US2300305A - Artificial tooth - Google Patents

Description

ocrn 27, 1942. s MYERs-N 'l 2,300,305

ARTIFIGIAL TOOTH Qriginal Filed Harsh 15, 1940 Patentedv ocr. 27, 1942 Y 2,300,305 ARTIFICIAL TOTH Simon Myerson, Brookline, Mass.

Original application March 15, 1940, Serial No.

324,127. Divided and this application September 27, 1941, Serial No. 412,574v

11 Claims. (Cl. 32-8) This invention pertains to articial teeth and l relates more particularly to improvements designed to impart an appearance more closely Y simulating that of natural teeth than has heretofore been done, the present application being a division of my copending application Serial No. 324,127, led March 15, 1940.

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 articial tooth is readily distinguishable from the normal tooth, at least by experienced persons.

Apparently most previous experiments designedto 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 hasbeen concerned with the use of colored materials and the application of stains or the like in the effort to obtain the Ipeculiar shadowy effec't observed in natural teeth under'varying light conditions, but whereas colored material or stain may be effective for the intended purpose under some A light conditions they frequently fail utterly to Vit-'vforms portions of both the labial and lingual surface of the tooth and Vextends aV substantial material of the transparent cap.`v Thus the darkness of theoral 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 appearance of natural teeth as contrasted with that of articial teeth made in accordance with prior practice.

The principal object of the present invention -is to provide artificial teeth which as nearly as possible simulate theA appearance of natural attained by the novel arrangement of the transparent' enamel and the relatively opaque body portion, as above described. VTo 'this end 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 merge with .an incisal mass whichreceives and is fused with the tapered en d of the body portion and which forms the incisal edge and also the lateral edgesl of the tooth. The transparent material is so blended with the more opaque body material that the finished tooth has a margin, including the incisal edge, which is preferably of substantially complete transparency, that is to say, it so freely admits the passage of light that objects may be seen with well defined outlines through the substance of the tooth at its incisal portion, the body and gingival portions being as opaque as may be de.- sired.

' I also construct the'tooth oi' a tooth facing so that it may be manufactured in finished form and by mass production methods.

The result of the improved construction is lthat when the tooth is in use and viewed againstthe dark oral cavity, the incisal portion of, the tooth appears to have a dark bluish shadowy fringe, closely simulating the natural tooth, such appearance varying withdifrerentught condamnant.

, changes in perspective as it does in 'a natural distance downwardly beyond the relativelyA opaque body portion ofthe tooth, no'one, so

far as I am aware, has heretofore recognized 'l the fact that this is an important factor in respect to the optical appearance ofthe natural tooth. Moreover, in the natural tooth, the opaque body portion usually tapers in thickness fective forward reflection of light gradually di- Aduction methods, possess the lack of uniformity of natural teeth. Y

Other objects and `advantages of the present 4invention will be made manifest in the following inore detailed description and by reference to minishes to the point where it merges with the the accompanying drawings, vvherinrr` Fig. 1 is a side elevation of a tooth, for example an anterior tooth, embodying the present invention; e

, Fig. 2 is afront or labial view of the tooth of Fig. 3 is a vertical section on the line 3-3 of Fig. 2;

Fig. 4 is a transverse section on the line 4 4 of Fig.,3; f

Fig. 5 is a vertical section substantially on the line 5-5 of Fig. 3; and l Fig. 6 is a section similar to Fig. 3, showing a still further modification.

With reference to the following description of the improved tooth structure, it may first be stated that the improved tooth may be made in substantial accordance with usual methods employed in making .artificial teeth, including the packing of suitable plastic slip material into the cavities ofcomplemental 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 (assuming that they are of ceramic material) at a temperature such as to harden, and to some extent at least, fuse the material of which the tooth is composed.

While as above pointed out it is'the principal object of the invention to provide artificial teeth which, when in use, are substantially indistinguishable in appearance from. natural teeth, it is,

of course, obvious that teeth made b'y a moulding overlying and being fused to the labial surface of the body portion.

Inspection of Fig. 3 shows that the surface or .zone of contactI between the forward, upwardly directed cusp of enamel and the labial surface of the body portion. gradually recedes from said labial surface I of the body portion concomitantly with the approach of said contact surface or zone toward the incisal edge. In other words, the frontftorear thickness of the cusp increases downwardly, and this gradual increase in thickness of enamel, together with the downward and rearward slope of the labial surface of the spur I, results in a progressive diminution of the amount of incident light which is reected forwardly from said labial surface of the body portion (including the spur Ia) so that the color tone imparted by the body material to thetooth becomes less and less pronounced as said horizontal plane is approached.

As illustrated in Fig. 3, a secondv or rear extension or cusp, integral with the enamel mass,

process are not natural teeth, either in respect l to'the material of which they are constructed or in actual internal structure; nor are they subject to decay, disease or pain;

Referring toFigs. 1 to 5 of the drawing, which illustrate certain broad aspects of the invention, the numeral I designates the body portion of a tooth, suchrbodyportion 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 I` 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 of which the tooth may be mounted on a support, for example, a plate or bridge.

The body portion I has the gingival surface 3,

the labial surface 4 and the lingual or pin-bearing surface 5, which extends down from the girigival surface to the-usual plate-limiting boss or shoulders 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 ofthe finished tooth. Y

Below the body portion is an incisal mass 6 of enamel. The lower margin of this mass is shaped to form the incisal edge 9 which is of small radius (in vertical section) similar to that of the natural tooth. The incisal edge is vertically spaced from the horizontal plane of the'lowestpart of the body portion across the entire width of the tooth, and the incisal mass tapers downwardly in front-to-rear thickness (Fig. 3) from said plane.v The incisal7 mass has an integral, forwardportion, extending upwardly) above said horizontal plane.' said upward extension being i diere shownnasgtapering (as the toothis viewed in vertical mid section, Fig. 3)toform a cusp and 'surface of the body portion.

extends upwardly from said horizontal plane so as to overlie and is fused with the Alower lingual Said rear cusp preferably extends up substantially to the usual plate-limiting boss or shoulder S of the tooth.

The exposed rear surfaces of the enamel massproper. and its rear cusp merge smoothly, and collectively form the concave lingual surface 8 of the tooth, while the exposed forward surface of the enamel mass proper and the forward cusp merge smoothly, and collectively form the lower portion at least of the convex labial surface 1 of the tooth.

The incisal mass 6 also comprises integral lateral extensions 62. and 6b (Figs. 2 and 5) which extend upwardly at opposite sides of the spur I* of the body portion, the edgesof these extensions SLand 6b merging smoothly with the lateral edges Im and In of the body portion. Thus, as herein specifically illustrated (Figs. 3 and 4), the incisal massjform's'an inverted cap or crown having a downwardly directed cavity constituting in effect a socket for the reception of the spur I, the

'latter being embedded in and fused with the material forming the walls of such socket.

As here shown the spur I* terminates at a substantial distance above the incisal edge 9 of the tooth. This distance is such as to permit light to pass so freely'through the entire widthof'the incisal portion of the tooth (except as such pass'- age may be locally obstructed by stria or other defect-simulating elements embedded in the enamel mass)- Vas to impart to the tooth the appearance when in use of having a dark shadowy fringe of progressively deepening tone, thereby to simulate natural teeth, as more fully described hereinafter. This distance is at least approxi'- mately one-third the horizontal distance between the labial surface 4 andthepingbearing surface 5ftlatist6'say atleast approximately one-third of the maximum front-to-rear .horizontal thickness of the tooth at its upper portion. Since such front-to-rear thickness in usual and normal types ofcommercial articial teeth is commonly in the neighborhood of three-sixteenths of an inch (at the upper portion of the tooth) the depth of the incisal mass in accordance with the ratio above suggested would usually be of the order of onesixteenth of an inch or more. y

When, in the vlappended claims, the distance between the lower end of the spur I* and theincisalv edge is referred to as a "substantial distance, the word substantial is hereby intended and is to be construed as indicative of a distance such as defined by the above specified dimensional relationships. The enamel-forming slip used in making the incisal cap 6 is such that when the tooth is completed the ca'p transmits light much more readily than'does the material of the body portion I. In fact', the cap is 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 against the dark background of the oral cavity,

light is reflected forwardly from the labial surface 4 of the body portion I, the latter being substantially opaque and usually of alight color,

.of the cap 6 as above described, not only to obtain a mechanical advantage in effecting a strong union between the body portion and the cap, but

for the further reason that the gradually taperl ing spur Ia with its forwardly convex labial surface results in a gradual lessening of the -amount of light which is reected forwardly with a corresponding change in appearance froml the relatively light appearing/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.

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. 6, 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 BX covering and protecting the labial face of the body portion I. With such an arrangement, if the enamel layer 6X 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.

As disclosed in my Patent N o. 2,202,713 issued May 28, 1941, the tooth may, if desired, be constructed so as further to simulate a natural tooth by the inclusion of narrow streaks or areas of a color or appearance which visually contrasts with that of the enamel and simulates the stains, dead spots, or striae common in natural teeth. l

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 Iarrangements may be employed, and it is to be understood that all such modifications, substitutions of material, etc., as fall within the scope o f` the appended claims, are to be regarded as a part of the present invention.

incisal portion, said mass of enamel having an i upward extension overlying the lower part at least of the labial surface of the body portion, said mass of transparent enamel extending ver tically down below the lowest point of the body portion to a distance which at least approximates one-third of the maximum horizontal distance between the labial and lingual surfaces of that part of the tooth which is above the plate-limiting shoulder, thereby imparting a dark appearance to the incisal portion of the tooth when the tooth is viewed against the dark background of the `oral cavity.

2. An artificial tooth having a downwardly and rearwardly sloping gingival surface, a pin-bearing surface and a plate-limiting shoulder, said tooth comprising a body portion of relatively opaque material and being v'provided with pins for attaching the tooth to a support, and an incisal portion of material of such transparency that the outline of an object may be seen through the substance of the tooth at said incisal portion,

said portions meeting and merging in a contactJ zone whose nearest approach to the incisal edge is at a distance from the 'latter which at least approximates one-third the maximum horizontal distance between the labial and pin-bearing surfaces of the tooth, said contact zone gradually receding from the labial face and from the lateral .edges of the tooth as it approaches the incisal edge whereby the tooth has a relatively transparent light-transmitting fringe of substantial depth. the transparency of which gradually diminishes inwardly away from said ed'ges.

3. A moulded artificial tooth constituting an article of manufacture and sale formed from mouldable material and `devoid of roots, pulpupwardly above said horizontal plane and overlying and being fused to the labial surface of the lower part at least ofthe body portion, characlferized in that the enamelmass is of substantially complete transparency and whose minimum depth below said horizontal plane at least approximates one-third of the maximum front-torear thickness of the upper portion of the tooth whereby a dark shadowy appearance is imparted toxthe tooth when the latter the darkness of the oral cavit 4. As an article of manufacture, a moulded ,is viewed against artificial tooth including a -body p ortion of relayfront-to-rear thickness pering downwardly from said lplane such transparency that the outline of an objectl tively opaque material and a mass of substantially transparent enamel below the body portion, said mass of enamel tapering downwardly in from the horizontal plane of the lowest part of the body portion, ,the lower margin of said enamel mass being shaped to form an incisal edge of small radius, said edge being spaced vertically a substantial distance below said plane across the entire width of the tooth, said enamel mass having integral portions extendingA upwardly above said horizontal plane at the front and rear sides respectively of said extensions overlying and being fused to the lower portions at least of the labial land lingual surfaces of the body portion, the exposed surfaces of said upward extensions merging smoothly with the front and rear surfaces of the enamel mass proper thus providing smoothly curved convex and concave labial and lingual tooth surfaces, said latter surfaces converging toward the incisal edge, the depth of the incisal mass from said horizontal plane to the incisal edge exceeding the thickness of the enamel at any point above said horizontal plane as measured from the outer sur-'- face of the enamel in a direction normal to the surface of the body portion, its depth and trans.

parency being such as to impart a dark shadowy appearance to the incisal portion of the tooth when the latter is viewed against the dark background of the oral cavity.

5. As an article of manufacture and sale, an artificial tooth, moulded from plastic material and-devoid oflroots, pulp-cavity or nerves, said tooth comprising a body portion which is relatively opaque and an incisal portion of substantially transparent material, said portions being so const'ructed and arranged that at the vertical mid-plane of the tooth 'said portions meet in a rearwardly and downwardly sloping line of contact whose distance from the labial 'surface of the tooth progressively increases and whose lowest point is a substantial distance above the incisal edge of the tooth, the incisal. -portion being thickest horizontally in the horizontal plane of the lower end of said line of contact and tapering downwardly from said horizontal plane, said taincisal portion being so transparent that the outlines of an object may be observed through its substance and the minimum depth of said transparent incisal mass below the lowest part ofthe body portion being such that when the tooth isviewed against the dark background of the.oral cavity it appears to have a dark shadowy incisal fringe across its entire width.

6. As an article of manufacture and sale, an artificial tooth, formed from mouldable material,

devoid of' roots, pulp-cavity or nerves", said tooth comprising a body portion which 'is relatively opaque and an enamel portion of substantially transparent material, the enamel forming ,the major portion at least of the labial face of the tooth and constituting the incisal edge of the tooth across the entire width of the latter, the labial surface and 'lateral edges of said opaque body kportion progressively receding from the exposed labial face and from the exposed lateral edges respectively of the tooth as they approach the incisal edge," the enamel portion comprising an incisal mass 'which is horizontally thickest yfrom front to rear inthe plane of the lowest point of the body portion and which tapers and which is of may be seen through it, the lowest point of the body portion being spaced such a substantial distance from the incisal edge across the entire width of the tooth as to permit the transmission of light through said incisal mass from front to the tooth,

rear unobscured by any part of said body portion, thereby imparting a dark shadowy appearance to the incisal portion of the tooth whenit is viewed against a dark background.

'1. An artiiicial tooth comprising a body portion of relatively opaque material and constituting the major part .of the tooth, and an incisal portion of a relatively transparent enamel, the lower part of the body portion tapering downwardly, at least in front-to-rear section, and the incisal portion terminating at the incisal edge, characterized in that the incisal portion is substantially sagittate` in vertical front-to-rear section, having upper labial and lingual'cusps, the incisal portion extending below the lower end of the body portion to a distance substantially exceeding the maximum front-to-rear thickness of its labial cusp, whereby when the tooth is viewed against the background of the oral cavity its incisal portion appears of gradually increasing darkness toward its incisal edge. I

8. An'artiiicial tooth comprising a body portion of relatively .opaque material which constitutes the major part of the tooth and which terminates short of the incisal edge ofthe tooth, a layer of material of a different degree ofopacity overlying that part of the labial surface of the body portion which is remote from the gingiyal surface of the tooth, and a cap of relatively transparent material-which embraceslthe lower end of the body portion with its overlying layer of material, the cap terminating in an incisal edge and having labial and lingual faces which' merge at said edge, the `cap including a labial portion which extends upwardly a substantial tion of the cap whereby, when the tooth is viewed against the dark background of the oral cavity, the lower part of the tooth appears darker than the gingival portion of the tooth.

- 9. An artificial tooth of the kind having a body portion of relatively opaque ceramic material which constitutes the major part of the tooth 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 colorless enamel which is relatively more transparent than the material of the body of the tooth and whichhas an upward extension overlying the lower part atleast of the labial surface of. the body portion,` said mass of enamel extending vertically down below the lowest point of the body portion to a distance exceeding one-third of the maximum horizontal distance between the labial and lingual surfaces of the tooth, thereby imparting a dark appearance to the incisal portion of the tooth when the tooth is viewed against the dark background of the oral cavity.

10. An artificial tooth having a body portion of relatively opaque material, said body portion being provided with means for attaching the tooth to a support', and an incisal portion of relatively transparent material, said portions meeting'and merging in a contact zone whose nearest approach-to the incisal edge is at a distance from the latter exceeding one-third the maximum horizontal distance between the labial and lingual surfaces of the tooth, said contact zone gradually receding from the labial face and from the lateral edges of the tooth while concomitantly approaching the incisal edge whereby the tooth has a relatively transparent lighttransmitting fringe of substantial depth, the transparency of which gradually diminishes inwardly away from said edges.

11. An articial tooth having a body portion of relatively opaque material which constitutes the major part of the tooth and a mass of relatively transparent enamel which forms the incisal edge, the body portion tapering downwardly to form a spur whose lcwer end is substantially spaced from the incisal edge of the finished tooth,

the mass of enamel having a socket cavity in which the spur of the body portion is seated and a layer of ceramic material having a diierent visual appearance from that of the body of the tooth disposed against the labial surface of said spur, said -layer having a thin upwardly directed extension overlying the upper part of the body portion of the tooth and extending substantially to the gingival surface, the mass. of enamel which forms the incisal'edge also having a thin upwardly directed extension which overlies the extension of the ceramic layer and which also terminates substantially at the gingival surface of the tooth.

SIMON MYERSON.

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