and exwater-soluble pre-formedwindow pattern and undercutlocloformingmeans thereon away from said waxy material with an aqueous solvent to form a window-containing waxy patterniof the desired metal crown, and undercut locking means recessed therein for attachment of a veneer thereto, investing saidwindow-oontaining waxy pattern in a mold, reproducing a east metal replica of said windowcrown which comprises applying a water-insoluble wax to a die simulating a stump to be crowned, superimposing a preformed pattern composed of a water-soluble wax on the frontal surface of said wax covered die, said pattern having the shape and perspective of a tooth facing and when removed therefrom forming a window, said watersoluble pattern having dovetail lock-forming means integral therewith and extending laterally from two opposing edges thereof and also having an integral depending lip extending rearwardly from an edge thereof extending between said dovetail-carrying edges, said dovetails being window as a frontal surface thereof, leaching saidwaterrecessed with respect to the front surface of said window, embedding said li-p in said wax and applying additional wax to said waxed die to embed said dovetails therein, contouring said waxto form with said pattern a consolidated pattern of a desired finished crown having said soluble pattern including said lip and dovetails from said containing waxy pattern in said mold, recovering said I metal replica from said mold, and inserting, in the win' dow-containing metal replica, a resilient veneer having the same size and shape as the aforesaid pro-formed watersoluble pattern. Q a i 14. A process for the preparation of a veneered gold wax with water to form a window-containing wax pattern of the desired gold crown, said window-containing pattern having undercut lip and dovetail-mating members therein, investing sa-i-d window-containing wax pattern in a mold, reproducing a cast gold replica of said window-containing wax pattern in said mold, and inserting, in the windowcontai-ni-ng gold replica, a resilient plastic veneer having the same size and shape to the aforesaid dovetail and lipcarrying pre-formed water-soluble pattern, said resilient veneer being adapted to temporarily distort to permit insertion of the dovetails and lip thereon into engagement with the mating members therefor, cast in to said gold crown.

References Cited in the file of this patent UNITED STATES PATENTS 1,523,519 Gibbons Jan. 20, 1925 1,603,262 Alden Oct. 19, 1926 2,700,822 Infante Feb. 1, 1956 2,930,124 Pos Mar. 29, 1960 OTHER REFERENCES For-Cast, Veneer-Dental Survey, March 1935, page 8 (Buyers Guide).