Patent Application
20080064011
A multi-colored shaped body according to the invention having layers arranged on top of one another can comprise:
wherein a change in color between these intermediate layers takes place in a direction which is contrary to the direction of the change in color between the main layers.
The change in colors can essentially be a change in their respective brightness. In one embodiment the change of brightness in the intermediate layers takes place in a direction which is contrary to the direction of the change in brightness between the main layers.
It has surprisingly been shown that shaped bodies formed and structured according to the invention have color boundaries between differently colored main layers that are practically imperceptible to the naked eye.
It has also been recognized that the clear perceptibility of the color boundaries between individual layers in previously known shaped bodies is enhanced by an optical illusion.
When observing neighboring surfaces differing in color or brightness, so-called lateral inhibition of neighboring receptors in the retina occurs in the human eye. Therefore, in the boundary area of two differently colored surfaces the dark surface appears darker than in areas more distant from the boundary area, but the bright area appears brighter than in areas further away from the boundary area. The higher-contrast changes perceived by the human eye are called Mach bands. By this effect the contrast at the color boundary is increased and the perception of the color boundary enhanced. Because of this effect, in a series of differently colored layers each of which is one-colored in itself, within the individual layers a color gradient is perceived which is contrary to the gradient of the colors of the individual layers. These effects are more strongly perceived with brighter colors than with darker colors.
The described optical effects are contrary to the desired aim of dental restorations to achieve a natural color gradient. Thus, the color gradient of known multi-colored shaped bodies has boundaries between the layers that are clearly perceptible. The shaped bodies according to the invention compensate or even over-compensate for these effects by the insertion of specially developed intermediate layers. A color gradient is achieved thereby in which the boundaries of the differently colored layers are no longer perceptible to the naked eye.
The subject of one embodiment of the invention is a multi-colored shaped body wherein the intermediate layers lying between two successive and differently colored main layers alternately have the colors of these main layers. A desired color gradient in which the color boundaries are practically imperceptible can thereby be achieved using relatively few colors.
Another embodiment comprises a multi-colored shaped body wherein, between two successive and differently colored main layers, precisely two intermediate layers are arranged and each of these intermediate layers has the color of the main layer which is adjacent to the respective other intermediate layer.
Accordingly, such a shaped body is also preferred which has at least one element of four layers arranged on top of one another, wherein
With shaped bodies according to the invention the total number of main and intermediate layers is at least four, i.e., there are at least two main layers and at least two intermediate layers. The shaped bodies according to the invention may have 4 to 20, in particular 4 to 10 and more particularly 4 to 8 main and intermediate layers.
The increase in contrast which occurs at the boundaries of the main layers in the absence of intermediate layers is pronounced to a greater or lesser degree, depending on the translucency and brightness of the layers involved. With shaped bodies with more than two main layers, it is therefore not absolutely necessary to insert intermediate layers at every boundary between two main layers. Thus a dental restoration which satisfies high aesthetic requirements can be manufactured from a shaped body which can be produced economically.
In an alternative embodiment a shaped body according to the invention has eight layers arranged on top of one another, wherein
A shaped body according to the invention may have a height of 10 mm to 20 mm, more particularly 14 mm to 16 mm.
The main layers of the shaped body according to the invention may have a thickness of more than 0.5 mm, in particular more than 0.5 mm and up to 15 mm, more than 0.5 mm and up to 10 mm, and still more particularly 0.7 mm to 8 mm.
The intermediate layers of the shaped body according to the invention may have a thickness of up to 0.5 mm, in particular 0.01 mm to 0.5 mm, more particularly 0.1 mm to 0.5 mm, and still more particularly 0.2 mm to 0.4 mm.
A shaped body according to the invention can be formed of any material suitable for producing shaped bodies for dental restorations. Such materials include ceramics, glass ceramics, plastics, inorganic-organic composites or mixtures thereof.
A shaped body, according to one embodiment, contains (a) SiO2, (b) Al2O3 and (c) K2O and/or Na2O. A shaped body according to another embodiment is made from Al2O3 and/or ZrO2 ceramic material.
Differently colored layers can be of the same material which is differently colored in each case, or can be formed of different materials.
The layering of the shaped bodies is can be based on the layering of the color codes common in the dental industry, such as the Vitapan classical® or the Vita 3D Master®, both from VITA Zahnfabrik H. Rauter GmbH & Co. KG, or Ivoclar Vivadent AG's Chromascop®. The tooth models of these color codes in each case define only one color, but similar to teeth are built up of layers of different material mixtures and/or colors and/or translucencies, and are based on the different colors of human teeth. This basic color allocation is preferably also used in the shaped bodies according to the invention, with the result that the dental restorations produced from them correspond very closely to the natural tooth.
According to a further embodiment of the invention a multi-colored shaped body for producing dental restorations may comprise
The main layers of this other shaped body according to the invention preferably have a thickness of more than 0.5 mm, in particular more than 0.5 mm and up to 15 mm, more than 0.5 mm and up to 10 mm, and still more particularly 0.7 mm to 8 mm.
The intermediate layer of this other shaped body according to the invention may have a thickness of up to 0.5 mm, in particular 0.01 mm to 0.5 mm, particularly 0.1 mm to 0.5 mm, and more particularly 0.2 mm to 0.4 mm.
Further embodiments of the invention have the properties with respect to preferred numbers of layers, preferred heights of the shaped body and preferred materials as described above for the other embodiments.
The invention also relates to a process for manufacturing the multi-colored shaped bodies according to the invention having layers arranged on top of one an other, in which the main layers and intermediate layers are arranged on top of one another such that a shaped body according to the invention is obtained.
Finally the invention also relates to the use of the multi-colored shaped bodies according to the invention for the manufacture of dental restorations. The manufacture of dental restorations can be computer-aided, in particular by means of CAD/CAM methods. Preferred dental restorations are artificial teeth, inlays, onlays, bridges and crowns.
The invention is explained in more detail below with reference to the following illustrative, non-limiting examples.
For the manufacture of a multi-colored shaped body having differently colored layers, the following materials (glass ceramic powders) are used:
By appropriate pigment addition, the colorings M1 and M2 of the glass ceramic material are produced, wherein M1, for example, corresponds to the dentine color A2 according to Vitapan classical® and has a high opacity. M2 corresponds to an incisor color and has a lower opacity. By different mixing of the materials M1 and M2 four differently colored material compositions A to D result, which are composed as follows:
The individual materials are introduced gradually in a customary form of a compression mold so that the following series of layers results:
After filling the compression mold with the individual layers the green body is produced in known manner by dry pressing, and then a processable shaped body with an overall height of approximately 10 to 15 mm is produced by debindering and sintering. This shaped body may optionally be subjected to further processing.
In the resulting shaped body the intermediate layers have a layer thickness of about 0.2 to about 0.4 mm. With this shaped body, and in a dental restoration produced from it, the changes between the individual layers are surprisingly imperceptible to the naked eye.
For the manufacture of a multi-colored shaped body having fundamentally differently colored layers, the following materials (glass ceramic powders) are used:
By appropriate pigment addition, the colorings M1 and M2 of the glass ceramic material are produced, wherein M1, for example, corresponds to the dentine color A2 according to Vitapan classical® and has a high opacity. M2 corresponds to an incisor color and has a lower opacity. By different mixing of the materials M1 and M2 four differently colored material compositions A to D result, and from these in turn six differently colored materials of the intermediate layers AB1, AB2, BC1, BC2, CD1, CD2:
The individual materials are introduced gradually in a customary form of a compression mold so that the following series of layers results:
After filling the compression mold with the individual layers the green body is produced in known manner by dry pressing, and then processable shaped body with an overall height of approximately 10 to 15 mm is produced by debindering and sintering. This shaped body may optionally be subjected to further processing.
In the thus-obtained shaped body the intermediate layers have a layer thickness of approximately 0.2 to approximately 0.4 mm. With this shaped body and with a dental restoration produced from it, the changes between the individual layers are surprisingly imperceptible to the naked eye.
For the manufacture of a multi-colored shaped body having differently colored layers, the following materials (glass ceramic powders) are used:
By appropriate pigment addition, the colorings M1 and M2 of the glass ceramic material are produced, wherein M1 for example corresponds to the dentine color A2 according to Vitapan classical® and has a high opacity. M2 corresponds to an incisor color and has a lower opacity. By different mixing of the materials M1 and M2 four differently colored material compositions A to D result, and from these in turn three differently colored materials of the intermediate layers AB, BC, CD:
The individual materials are introduced gradually in a customary form of a compression mold so that the following series of layers results:
After filling the compression mold with the individual layers the green body is produced in known manner by dry pressing, and then a processable shaped body with an overall height of approximately 10 to 15 mm is produced by debindering and sintering. This shaped body may optionally be subjected to further processing.
In the thus-obtained shaped body the intermediate layers have a layer thickness of approximately 0.2 to approximately 0.4 mm. With this shaped body and with a dental restoration produced from it, the changes between the individual layers are surprisingly imperceptible to the naked eye.
All numbers expressing quantities or parameters used in the specification are to be understood as additionally being modified in all instances by the term “about”. Notwithstanding that the numerical ranges and parameters set forth, the broad scope of the subject matter presented herein are approximations, the numerical values set forth are indicated as precisely as possible. For example, any numerical value may inherently contains certain errors, evidenced by the standard deviation associated with their respective measurement techniques, or round-off errors and inaccuracies.
Although the present invention has been described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without department from the spirit and scope of the invention as defined in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 06120608.2 | Sep 2006 | EP | regional |
