US3218711A - Artificial teeth - Google Patents

Description

Nov. 23, 1965 B. CONNAN 3,213,711

ARTIFICIAL TEETH Filed July 17, 1962 INVEN TOR. GEORGE fieuci Con NAN United States Patent 3,218,711 ARTIFHCIAL TEETH George Bruce Connan, Preston, Victoria, Australia, as-

signor to Dentsply (Australia) Proprietary Limited, Victoria, Australia, a corporation of Australia Filed July 17, 1962, Ser. No. 210,595 5 Claims. (Cl. 32-8) This invention relates to artificial teeth and their manufacture. It is directed particularly to the production of artificial teeth which simulate natural human teeth and are to be used in intra-oral restorative devices.

Natural teeth comprise essentially a dentine core which is surrounded by a layer of tooth enamel. Observation discloses that natural teeth vary considerably in structure due to variations in the degree of opacity of the tooth, diminishing toward the incisal and marginal edges, and to irregularities in formation. It is these variations and irregularities which, to a certain extent, impart the natural appearanc to natural teeth. Developments in the art of manufacture of artificial teeth have been, from the cosmetic point of view, directed for many years toward the reproduction of artificial teeth or" the characteristics and irregularities in appearance 'of artificial teeth.

One of the most important advances in this direction Was the production 'of two-part teeth, molded from synthetic resinous material such as methyl methacrylate, in which there was provided a body of opaque material, which simulated the dentine of natural teeth, and a partly opaque, partly translucent veneer on the front or labial surface of the teeth, which simulated the enamel. One process for the production of such teeth is described in the specification of Australian Patent No. 119,646. In that process the enamel part is formed and cured then the dentine part is formed and the two parts brought together and given a final curing to unite the two parts. In another process the two parts are formed together and only one curing is carried out. Production of teeth by these processes enabled manufacturers more readily to simulate the gradation in opacity of natural teeth from relatively translucent incisal and marginal edges to a substantially opaque body.

Further developments have led to the reproduction of various effects to simulate the irregularity of natural teeth. Teeth have been produced with irregular labial and incisal surfaces and vertically extending striations and other special effects have been induced to reproduce corresponding effects in natural teeth. Striations have been produced by a variety of means including, in the case where the tooth is formed by the two-part method, the formation of an irregular interface between the enamel material and the dentine material. In other cases, columns or blades of relatively more opaque ma- .terial have been inserted in the teeth during manufacture.

These columns or blades extend upwardly from the incisal edge and have the effect of producing relatively darker or more opaque vertically extending areas simulating similar occurrences in natural teeth.

Other varying effects have been produced by introducing materials of contrasting shades into the tooth structure, at the boundary between the dentine material and the enamel material to produce areas of light and dark, so as to'attempt to produce de-calcified simulation effects. It has also been attempted to reproduce the pearly appearance of good natural teeth by the use of pearlescent "ice pigments dispersed generally throughout the enamel and dentine materials, but these attempts have met with only very limited success, especially in regard to producing life-like effects.

While all of these advances have resulted in the production of artificial teeth which extend more and more toward the apearance of natural teeth, one almost indefinable property of natural teeth has so far eluded the copyist. So far, no artificial tooth has been produced which will simulat the live appearance of a good natural tooth. This invention has as its principal object to capture that appearance of life and present it in an artificial tooth.

Our close study of carefully sectioned and preserved natural teeth has disclosed the existence of definite light reflection from the many minute tubules which radiate out from the core of the tooth through the dentine and enamel toward the outer surfaces of the tooth. We have observed that those tubules which are angled to the direction of incident light, when viewed from a suitabel position, present partly reflective high spots which, in good natural teeth, appear through the enamel layer as gently shimmering pearlescent areas disposed particularly adjacent the incisal edge of the labial surfac of the teeth. It is this phenomenon which, we believe, gives a good natural tooth its live appearance. Thus far, however, it has not been possible to reproduce in artificial teeth the means of natural teeth which produce such pearlescence.

The basic object of this invention, therefore, is to provide these pearlescent-appearing areas in artificial teeth by arranging in an artificial tooth a partly reflective layer or seprated reflective areas, which are preferably of an uneven nature. Best results have so far been obtained by including a partly reflective, partly translucent band-like layer in a restricted or localized area or areas located preferably in the incisal third of the tooth and adjacent the labial or buccal surfaces. The layer has been successfully produced by the use of pearlescent or pearl-like pigment applied, in the case of a two-part tooth, at the interface between the enamel material and the mor highly pigmented dentine material.

Details of the foregoing objects and of the invention, as Well as other objects thereof, are set forth in the following specification and illustrated in the accompanying drawing forming a part thereof.

In the drawing:

FIG. 1 is a front elevation of an exemplary artificial tooth embodying the principles of the present invention.

FIG. 2 is a vertical sectional view of said exemplary tooth as seen on the line 22 of FIG. 1.

FIG. 3 is a transverse sectional view of said exemplary tooth as seen on the line 33 of FIG. 1.

FIG. 4 is a view similar to FIG. 1,, but representing an exemplary appearance of an artificial tooth embodying the invention as viewed from the front or labial surface thereof.

The invention may be readily practiced in the production of two-part dentine-enamel material teeth by utilizing processes such as that described in prior Australian Patent No. 119,646. Using that process, the enamel part 10 of the exemplary artificial anterior tooth 12 preferably is first formed in the mold and then, while the enamel part 10 is still in the mold, a small amount of pearlescent pigment, such as a thin band 14 thereof, is applied toselected areas of the preferably uneven interface surface of the enamel which will mate with the dentine or body portion 16 of the tooth 12. This band is located preferably in the socalled incisal third of the tooth which is spaced upward from the incisal edge or occlusal surface and more extensively spaced downward from the gingival end 17 of the tooth. The pearlescent pigment forms a multitude of plane reflective surfaces to produce a mirror-like effect. As best seen in FIG. 3, the interface 18 of the enamel part 10 of the tooth is not a flat plane, or even a regularly curved surface in the preferred construction. Rather, it is a series of connected irregular curves, the axes of which are substantially parallel to the major axis of the tooth.

The advantage of such an irregular surface is that the reflection of light through the irregular shape of the enamel part, or, rather, the enamel-simulating part, of the tooth produces a much more life-like result to the observer. In regard to the present invention, such irregular surface 18 is especially advantageous in that the trans lucence of the enamel part permits light to be reflected from and also penetrate the band 14 or pearlescent pigment at different locations, depending upon the line of sight of the observer relative to the tooth. Typical lines of sight are represented by the arrows A, B, and C in FIG. 3 and, from these, one readily can visualize the possible varigated pattern effects which can be observed by a viewer. Thus, the desirable shimmering effect characteristic of normal pearlescence in an oyster shell, mother of pearl, and similar substances, is apparent to the viewer and is of a type that occurs in most natural, healthy teeth at substantially the same location. Hence, the aforementioned life characteristic is produced in artificial teeth by the present invention.

The pearlescent material may be pigments which are generally typified as occurring or growing naturally in plate or plane form. One commercial example is derived from fish scales and is available in two forms; platelets, which is the preferred form for use in accordance with this invention, and needles or fish paste, which gives a lesser optical effect. So-called pearl pigments may also be derived from oyster shell lining or other semi-translucent, semi-reflective materials which lend themselves, naturally or otherwise, to partial reflection of incident light without excessive scattering and diffusion. Suitable artificial pearl pigment'material is available and has been used successfully in tooth products made in accordance with the invention. These, generally, are lead salts of fatty acids and are flat, plate-like crystals in a suitable liquid or paste vehicle to render the pigment capable of ready application, preferably in the form of a band, to the desired tooth part by brushing, spraying, or the like. Spraying is highly effective to apply the pearlescent pigment material by masking those surface portions of the tooth part upon which no pigment is desired, to produce band 14 shown in FIG. 1, wherein it will be seen that preferably said band extends from one side of the tooth to the other in a mesialdistal direction.

The pigment may be suspended in a resin monomer of the material from which the tooth is constructed, methyl methacrylate, for example, or in a polymer which has been pigmented with the material in powder form. Such suspension may be applied by a brushing technique, for example, by depositing a drop from a looped wire. The pigment may also be applied in dry powder form and, if desired, subsequently wetted with a fine monomer spray. Where the pigment is applied in suspension, the viscosity of the suspension should be adjusted so that the plane surfaces of the pigment particles assume a preferred orientation in the plane of the layer.

After the pigment is applied to the interface of the premolded enamel part 10, the dentine or body part 16 of the tooth is formed suitably by molding and is integrally bonded to the enamel part 10, in accordance with conventional practice. The pearlescent layer thereby is incorporated into the tooth at the deutine-enamel interface. The irregular nature of such interface produces even more natural effects than if a relatively smooth surface were formed, such interface irregularity being preferably in both the incisal-gingival direction and the mesial-distal direction, and produces a shimmering effect such as FIG. 4 depicts.

The pearlescent effect of this invention possibly can be achieved otherwise than by the use of the material described above as pearlescent pigments. Any pigment or material which will provide a multitude of tiny reflective areas to produce a partly reflective and partly translucent effect may be used. Such effect, for example, is similar to that produced by a very thin silver plate or partial mirror-silvering. It is, of course, important above all to use a pigment material which will not be detrimental to the tooth structure and which is light-stable. It has been found, for example, that certain pigments of bismuth oxychloride are not suitable since they turn black when exposed to ultraviolet light.

Experimental teeth produced by the process described above have been found to be most attractive and possess a marked appearance of life.

While the invention has been described and illustrated in its several preferred embodiments, it should be understood that the invention is not to be limited to the precise details herein illustrated and described, since the same may be carried out in other ways falling within the scope of the invention as claimed.

I claim:

1. An artificial tooth formed from two parts comprising a relatively opaque inner body part and an outer translucent enamel-simulating part having complementary interface surfaces and connected together, said tooth having restricted area adjacent the incisal edge or occlusal surface which is visible through said outer translucent part on the labial surface of the tooth, said restricted area comprising a substantially continuous band of pearlescent material interposed between the interface surfaces of said connected parts and extending transversely across the body part of said tooth for substantially the full width thereof and positioned closer to the incisal edge or occlusal surface than it is to the gingival end of the tooth, the width of said band being substantially less than half the length of said tooth, and said material being semi-translucent and semi-reflective and simulating the pearlescent effect of a natural tooth when light is reflected thereby due to said material only partially reflecting incident light without excessive scattering and diffusion thereof.

2. The artificial tooth according to claim 1 in which the complementary interface surfaces of said connected tooth parts are uneven and said band of pearlescent material being relatively thin and shaped by said uneven interface surfaces, whereby said band of material is similarly uneven.

3. The artificial tooth according to claim 1 in which said inner and outer parts thereof comprise synthetic resin and said pearlescent material initially being dispersed in a resin monomer compatible with the resins of said tooth parts and suitable to facilitate the deposition of said pearlescent material on said interface surfaces prior to said material being bonded to said resin parts of said tooth.

4. The artificial tooth according to claim 1 in which said layer of pearlescent material comprises small platelike particles of pearlescent material, said particles being substantially parallel to the interface surfaces of the parts of said tooth against which they are positioned.

5. An artificial tooth comprising two parts connected together and having a restricted area adjacent the incisal edge or occlusal surface and visible on the labial surface thereof, said restricted area comprising a layer of pearlescent material interposed between said connected parts and selected from the class consisting of fish scales, the lining of oyster shells, and the lead salts of fatty acids, whereby said layer of material simulates 5 6 the pearlescent effect of a natural tooth when light is FOREIGN PATENTS reflected from said 00111. 99309 1944 France.

References Cited by the Examiner RICHARD A. GAUDET, Primary Examiner.

UNITED STATES PATENTS 5 ROBERT E. MORGAN, Examiner. 2,230,164 1/1941 Myerson 328 X 2,419,084 4/1947 Myerson et a1 328

Claims (1)

1. AN ARTIFICAL TOOTH FORMED FROM TWO PARTS COMPRISING A RELATIVELY OPAQUE INNER BODY PART AND AN OUTER TRANSLUCENT ENAMEL-SIMULATING PART HAVING COMPLEMENTARY INTERFACE SURFACES AND CONNECTING TOGETHER, SAID TOOTH HAVING RESTRICTED AREA ADJACENT THE INCISAL EDGE OR OCCLUSAL SURFACE WHICH IS VISIBLE THROUGH SAID OUTER TRANSLUCENT PART ON THE LABIAL SURFACE OF THE TOOTH, SAID RESTRICTED AREA COMPRISING A SUBSTANTIALLY CONTINUOUS BAND OF PEARLESCENT MATERIAL INTERPOSED BETWEEN THE INTERFACE SURFACES OF SAID CONNECTED PARTS AND EXTENDING TRANSVERSELY ACROSS THE BODY PART OF SAID TOOTH FOR SUBSTANTIALLY

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