US2302375A - Artificial tooth and method of making the same - Google Patents

Description

Nov. 11, 1942. s, YERSON 2,302,375

ARTIFICAL TOOTH AND METHOD OF MAKING THE SAME Filed March 15, 1940 2 Sheets-Sheet '1 Nov. 17, 1942. s. MYERSON 2,302,375

ARTIFIGAL TOOTH Ami METHOD OF MAKING THE SAME Filed March 15, 1940 2 Sheets-Sheet 2 Patented Nov. 17, 1942 ARTIFICIAL TOOTH AND METHOD OF MAKING THE SAME Simon Myerson, Brookline, Mass Application March 15, 1940, Serial No. 324,121

6 Claims.

This invention pertains to artificial teeth and relates more particularly to improvements designed to impart an appearance more closely simulating that of natural teeth than has heretofore been done, the present application being a continuation-in-part of my copending applications for Letters Patent Serial No. 78,674, filed May 8, 1936; Serial No. 104,039, filed October 5, 1936, now issued as Patent No. 2,202,712;- Serial No, 180,725, filed December 20, 1937, now issued as Patent No. 2,202,713 dated May 28, 1940; and Serial No. 191,218, filed February 18, 1938, respectively.

Attempts have previously been made by teeth manufacturers and dentists to make artificial teeth resemble natural teeth in appearance, but despite the most artistic carving and the application of stains and glaze by the dentist, the artificial tooth is readily distinguishable from the normal tooth, at least by experienced persons.

Apparently most previous experiments designed to improve the visual appearance of artificial teeth have been without due regard to the fact that when in use the tooth is viewed against the dark background afforded by the oral cavity, and that the effect of light striking the tooth and being partially reflected therefrom is greatly modified by the presence of this dark background. Failing to recognize'this fact, much of the prior experiment and practice has been concerned with the use of colored materials and the' application of stains or the like in the effort to obtain the peculiar shadowy ellect observed in natural teeth under varying light conditions, but whereas colored material or stain may be effective for the intended purpose under some light conditions they frequently fail utterly to give the desired results under different light conditions, it being well recognized that artificial teeth are particularlynoticeable as such at night when observed under artificial light.

While it is a matter of common knowledge that in a very large percentage of, natural teeth, the substantially transparent or at least translucent enamel layer not only covers the labial surface of the tooth,but forms in effect a cap at the incisal edge, and that in many instances at least this cap is of substantial depth so that it forms portions of both the labial and th lingual surfor". of 'h= too x a-d ex ends a su'zstantial distance downwardly beyond the relatively opaque body portion of the tooth, no one, so far as I am aware, has heretofore (his 1'; an impo tazit factor in respect to the optical appearance of the natural tooth. More 15. Natural teeth recognized the fact that.

over, in the natural tooth, the opaque body portion usually tapers inthickness as it approaches the opposition to the passage of light gradually di- 5 minishes to the point where it merges with the material of the transparent cap. Thus the darkness of the oral cavity is effective not only at the extreme incisal edge but also for a substantial distance (but with diminishing intensity) away from said edge, and. this I believe is responsible in large measure for the characteristic 7 appearance of natural teeth as contrasted with that of artificial teeth made in accordance with prior practice.

are not of uniform appearance nor are the incisal edge portions of natural teeth (consisting almost wholly of enamel) exactly uniform in color, thickness or texture. As a matter of fact, the labial surface, and in particular 0 the incisal portion of a natural tooth, usually has narrow, more or less parallel faint lines or stains extending substantially perpendicular to the incisal edge, or, in other words, extending lengthwise of the tooth. These narrow lines usually 5 result from the presence of fine cracks in the enamel.

In accordance with the present invention, I construct the artificial teeth as nearly as possible to simulate the construction of the natural teeth as respects the arrangement of the transparent enamel and the relatively opaque body portion, as above described. Thus I cause the body portion to taper downward but to terminate short of the incisal edge, and cause the enamel layer which covers the labial surface of the tooth to form in effect a cap in which the tapered end of the body portion is embedded and which forms the incisal edge and also the lateral edges of the tooth. Thus the transparent material is so -10 blended with the more opaque body material that the finished tooth has a fringe, including the incisal edge, which is preferably of substantially complete transparency, the tooth gradually becoming less transparent toward its mid-portionthe body and gingival portions being as opaque as may be desired.

I also construct the tooth or a tooth facing so that it may be manufactured in finished form and by mass production methods and so that when viewed against the dark background of the oral cavity, it exhibits narrow streaks or shadow lines closely simulating those of natural teeth, the streak-forming material being a permanent part of the tooth structure incorporated during manufacture.

incisal edge so that its effective I may also reproduce the effect often found in natural teeth, of an opaque light-colored area distinct from the surrounding portions of the tooth, by embedding in. the substance of the tooth a preformed insert of the desired contour so disposed in the mould that it lies close to the labial face of the tooth where it is visible through the enamel. This insert may be of any desired contour and, being of a lighter color than the body portion of the tooth, appears as a whitish irregular area when viewed from the front. By making this insert as a preformed, solid piece, danger of change in shape during the fusing of the tooth may be avoided.

It is common to fill cavities in natural teeth with porcelain fillings, and it has been observed that such fillings in natural teeth commonly .bleach during use so as to appear a little lighter than the surrounding material of the natural tooth. Moreover, such porcelain fillings do not always fit snugly, so that it is quite common to observe a stained effect at the junction of the filling with the body of the tooth. Furthermore, such fillings often appear to project slightly from the surface of the tooth itself, both at the labial face and at the incisal edge. In accordance with one aspect of the present invention it is proposed to make an artificial tooth in which the natural appearance is enhanced by giving the tooth an appearance closely simulating that of a natural tooth having a porcelain filling.

In order to obtain an even finer graduation and blending of light efl'ects, it is contemplated that a layer of material, of a transparency intermediate those of the body portion and incisal cap, may be interposed between the labial surface of the tapering part of the body portion and the transparent enamel layer.

The result of the improved construction is that when the tooth is in use and viewed against the dark oral cavity, the incisal portion of the tooth takes on a bluish shadowy appearance, closely simulating the natural tooth, such appearance varying with different light conditions and changes in perspective as it does in a natural tooth, so that teeth made in accordance with the present invention are ahnost undistinguishable from natural teeth even under th most trying light conditions, for example when viewed at nightby artificial light, and at the same time,

even though manufactured by mass production methods, possess the lack of uniformityof natural teeth, and if desired, imitate usual defects and repair work common to natural teeth.

Otherobjects and advantages of the present invention will be made manifest in the following more detailed description and by reference to the accompanying drawings, wherein:

Fig. 1 is a side elevation of a tooth, for example an anterior tooth, embodying the present invention;

Fig. 2 is a front or labial view of the.;tooth of Fig. 1; i

, Fig. 3 is a vertical section on the line 3-}; of

Fig. 3, but illustrating a modification of the structure of Fig. 3; r

Fig. 9 is a section similar to Fig. 8, but showing a further modification;

FigflO is a section sin iilar 1.015573, slime a" step in the manufacture of the tooth of Fig. 12.

With reference to the following description of the improved tooth structure, it may first be stated that the impro'ved tooth may be made in substantial accordance with usual methods employed in making artificial teeth, including the packing of suitable slip material into the cavities of complemental mould members; the closing of the mould members and subjecting them to pressure and heat; and the subsequent removal of the green teeth from the mould and the firing of the teeth at a temperature such as to harden, and to some extent at least, fuse the ceramic material of which the tooth is composed.

Referring to Figs. 1 to 5 of the drawings, which illustrate certain broad aspects of the invention,

the numeral l designates the body portion of a too h, such body portion being formed from a slip material designed to produce a body of a'substantial degree of opacity, it being understood that the slip material forming the body portion may be tinted as desired, so as accurately to simulate the color of the body portion of a natural tooth.

The body portion l preferably has embedded therein a suitable anchorage, for example, a metal part 2, which receives a pin 2 soldered or otherwise secured to the anchorage, and by means a of which the tooth may be mounted on a support,

for example, a plate or bridge.

. The body portion 1 has the gingival surface 3, the labial surface 4 and the lingual or pin-bearing surface 5 which extends down from the gingival surface to the usual plate-limiting boss or shoulder, and preferably tapers downwardly at its lower part to form a spur or tongue-like portion I, the lower end of which is substantially spaced from the incisal edge 9 of the finished tooth.

- As illustrated in Figs. 1 to 5, inclusive, the incisal portion of the tooth is formed as a generally triangular mass or cap 6 of substantial depth vertically and of enamel-like material, and comprising an upwardly extending labial coating or Fig. 4 is a transverse section on the line 44 of Fig. 3;

Fig.5 is a vertical section substantially on the line 5 5 of Fig. 3; Fig. 6 is a front elevation, to large scale, of an artificial tooth' of a preferred construction;

Fig. 7 is a fragmentary horizontal section, to

cusp having the forward surface I which merges smoothly with the surface 4 of the body portion, and a lingual coating or cusp having a rear surface 8 which extends upwardly and rearwardly to a point well above the lower end of the spur I of the body portion, as here shown to the platelir'niting boss or shoulder of the body portion. The triangular incisal mass or cap 6 also has lateral extensions 6* and 6'' (Figs. 2 and 5) which extend upwardly at opposite sides'of the spur I of the body portion, the edges of these extensions 6 and GP merging smoothly with the lateral edges I and I of the body portion.

From inspection of Figs. 3 and 4 it wlll be noted that the triangular incisal ,mass or cap. 6 has a downwardly directed cavity forming in efl'ect'a .socket forthe reception of thelower part of the body portion and the cap,

- tooth by spur I", the latter being embedded in and fused with the material forming the walls of such socket in the cap. However, as above noted, the spur l terminates at a substantial distance from the incisal edge 9 of the tooth, this distance, as illustrated, being two or more times the maximum horizontal thickness of the enamel at the labial side of the spur-i and preferably exceeding onethird or'even one-half of the distance between the labial surface 4 and the pin-bearing surface 5, that is to say the maximum horizontal thickness of the tooth at its upper portion.

The enamel-forming slip used in making the incisal mass or cap 6 is such that when the tooth is completed the cap transmits light much more readily than does the material of the body portion I. In fact, the cap is comp etely transparent, that is to say transparent to the extent that the outlines of an object may be seen through the substance of the tooth at the incisal portion of the latter, the tooth in this respect closely simulating a usual natural tooth.

When a tooth constructed as above described is arranged in normal position so as to be viewed against the dark background of the oral cavity,

light is reflected from the surface 4 of the body portion I, the latter being substantially opaque and usually of a light color, whereas light that strikes the labial surface 1 of the cap 5 passes quite freely through the cap material and is largely absorbed by the oral cavity, so that the cap portion appears as a dark fringe bordering the incisal portion of the tooth. The spur l of the body portion extends downwardly into the socket cavity above described, not only advantage in effecting a strong union between the but for the further that the gradually tapering spur I! results in a gradual screening of the light and a corresponding change in appearance from the relatively light upper portion of the tooth down toward the dark incisal edge portion, thus further simulating the appearance of the natural tooth in which the opacity gradually increases from the incisal edge toward the gingival surface and likewise inwardly from the lateral edges toward the center of the tooth. 7

While as illustrated in Fig. 3 the enamel forming the cap 6 terminates about midway the height of the tooth, it is contemplated that the enamel layer might be extended up even as far as the gingival .surface. Thus, as shown in Fig. 10, where the tooth is otherwise like that in Fig. 3, the material forming the cap 6 is shown as extending up in a thin layer 6* covering and protecting the labial face of the body portion l.

' With such an arrangement, if the enamel layer 6* be colorless but substantially transparent, the color of the body material will show through this enamel layer without substantial change except that the enamel layer imparts a bone-like or ivory luster to the entire labial surface of the tooth.

In accordance with the present invention it is also proposed to form the front or labial surface of the tooth so as closely to simulate a natural stains of a color or appearance which visually contrasts with that of the enamel and simulates the stains and streaks common innatural teeth. With this object in view, the present invention contemplates the use of elongate masses or inserts of a material less transparent than the enamel and which may be as deeply colored as desired, these inserts being so disposed as to ex in the upper part of the cap 6 as to obtain a mechanical the inclusion of narrow streaks andshapes.

overlies the labial surface of the body portion.

The intended effect of these inserts, at least at the translucent incisal portion of the tooth, is largely dependent upon the presence of a dark background (for example, the oral cavity or a proper masking for the supporting member of the tooth) against which to view the transparent incisal part of the tooth.

Preferably these streak simulating elements I3 take the form of elongate, triangular prisms, extending lengthwise of the tooth and desirably of slightly irregular contour so as better to simulate the irregular striations of the natural tooth. Preferably these inserts taper in widthupwardly and downwardly from their mid-portions as illustrated in Fig. 6. As already stated, these streak simulating elements l3 contrast visually in appearance with the enamel; for example, they may be of a contrasting color or merely different in -degree of opacity from the enamel; and one or more of such streak simulating elements may be embedded in the enamel of a tooth so as to become fused or otherwise permanently integrated with the enamel.

By making these streak simulating elements of wedge shape or triangular transverse section an indistinct or shadow effect is produced which much more closely simulates the natural tooth than would a streak simulating element of uniform transverse thickness.

In order to simulate the irregular, light-colored spots which sometimes appear in natural teeth, the present invention contemplates the interposition of bodies of material (indicated at 26 in Figs. 6, 7 and 11), usually of ceramic character, which are preferably preformed to the desired contour and size and which are inserted in the slip which forms the tooth during the moulding operation.

Preferably these inserted bodies are so disposed as to be sunk partly in the material forming the body of the tooth but to project forwardly into the enamel which forms the labial surface layer and are interfused with the body and enamel layers although substantially preserving their original Such inserts, when viewed through the enamel (if made of a material which is of a light color as compared with the body of the tooth) closely simulate th light-colored, dead appearing spots often observed in natural teeth.

In Figs. 6, 7, 11, 12 and 13 the tooth of the present invention 'is illustrated as provided with One or more simulated fillings, for instance simulations of a porcelain or synthetic porcelain filling such as arecustomarily employed in repairing natural teeth. These simulated fillings I5 are preferably of a, color or of .optical properties layer 1, the simulated filling lj may be of enamel somewhat more opaque than the main body of enamel. While it is preferred tdemploy this simulated filling in-a tooth such as hereinabove described, wherein the incisal portion is transparent, it is obvious that such simulated filling may be applied to any type of artificial tooth.

In making a tooth having a simulated filling such as that of Fig. 12, the green tooth may be shaped to receive the filling-simulating body by the use of a mould having a properly contoured the stain I1 is disposed only in the bottom of the groove, but for pronounced efiect it may cover the entire wall of the groove. After this elongate narrow' layer of stain has been placed in the groove, a coating l5 of enamel forming material, usually more'opaque or at least of different optical properties from the main layer of enamel, is put over the main layer of enamel, one edge l8 (Fig. 13) of said coating filling and being defined by the groove and its other margins gradually tapering and merging smoothly with the main body 6 of the enamel. S nce the edge portion l8 of this filling-simulating enamel l5 completely fills the balance of the groove not occupied by the stain I! (if the latter be used) and since the enamel is fused to the main body of enamel 6 when the tooth is fired, the stain I! is thereby completely housed in, hermetically sealed and protected from contact with the fluids of the mouth. Such simulated fillings ordinarily contrast but slightly with the main layer of enamel in appearance and usually are substantially flush with the latter or project very slightly. However, if desired, more pronounced effects may be'secured. as for instance by permitting the .incisal edge of the filling material to project slightly below the in"isal edge of the main body of enamel so that a-distinct notch appears at their junction.

In order to provide additional color effects, the arrangement of Fig. 8 may be'used. wherein the body portion of the tooth is indicated at 20 and the enamel cap at 2| (the latter having the labial surface 22, the lingual surface 23 and the incisal edge surface [9) and-there is interposed between the forwardly and upwardly extending part of the cap 2| and. the forward surface of the spur, a

layer 25 formed from slip material which may be of thesame general character as that used in the body portion or in the cap portion if de-' sired, but which is of. a different color or shade. This layer being interposed between the lower part ahd the body portion and thelabial portion of the cap, imparts its own coloration to this part of the tooth and is found useful-in obtaining some of the effects which have heretofore been accomplished but in a crude and unsatisfactory wayby staining.

As shownin Fig. 9, the arrangement of Fig. 8 may further be modified by extending the material 25 upwardly in a thin layer 25* overlying the body material, and covering this thin layer 25 with an upward extension 2| of the enamel which forms the cap 2|.

In Fig, 11 there is show'n a denture 26 having mounted thereon a series of teeth embodying the novel features hereinabove described, and indicating the natural appearance of such teeth when rnounted for use.

In the above description, when reference has been made to the upper" or lower part of the tooth, it is to be understood that these and similar directional terms are used merely for convenience in description and with reference to the drawings, and without limiting intent.

Obviously other modifications and equivalent arrangements may be employed, and it is to be understood that all such modifications, substitutions of material, etc. as fall ,within the scope of the appended claims, are to be regarded as apart of the present invention.

I claim:

'1.As an article of manufacture and sale, an artificial tooth complete and ready, when supplied to the dentist, to be incorporated, without unusual modification of structure in a denture, said tooth comprising a substantially opaque body portion and a coating of enamel fused to and overlying the incisal part at least of the labial surface of the body portion, an elongate narrow layer of stain, optically distinct'from the enamel which forms said coating, located between the lingual and labial surfaces of said coating, and a body of enamel fused to said enamel coating and completely covering the stain thereby protecting the stain from contact with the fluids of the mouth.

2. Asan article of manufacture and sale, an

' artificial tooth complete and ready to be inportion of relatively corporated without unusual modification of structure, in a denture, said tooth being of the kind in which a substantially opaque body has a coating of transparent enamel fused to its labial face, said tooth being characterized in having fillingsimulating enamel, more opaque than the enamel coating and of small superficial extent as compared with the labial area of the tooth, fused to the enamel coating and constituting a portion of the outer surface of the tooth,-and means operative to emphasize the line of junction of said filling-simulating material with the enamel coatmg.

3. As an article of manufacture and sale, an artificial tooth complete and ready, when supplied to the dentist, to be incorporated, without unusual modification of structure in a denture, said tooth comprising a substantially opaque body and a main layer of transparent enamel covering the labial surface of the body, a simulated filling consisting of enamel less transparentthan said main layer of enamel and of an area which is small as compared with the entire labial area of the tooth, the simulated filling having an edge which is directed rearwardly and which is seated in a cavity in the labial side of the tooth, and a dark staining substance .within said cavity and covered by the filling-simulating enamel, the filling-simulating enamel being fused to the main body of enamel and exposed at the outer surface of the tooth and having a contour such as to simulate a filling in a natural tooth.

4. An artificial tooth of the kind having a body opaque ceramic material which constitutes the 1 and enamel forming the incisal edge of the tooth,

characterized in that the edge-forming enamel is an integral part of a mass of substantially major part of the tooth colorless enamel which is relatively more transparent than the material of the body of the tooth and which has an upward extension overlying the lower part at least of the labial surface of the body portion, said edge-forming enamel extending vertically down below the lower end of the body portion to a distance which is at least onethlrd of the maximum horizontal distance between the labial and lingual surfaces of the tooth and acting, when the tooth is viewed against the background of the oral cavity, to impart a dark appearance to the lower portion of the tooth, and a simulated filling of small superficial area as compared with the entire labial area of the tooth, said filling consisting of enamel of d'iTerent optical properties from said incisal enamel, fusedto said upward extension,

5. An artificial tooth comprising a body. portion of relatively opaque material which constitutes the major part of the tooth and a body of transparent enamel forming the incisal edge portion of the tooth, characterized in that said edge-forming enamel is of such a degree of transparency as to permit the outline of an object to be seen through the substance of the tooth at its incisal portion, the vertical depth of said edge-forming enamel, between the lowest point of the body portion and the incisal edge of the tooth, exceeding one-third the maximum distance between the labial and lingual surfaces of the tooth whereby, when the tooth is viewed against the darkness of the oral cavity, a sub stantial area, adjacent to the incisal edge, appears darker than the gingival portion of the tooth, and a simulated filling of small superficial area as compared with the entire labial area of the tooth, said filling consisting of material of less transparency than the body of enamel which constitutes the incisal portion of the tooth and being fused to said incisal body of enamel.

6. An artificial tooth comprising a body portion of relatively opaque material which constitutes the major part of the tooth and an incisal mass of material which is of such a degree of transparency as to permit the outline of an objectv to be seen through the incisal portion of the tooth, said incisal mass terminating in an incisal SIMON MYERSON.

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