Multi component milling blank

Abstract

The present invention relates to a milling blank for generating a splint, comprising at least two phases, particularly a flexible phase FP and a stiff phase SP, characterised in that the stiff phase SP has a higher Shore hardness at body temperature than the flexible phase FP at body temperature, namely at least 15 Shore D higher.

Description

[0001] Multi component milling blank

[0002] Field

[0003] The present invention relates to a milling blank for generating a blank, typically used in the field of dental medicine.

[0004] Background

[0005] A variety of materials are used today for the manufacture of dental splints, such as occlusal or protrusion splints, which differ in terms of efficiency, wearing comfort and clinical indication. Depending on the application, however, it can generally be assumed that the more flexible a splint is, the more comfortable it is to wear and the less effective it is. For example, splint materials based on PMMA are used for adjusted bite splints. Dental splints of this material class comprise low deformations under pressure load (e.g. grinding) and slide more easily against each other during opposing movements of the lower and upper jaw compared to more flexible splint materials. However, hard splints create disturbing sensations in the patient, which affects his speech, swallowing and chewing sensations. To avoid these disturbances, more flexible materials based on e.g. polycarbonate or polyethylene terephthalate glycol are used nowadays. This is due to the fact that by means of such splint materials on the one hand a better adaptation of the splint to the tooth and the soft tissue is realized and on the other hand the pressure on the tooth surfaces is reduced. A disadvantage of dental splints made of these materials is that permanent deformation can occur due to mechanical influences. This can happen, for example, when a very tightly fitting splint is removed from the mouth. T o avoid this, the skilled person is nowadays also familiar with splint materials with a so-called thermomemory effect (insert own patent here), which are hard-flexible when inserted into the mouth, i.e. at room temperature, and whose flexibility and resilience are increased by body heat. This effect also has a very advantageous effect on the wearing comfort of mucosa- supported splints compared to all the above-mentioned material classes.

[0006] Generally, however, as a result of the increase in flexibility of such splints, the frictional forces between the occlusal surfaces increase, as described above, and thus significantly reduce the wearing comfort.

[0007] It is therefore the objective of the present invention to provide a means for generating a dental splint from a blank which has a higher hardness at the occlusal surfaces (or also incisal edges) than at the other contact surfaces to the teeth and soft tissue.

[0008] This objective is solved by the subject matter of independent claim 1. Advantageous embodiments of the invention are stated in subclaims 2 - 17. In this case, the blank is composed of at least 2 components which differ in terms of their Shore hardnesses by at least 7 Shore D at room temperature and at least 15 Shore D at body temperature. According to the invention, it is advantageous that there is no further layer, such as an adhesive layer, between the two material layers, i.e. incisal / occlusal material and tooth / soft tissue material. In the spirit of the invention, such a layer is avoided. Both materials are polymerized to each other under the action of pressure and heat to create a direct chemical bonding of the two materials. This allows force peaks to be dissipated more easily, thus increasing durability and strength.

[0009] Summary of the Invention

[0010] A first aspect of the present invention relates to a milling blank for generating a splint, wherein the milling blank comprises at least two phases, particularly a flexible phase FP and a stiff phase SP, characterised in that the stiff phase SP has a higher Shore hardness at body temperature than the flexible phase FP at body temperature, namely at least 15 Shore D higher. In particular, the milling blank for generating a splint can be used to generate a dental splint.

[0011] Terms and definitions

[0012] For purposes of interpreting this specification, the following definitions will apply and whenever appropriate, terms used in the singular will also include the plural and vice versa. In the event that any definition set forth below conflicts with any document incorporated herein by reference, the definition set forth shall control.

[0013] The terms “comprising”, “having”, “containing”, and “including”, and other similar forms, and grammatical equivalents thereof, as used herein, are intended to be equivalent in meaning and to be open-ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. For example, an article “comprising” components A, B, and C can consist of (i.e., contain only) components A, B, and C, or can contain not only components A, B, and C but also one or more other components. As such, it is intended and understood that “comprises” and similar forms thereof, and grammatical equivalents thereof, include disclosure of embodiments of “consisting essentially of” or “consisting of.”

[0014] Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure. Reference to “about” a value or parameter herein includes (and describes) variations that are directed to that value or parameter per se. For example, description referring to “about X” includes description of “X”.

[0015] As used herein, including in the appended claims, the singular forms “a”, “or” and “the” include plural referents unless the context clearly dictates otherwise.

[0016] "And / or" where used herein is to be taken as specific recitation of each of the two specified features or components with or without the other. Thus, the term "and / or" as used in a phrase such as "A and / or B" herein is intended to include "A and B," "A or B," "A" (alone), and "B" (alone). Likewise, the term "and / or" as used in a phrase such as "A, B, and / or C" is intended to encompass each of the following aspects: A, B, and C; A, B, or C; A or C; A or B; B or C; A and C; A and B; B and C; A (alone); B (alone); and C (alone).

[0017] The formulae of the present specification follow the convention of organic chemistry to not show hydrogen atoms on carbon scaffolds. Carbon is tetravalent and bonds not shown are assumed to be hydrogen unless shown otherwise.

[0018] The term flexible phase in the context of the specification relates to a material that has a low shore hardness. The flexible phase becomes reduced its hardness and becomes more flexible at body temperature making it adjustable around the teeth, and in case of a splint is surrounding the tooth. The flexible phase may comprise an internal hardness gradient with decreasing shore hardness towards the soft tissue of the jaw.

[0019] The term stiff phase in the context of the specification relates to a material with a high shore hardness. The stiff phase in case of a splint is located at the occlusal plane. The stiff phase may comprise an internal hardness gradient with increasing shore hardness towards the occlusal plane.

[0020] The term gradient in the context of the specification relates to a gradual change in shore hardness. The gradient can be implemented through 3D printed layers, wherein each layer varies in their shore hardness. Through the 3D printed layers, the gradient increments can be influenced by the layer thickness. The thinner the layer, the higher the gradient, the thicker the layer, the smaller the gradient.

[0021] The term Shore hardness in the context of the specification relates to a measurement for the hardness of a material, particularly a polymer. The Shore hardness is measured using a Shore durometer. High Shore values indicate a greater resistance to indentation and thus harder materials. Lower numbers indicate less resistance and softer materials. The Shore A scale describes softer materials, the Shore D scale describes harder materials. The term thermo memory effect in the context of the specification relates to a material that becomes flexible at body temperature and adapts optimally to the tooth surface and in turn becomes stiff at room temperature.

[0022] Description of the Invention

[0023] A first aspect of the present invention relates to a milling blank for generating a splint, wherein the milling blank comprises at least two phases, particularly a flexible phase FP and a stiff phase SP, characterised in that the stiff phase SP has a higher Shore hardness at body temperature than the flexible phase FP at body temperature, namely at least 15 Shore D higher. In particular, the milling blank for generating a splint can be used to generate a dental splint.

[0024] The differences between the Shore Hardness is calculated between the highest part of Shore hardiness of the hard phase HP and the lowest part of the Shore hardness of the soft phase SP.

[0025] On the one hand, combination of flexible phase and stiff phase increases wearing comfort by reducing friction during jaw movements which prohibits disturbing sensations for the patient. By combining a flexible phase as well as a stiff phase, a milling blank for generating a splint is obtained which is advantageous in comparison with the state of the art.

[0026] In certain embodiments, the flexible phase FP comprises a soft polymer A and the stiff phase SP comprises a hard polymer B.

[0027] In further embodiments, the flexible phase FP consists of a soft polymer A and the stiff phase SP consists of a hard polymer B.

[0028] In certain embodiments, the stiff phase SP has a higher Shore hardness at body temperature than the flexible phase FP at body temperature, namely at least 18 Shore D higher, particularly the stiff phase SP has a higher Shore hardness at body temperature than the flexible phase FP at body temperature, namely at least 20 Shore D higher, more particularly the stiff phase SP has a higher Shore hardness at body temperature than the flexible phase FP at body temperature, namely at least 22 Shore D higher.

[0029] In further embodiments, the stiff phase SP has a higher Shore hardness at body temperature than the flexible phase FP at body temperature, namely at least 25 shore D higher. In another particular embodiment of the first aspect of the invention, the stiff phase SP has a higher Shore hardness at body temperature than the flexible phase FP at body temperature, namely at least 30 shore D higher. In another embodiment of the first aspect of the invention, the stiff phase SP has a higher Shore hardness at body temperature than the flexible phase FP at body temperature, namely at least 15 to 30 shore D higher. In certain embodiments, the flexible phase FP comprises a thermomemory effect, a temperature-dependent memory effect so that the material returns to its original shape after deformation during heating. The material becomes flexible at body temperature and adapts optimally to the tooth surface. This increases the wearing comfort of the splint and minimizes the risk of breakage.

[0030] In further certain embodiments, the soft polymer A of the flexile phase FP and the hard polymer B of the stiff phase SP is a polymer P selected from the group consisting of polyalkyl methacrylate, polycycloalkyl methacrylate, polycycloalkyl acrylate and polyalkyl acrylate or a polymerized component of a thermoplastic comprising a polymer P selected from the group consisting of polyalkyl methacrylate, polycycloalkyl methacrylate, polycycloalkyl acrylate and polyalkyl acrylate or at least one copolymer CP produced of at least one monomers M, particularly two monomers M, particularly selected from the group consisting of an alkyl methacrylate, an alkyl acrylate, a cycloalkyl methacrylate and a cycloalkyl acrylate, wherein the cycloalkyl methacrylate and the cycloalkyl acrylate are unsubstituted or substituted with at least one -Ci-4-alkyl, -OH or Ci-4-alcohol.

[0031] In certain embodiments, the polymer P of the soft polymer A and / or the polymer P of the hard polymer B is selected from the group consisting of poly-Ci- -alkyl methacrylate, poly-Ci-10- alkyl acrylate, poly-Cs-is-cycloalkyl methacrylate und poly-Cs-is-cycloalkyl acrylate.

[0032] In certain embodiments, the polymer P of the soft polymer A polyethyl methacrylate (PEMA) and / or a polyethyl methacrylate-polymethyl methacrylate copolymer (PEMA-PMMA).

[0033] In certain embodiments, the polymer P of the hard polymer B is polymethyl methacrylate (PMMA) and / or a polyethyl methacrylate-polymethyl methacrylate copolymer (PEMA-PMMA).

[0034] In other certain embodiments, the copolymer CP is derived from monomers M selected from the group consisting of methyl methacrylate, ethyl methacrylate, ethyl acrylate, ethoxyethyl acrylate, tetrahydrofurfuryl methacrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, isobornyl methacrylate, Ethylene dimethacrylate and ethoxyethyl methacrylate, particularly from the group consisting of 2-ethoxymethacrylate, 2-ethoxy acrylate, tetrahydrofurfuryl acrylate and tetrahydrofurfuryl methacrylate.

[0035] In certain embodiments, the polymer P of the soft polymer A polyethyl methacrylate (PEMA) and / or a polyethyl methacrylate-polymethyl methacrylate copolymer (PEMA-PMMA) and the copolymer CP is derived from monomers M selected from the group consisting of methyl methacrylate, ethyl methacrylate, ethyl acrylate, ethoxyethyl acrylate, tetrahydrofurfuryl methacrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, isobornyl methacrylate and ethoxyethyl methacrylate, particularly from the group consisting of 2-ethoxymethacrylate, 2- ethoxy acrylate, tetrahydrofurfuryl acrylate and tetrahydrofurfuryl methacrylate.

[0036] In certain embodiments, the polymer P of the hard polymer B is polymethyl methacrylate (PMMA) and / or a polyethyl methacrylate-polymethyl methacrylate copolymer (PEMA-PMMA) and the copolymer CP is derived from monomers M selected from the group consisting of methyl methacrylate, ethyl methacrylate, ethyl acrylate, ethoxyethyl acrylate, tetrahydrofurfuryl methacrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, isobornyl methacrylate and ethoxyethyl methacrylate, particularly from the group consisting of 2-ethoxymethacrylate, 2- ethoxy acrylate, tetrahydrofurfuryl acrylate and tetrahydrofurfuryl methacrylate.

[0037] In certain embodiments, the soft polymer A of the flexible phase FP is a polymer, such as Thermeo®, derived from a first component FCA comprising a polyethyl methacrylate polymer (PEMA) or a polyethyl methacrylate-polymethyl methacrylate copolymer (PEMA-PMMA), and a second component SCB comprises at least one alkyl acrylate and / or one alkyl methacrylate monomer in which the polyethyl methacrylate polymer (PEMA) or the polyethyl methacrylate- polymethyl methacrylate copolymer (PEMA-PMMA) of component FCA is at least partially soluble, wherein the alkyl acrylate and / or alkyl methacrylate monomer of component SCB is at least one monomer of the group methyl methacrylate, ethyl methacrylate, ethyl acrylate, ethoxyethyl acrylate, tetrahydrofurfuryl methacrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, isobornyl methacrylate and ethoxyethyl methacrylate.

[0038] The mass ratio of components FCA and SCB is 0.5 - 2.

[0039] In certain embodiments, the hard polymer B of the stiff phase SP is a polymer, derived from a first component FCA comprising a polymethyl methacrylate (PMMA) or polyethyl methacrylate-polymethyl methacrylate copolymer (PEMA-PMMA), and a second component SCB comprises at least one alkyl acrylate and / or one alkyl methacrylate monomer, in which the polyethyl methacrylate polymer (PMMA) or the polyethyl methacrylate-polymethyl methacrylate copolymer (PEMA-PMMA) of component FCA is at least partially soluble, wherein the alkyl acrylate and / or alkyl methacrylate monomer of component SCB is at least one monomer of the group methyl methacrylate, ethyl methacrylate, Ethylene dimethacrylate, tetraethylene glycol dimethacrylate, ethyl acrylate, ethoxyethyl acrylate, tetrahydrofurfuryl methacrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, isobornyl methacrylate and ethoxyethyl methacrylateis, particularly methyl methacrylate and tetraethylene glycol di methacrylate.

[0040] In certain embodiments of the first aspect of the invention, the soft polymer A comprises as a polymer P at least 10 % polyethyl methacryate (PEMA), particularly 20 % polyethyl methacrylate (PEMA), more particularly the soft component A comprises at least 30 % polyethyl methacrylate (PEMA), wherein the soft component A may further comprise polymethyl methacrylate (PMMA).

[0041] In certain embodiments, the hard component B comprises at least 60 % polymethyl methacrylate (PMMA), particularly the hard component B comprises at least 80 % polymethyl methacrylate (PMMA).. In more specific embodiments, the hard component B may further comprise polyethyl methacrylate (PEMA).

[0042] In certain embodiments, the flexible phase FP and / or stiff phase SP further comprises an initiator, a plasticiser and an activator.

[0043] In further embodiments, the milling blank comprises layers which generate a hardness gradient in Z-direction through the flexible phase FP and the stiff phase SP. Alternatively, in certain embodiments, the milling blank comprises a hardness gradient in Z-direction through the flexible phase FP and the stiff phase SP.

[0044] In certain embodiments, the Shore hardness of the flexible phase FP is between 20 Shore A and 45 Shore D at body temperature. In other embodiments, the Shore hardness of the flexible phase FP is between 20 Shore A and 40 Shore D at body temperature. In other embodiments, the Shore hardness of the flexible phase FP is between 20 Shore A and 35 Shore D at body temperature. In other embodiments, the Shore hardness of the flexible phase FP is between 20 Shore A and 30 Shore D at body temperature. In other embodiments, the Shore hardness of the flexible phase FP is between 20 Shore A and 25 Shore D at body temperature.

[0045] In further embodiments of the first aspect of the invention, the Shore hardness of the stiff phase SP is at least 60 Shore D at body temperature, particularly wherein the Shore hardness of the stiff phase SP is 60 to 95 Shore D, more particularly the Shore hardness of the stiff phase SP is 60 to 90 Shore D. In certain embodiments, the Shore hardness of the stiff phase SP is between 60 to 85 Shore D at body temperature. In further embodiments, the Shore hardness of the stiff phase SP is between 60 to 80 Shore D at body temperature.

[0046] In further embodiments, the hardness gradient between the softest point of the flexible phase FP and the stiffest point of the stiff phase SP is at least 15 Shore D.

[0047] In further embodiments, the flexible phase FP and the stiff phase SP are directly connected to each other, particularly polymerised together, more particularly polymerised through pressure and heat. In further embodiments, the flexible phase FP and the stiff phase SP are directly connected to each other, particularly polymerised together, more particularly polymerised through pressure and heat in an alternating fashion.

[0048] In certain embodiments, the flexible phase FP and the stiff phase SP form an equal wave like structure or a planar structure. In certain embodiments, the flexible phase FP is planar and the stiff phase SP forms a wave like structure.

[0049] In certain embodiments, the flexible phase FP and the stiff phase SP form an equal wave like structure . In certain embodiments, each of the two phases of flexible phase FP and stiff phase SP can be arranged such that a desired milling blank can be generated. For example, the stiff phase SP spans the entire base of the milling blank, wherein the flexible phase FP is arranged such on top of the stiff phase SP that it only covers those parts necessary for generating a milling blank. This can for example be advantageous in order to save material and subsequently reduce waste.

[0050] The invention is further illustrated by the following examples and figures, from which further embodiments and advantages can be drawn. These examples are meant to illustrate the invention but not to limit its scope. It is shown in figure

[0051] Fig. 1 : a flexible phase A and a stiff phase B (striped) of a milling blank with flat interface in view from the side,

[0052] Fig. 2: cut-view through a 2-component milling blank with a milled dental splint with a flexible phase A and a stiff phase B (striped),

[0053] Fig. 3: structured part (flexible phase A) of a 2-component round milling blank,

[0054] Fig. 4: 2-component milling blank consisting of a flexible phase A and stiff phase B

[0055] (striped),

[0056] Fig. 5: sectional view of a structured 2-component milling blank, and

[0057] Fig. 6: cross-sectional view through a structured 2-component round plate.

[0058] Examples

[0059] Flexible Phase 1:

[0060] A material made from two components FCA and SCB is used for generating the flexible phase, wherein exemplary compositions of which are shown in the table below.

[0061] Table 1 : Component A

[0062] Component FCA Mass fraction, %

[0063] Polyethyl methacrylate 99

[0064] 1-Benzyl-5-phenylbarbituric acid 1 Table 2:

[0065] Component SCB Mass fraction, %

[0066] Ethoxyethyl methacrylate 49,73

[0067] Tetrahydrofurfuryl methacrylate 33,2

[0068] 1 ,2 Cyclohexanedicarboxylic acid diisononyl ester 16,5

[0069] Dilauryldimethylammonium chloride 0,4

[0070] 1% copper(ll) acetylacetonate solution in MMA 0,17

[0071] The two components according to the invention are for example mixed in the ratio A : B = 100 : 75 with a spatula in a beaker and then cured in a pressure pot (Polymax, Fa. Dreve) at 50°C and 6 bar for 45 min without bubbles in a duplicating silicone mold. A milling blank with a diameter of 98 mm and a thickness of 18 mm is obtained.

[0072] Test specimens with dimensions 5x5x80 mm are then generated from this milling blank using a milling machine (Otofab 1 , pro3dure). Alternatively, the production of medical molded parts takes place on the basis of 3-dimensional data. The test specimens are then tempered at 23 °C and 37 °C for 24 h and then bent through 90° in the center. The relaxation of the angle is subsequently recorded time-dependently at the two above-mentioned temperatures in order to document the temperature-dependent memory effect. It is shown that the formulation according to the invention comprises a temperaturedependent memory effect by means of which molded bodies, which are deformed at room temperature, almost return to their original shape due to body heat.

[0073] Stiff Phase 2:

[0074] A material made from two components FCA and SCB is used for generating the stiff phase, wherein exemplary compositions of which are shown in below.

[0075] Table 3: Component SCB

[0076] Component SCB Mass fraction, %

[0077] Methacrylic acid methyl ester up to 90 Di(meth)acrylate (e.g. tetraethylene glycol up to 10 dimethacrylate

[0078] Crosslinker (> 3 functional acrylate and or up to 10 methacrylate groups)

[0079] Dilauryldimethylammonium chloride up to 0.4

[0080] Table 4: Component FCA

[0081] Component FCA Mass fraction, %

[0082] Polymethylmethacrylat up to 99

[0083] Polyethylmethacrylat up to 20

[0084] 1-Benzyl-5-phenylbarbitursaure or comparables up to 1 thereof

[0085] Both Phases are polymerized to each other under the action of pressure and heat to create a direct chemical bonding of the two materials. io

Claims

Claims:

1. A milling blank for generating a splint, comprising at least two phases, particularly a flexible phase FP and a stiff phase SP, characterised in that the stiff phase SP has a higher Shore hardness at body temperature than the flexible phase FP at body temperature, namely at least 15 Shore D higher.

2. The milling blank according to claim 1, wherein the flexible phase FP comprises a soft polymer A and the stiff phase SP comprises a hard polymer B.

3. The milling blank according to claim 2, wherein the flexible phase FP consists of a soft polymer A and the stiff phase SP consists of a hard polymer B.

4. The milling blank according to any of the preceding claims, wherein the stiff phase SP has a higher Shore hardness at body temperature than the flexible phase FP at body temperature, namely at least 18 Shore D higher, particularly the stiff phase SP has a higher Shore hardness at body temperature than the flexible phase FP at body temperature, namely at least 20 Shore D higher, more particularly the stiff phase SP has a higher Shore hardness at body temperature than the flexible phase FP at body temperature, namely at least 22 Shore D higher.

5. The milling blank according according to any of the preceding claims, wherein the flexible phase FP comprises a thermomemory effect.

6. The milling blank according to any of the preceding claims, wherein the soft polymer A of the flexile phase FP and the hard polymer B of the stiff phase SP is- a polymer P selected from the group consisting of polyalkyl methacrylate, polycycloalkyl methacrylate, polycycloalkyl acrylate and polyalkyl acrylate or- a polymerized component of a thermoplastic comprising a polymer P selected from the group consisting of polyalkyl methacrylate, polycycloalkyl methacrylate, polycycloalkyl acrylate and polyalkyl acrylate or at least one copolymer CP produced of at least one monomers M, particularly two monomers M, particularly selected from the group consisting of an alkyl methacrylate, an alkyl acrylate, a cycloalkyl methacrylate and a cycloalkyl acrylate, wherein the cycloalkyl methacrylate and the cycloalkyl acrylate are unsubstituted or substituted with at least one -Ci-4-alkyl, -OH or Ci-4-alcohol.

7. The milling blank according to any of the preceding claims, wherein the polymer P of the hard polymer B and / or the polymer P of the soft polymer A is selected from the group consisting of poly-Ci- -alkyl methacrylate, poly-Ci- -alkyl acrylate, poly-Ca-is-cycloalkyl methacrylate und poly-Cs-is-cycloalkyl acrylate, particularly polyethyl methacrylate (PEMA) and polymethyl methacrylate (PMMA) and / or a polyethyl methacrylate-polymethyl methacrylate copolymer (PEMA-PMMA).

8. The milling blank according to any of the preceding claims, wherein the copolymer isCP is derived from monomers M selected from the group consisting of 2- eth oxy meth aery I ate, 2-ethoxy acrylate, tetra hydrofurfuryl acrylate and tetra hydrofurfuryl methacrylate.

9. The milling blank according to any of the preceding claims, wherein the soft polymer A comprises as a polymer P at least 10 % polyethyl methacryate (PEMA), particularly 20 % polyethyl methacrylate (PEMA), more particularly the soft polymer A comprises at least 30 % polyethyl methacrylate (PEMA), wherein the soft polymer A may further comprise polymethyl methacrylate (PMMA).

10. The milling blank according to any of the preceding claims, wherein the milling blank comprises a hardness gradient in Z-direction through the flexible phase FP and the stiff phase SP.

11. The milling blank according to any of the preceding claims, wherein the Shore hardness of the flexible phase FP is between 20 Shore A and 45 Shore D at body temperature.

12. The milling blank according to any of the preceding claims, wherein the Shore hardness of the stiff phase SP is at least 60 Shore D at body temperature, particularly wherein the Shore hardness of the stiff phase SP is 60 to 95 Shore D, more particularly the Shore hardness of the stiff phase SP is 60 to 90 Shore D.

13. The milling blank according to any of the preceding claims, wherein the hardness gradient between the softest point of the flexible phase FP and the stiffest point of the stiff phase SP is at least 15 Shore D.

14. The milling blank according to any of the preceding claims, wherein the flexible phase FP and the stiff phase SP are directly connected to each other, particularly polymerised together, more particularly polymerised through pressure and heat.

15. The milling blank according to any of the preceding claims, wherein the flexible phase FP and the stiff phase SP form an equal wave like structure or a planar structure.

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