Patent Grant
9308063
This application claims foreign priority benefits under 35 U.S.C. §119(a)-(d) from German patent application ser. no. P 10 2007 050 439.1 filed Oct. 22, 2007.
The invention relates to anterior teeth such as an incisor tooth or canine tooth which is built up in layers, and more particularly to such a tooth wherein a cutting-edge material at least partially covers a dentine material, and to a method of making such a tooth.
It has long been known for artificial teeth, in particular incisor teeth or canine teeth, to be built up from layers. In doing so, a cutting-edge material is built up such that it covers most of a dentine material, apart from the basal area of the dentine material. The dentine material can be joined to the cutting-edge material in any suitable way desired.
Thus, it is known from DE-A1 38 27 657, for example, to first build up a basic body of dentine material and then to injection-mold around the latter.
It is known, not only in plastic teeth, but also in ceramic teeth, to vary the layer thickness of the cutting-edge material in order to give an appearance resembling natural teeth. An example of this is the solution according to German specification 1 903 935.
The cutting-edge material is typically translucent, and the dentine material is somewhat opaque. It has also already been proposed, however, to increase the translucency of the dentine material. In this case, especially if a metal skeleton is used, a special opaquer is employed to veneer the metal skeleton. To provide the translucency, the cutting-edge material is often made quite thick. Although this gives the tooth the desired impression of translucency, it also gives the tooth a slightly “washed-out” look.
An improvement to these known solutions is known from DE 101 27 728. In the solution according to DE 101 27 728, the cutting-edge material is comparatively thin and has an uneven layer thickness. The uneven layer thickness is intended to improve the similarity to the natural tooth. However, this means that the tooth has a rather uneven effect specifically in the incisal area. The layer thickness should also not be chosen too small, in order to ensure that sprues that are used to produce the dentine material cannot be seen through the cutting-edge material. Such sprues are not very satisfactory from the technical point of view and also unsatisfactory from the esthetic point of view.
To improve the “technical” look of artificial teeth, attempts have therefore been made, in the recent years and decades, to improve the similarity to the natural appearance by using specific colorations. Mention may be made here of the known painting technique, which is still used regularly even today, even though it is very much dependent on the skill of the dental technician and is labor-intensive.
Moreover, it has also already been proposed to incorporate a color gradient within the layers. This solution, however, is extremely difficult to implement on account of the technical difficulties involved, especially since it is necessary to establish an exact reference point, which is a spatial one and is therefore difficult to define.
To remove plastic bodies from molds, it has become known to select the mold separation lines such that the fewest possible undercuts are present. Typically, the removal of mold halves with undercuts typically requires the provision of complicated slides, which also impair the precision. Also in light of these considerations, typical teeth, particularly plastic teeth, are generally produced free of undercuts and tapering obliquely toward the incisal side, the mold separation taking place at the “thickest” point of the tooth which, in the case of incisor teeth, may be arranged relatively near to the incisal area. This too has led to rather smooth and straight surfaces.
Against the background of these disadvantages, the object of the invention is to create an anterior tooth which is built up in layers, the dentine material at its occlusal end having projections and/or irregularities which extend in the occlusal direction, and which, while being easy to produce and aesthetically much improved, still gives an appearance approximating the natural teeth.
According to the invention, it is particularly expedient that the incisor tooth or canine tooth built up in layers according to the invention is not subject to fixed specifications in terms of its outer shape. Thus, it is possible, in an incisor tooth, to provide a substantially straight or at most slightly undulated incisal cutting edge of the cutting-edge material. This represents a considerable advance compared to a markedly undulated design, as has already been sought to achieve a natural appearance.
Thus, according to the invention, the undulation or irregularity of the outer cutting edge can be less than 30%, in particular less than 20% and preferably approximately 10% of the layer thickness of the cutting-edge material at this point.
However, this does not prevent the design according to the invention with projections and/or irregularities extending in the occlusal direction. According to the invention, the projections and/or irregularities of the dentine material, that is to say of the boundary layer between the dentine material and cutting-edge material, over a certain predetermined height, which is different than 0 and much less than half of the total length of a tooth. The height of the irregularities or projections can, for example, be only 1/20 of the height of the tooth. This is expedient, for example, if a very small layer thickness is realized for the cutting-edge material, which can again amount for example to 1/10 or even also 1/20 of the height of a tooth. However, the height of the irregularities can also be chosen substantially greater, which is expedient if the layer thickness of the cutting-edge material is chosen substantially greater, for example 20% or even 30% of the tooth height, in order to improve the translucency.
According to the invention, the thickness of the cutting-edge material and the height of the projections and/or irregularities are to this extent correlated with one another, it being particularly expedient if the thickness of the cutting-edge material, with a small projection height, is slightly greater, and, with a large projection height, slightly smaller than the projection height.
According to the invention, it is surprisingly possible, by simple means, to hugely improve the optical properties of the incisor teeth or canine teeth, specifically such that a washed-out impression and also too “technical” an impression are avoided.
According to the invention, it is particularly expedient that the invention makes it possible to work with a comparatively large layer thickness for the cutting-edge materials, with an aesthetically very pleasing effect. The layer thickness can, for example, expediently be at least 20% of the length of a tooth. This permits a mechanically improved design, since too thin layer thicknesses are technically more difficult to handle, especially if the adherence between cutting-edge material and dentine material cannot easily be overcome, because of the different chemical substances from which they are built up, for example if different ceramic types (zirconium oxide or silicate ceramics) are used. It has also been found that the greater layer thickness improves the stability with respect to different coefficients of thermal expansion, which are in most cases very problematic in different ceramics.
The tendency of the cutting-edge material to chip off is surprisingly much lower, and, according to the invention, the realization of irregularities also having a supporting effect here, since in this way the adherence also appears to be improved.
The realization of irregularities at the boundary layer between cutting-edge material and dentine material has a dual function. The fact that an advance can be achieved to this extent is surprising since the roughness of ceramic surfaces is known per se, and it is particularly expedient according to the invention if neither the cutting-edge material at its interface to the dentine material nor the dentine material at its interface to the cutting-edge material is subjected to machining operations. Rather, it is preferable in this connection to use a specially designed core mold for shaping the boundary layer, the core mold having, at its incisal or occlusal end, the surface structure and projections and irregularities that the interface between dentine material and cutting-edge material is later intended to have.
This production is preferred if first the cutting-edge material and then the dentine material is cast for realizing the tooth according to the invention.
Alternatively, layering from the inside outward is also possible. In this method, a core mold is first cast for the dentine material, its inner profile again corresponding exactly to the interface between cutting-edge material and dentine material. Thereafter, the cast dentine material itself is used as inner mold for the cutting-edge material, and the cutting-edge material is introduced into the resulting layered mold cavity, the irregularities once again achieving a particularly good anchoring especially also in the strongly loaded incisal area of the tooth.
The solution according to the invention is particularly well suited for realization of ceramic teeth. While plastic material, because of the used material, is easier to produce, since plastic is relatively elastic compared to ceramic and therefore better tolerates inner stresses, it is possible according to the invention, by surprisingly simple means, to solve the problem of realizing a ceramic with natural appearance without generating technical problems.
According to the invention, it is also particularly expedient to combine a relatively hard dentine material with a by contrast softer cutting-edge material. Different materials can also be realized because of the good anchoring, and the use of a softer cutting-edge material has the advantage that the antagonist of the restored tooth is less strongly affected.
Further advantages, details and features will become clear from the following description of two illustrative embodiments, with reference being made to the drawings, in which:
For simplicity, the incisor tooth 14, which is to be regarded as tooth II, will be considered here. The tooth 14 is basically built up of dentine material 28 which, in the illustrative embodiment shown, is completely surrounded by cutting-edge material 30. Although the cutting-edge material in the illustrative embodiments shown here extends also over the basal end 26, it will be appreciated that it is also possible to provide the dentine material there.
In the illustrative embodiment shown, the cutting-edge material accordingly extends in the manner of a three-dimensional cover layer around the dentine material 28. The dentine material 28 extends over its buccal end area 32 and its distal and mesial side faces 34 and 36, respectively, in each case substantially straight, apart from a slight bulge or, if appropriate, a slight undulation.
By contrast, according to the invention, the occlusal or incisal end area 38 of the dentine material is strongly undulated. The undulation or the provision of irregularities there corresponds to a height which, in the example shown, corresponds at most to 6% of the height of the tooth.
The dentine material 28 is also completely covered by the cutting-edge material 30 there. The layer thickness there, that is to say in the occlusal area, corresponds on average to once again approximately 6% of the height of the cutting-edge material. It is preferable that the undulation or the formation of irregularities is quite intensive, but in each case provided with radii. Thus, the maximum inclination angle 40 of oblique surfaces in the area of the occlusal interface between cutting-edge material and dentine material is approximately 60% in the incisor tooth 14. Mainly, however, the inclination angle 40 is much smaller, and typically lies at 10% to 20%.
The minimum layer thickness of the cutting-edge material 30 in the incisal end area 38 is 4% of the tooth height.
The values specified above can be varied between individual incisor or canine teeth and also between individual sets of teeth, in order to obtain an impression that is life-like and very similar to the natural appearance of the teeth.
Thus, the minimum layer thickness in the incisal area of the cutting-edge material 30 is 8% for the canine tooth 12. At one location there, a distinct projection 42 is provided, whereas otherwise there is only a slightly undulated configuration of the boundary layer 44 between cutting-edge material and dentine material in the incisal area.
By contrast, the minimum layer thickness of the cutting-edge material 30 in the incisal area 46 of the tooth 18 is only 1% of the tooth height; a quite intensively formed fissure 48 is provided, which laterally divides off a projection 42 in the mesial or distal direction.
Similar configurations are provided for the teeth 16, 20 and 22, the views shown in the figures pointing to examples of possible deviations.
In a manner known per se, the opacity of the dentine material 28 is greater than the opacity of the cutting-edge material 30. The irregularities 42, 46 and 48 alternate, and smaller and greater radii are likewise provided. The irregularities are asymmetrical fissures, incisions, or trenches formed in the dentine material (28) and filled by cutting-edge material (30). Moreover, the irregularities do not extend only in the direction of the drawing, but also in the direction perpendicular to the drawing. It is also possible for the strong irregularities in the boundary layer 44 to be followed by an irregularity reduced to ⅓ or even to 1/10 in the area of the incisal cutting edge. In this way, it is still possible to obtain a substantially straight cutting edge, which nevertheless resembles a natural tooth shape.
While a preferred form of this invention has been described above and shown in the accompanying drawings, it should be understood that applicant does not intend to be limited to the particular details described above and illustrated in the accompanying drawings, but intends to be limited only to the scope of the invention as defined by the following claims. In this regard, the term “means for” as used in the claims is intended to include not only the designs illustrated in the drawings of this application and the equivalent designs discussed in the text, but it is also intended to cover other equivalents now known to those skilled in the art, or those equivalents which may become known to those skilled in the art in the future.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 050 439 | Oct 2007 | DE | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 2300305 | Myerson | Oct 1942 | A |
| 3218711 | Connan | Nov 1965 | A |
| 3395454 | Frush | Aug 1968 | A |
| 3449832 | Connan | Jun 1969 | A |
| 5308243 | Emmons | May 1994 | A |
| 5624262 | Yarovesky et al. | Apr 1997 | A |
| 5718585 | Dehoff et al. | Feb 1998 | A |
| 5800164 | Pfau | Sep 1998 | A |
| 5989031 | Kura et al. | Nov 1999 | A |
| 6488503 | Lichkus | Dec 2002 | B1 |
| 6755646 | Zun | Jun 2004 | B2 |
| 6923649 | Oswald et al. | Aug 2005 | B2 |
| 6951459 | Weinstein | Oct 2005 | B2 |
| 7086863 | Van der Zel | Aug 2006 | B2 |
| 20020175430 | Glidewell | Nov 2002 | A1 |
| 20080220395 | Marshall et al. | Sep 2008 | A1 |
| Number | Date | Country |
|---|---|---|
| 248607 | Aug 1966 | AT |
| 3827657 | Feb 1990 | DE |
| 101 27 728 | Dec 2002 | DE |
| 10127728 | Dec 2002 | DE |
| 696 25 012 | Oct 2003 | DE |
| 1 121 908 | Aug 2001 | EP |
| 2 883 466 | Sep 2006 | FR |
| 1013548 | Dec 1965 | GB |
| Number | Date | Country | |
|---|---|---|---|
| 20090104584 A1 | Apr 2009 | US |
