Multi sectional dental zirconia milling block, process of production and use thereof

1. A porous dental milling block comprising at least two geometrically defined Material Sections A and B,

Material Section A comprising a tetragonal zirconia crystal phase in an amount A-T in wt.-% and a cubic zirconia crystal phase in an amount A-C in wt.-%,

Material Section B comprising a tetragonal zirconia crystal phase in an amount B-T in wt.-% and a cubic zirconia crystal phase in an amount B-C in wt.-%,

wherein

(amount of tetragonal phase A - T in wt.-%)/(amount of cubic phase content A - C in wt.-%)>1

and

(amount of tetragonal phase content B - T in wt.-%)/(amount of cubic phase content B - C in wt.-%)<1,

the material of Material Sections A and B showing a N 2 adsorption and/or desorption behaviour of isotherm IV according to IUPAC classification.

2. The porous dental milling block of claim 1 , the material of Material Sections A and B having the following property:

the sintering temperature being in a range of 1200 to 1400° C.

3. The porous dental milling block of claim 1 having at least one of the following features:

the ratio of the tetragonal phase content A-T in % to the cubic phase content A-C in % in Section A being in a range from about 1.2 to about 50,

the ratio of the tetragonal phase content B-T in % to the cubic phase content B-C in % in Section B being in a range from about 0.02 to about 0.8.

4. The porous dental milling block of claim 1 having at least one of the following features with respect to Material Section A before sintering to final density:

showing a N 2 adsorption and desorption behaviour with a hysteresis loop of type H1 according to IUPAC classification;

showing a N 2 adsorption and desorption behaviour with a hysteresis loop in a p/p0 range of 0.70 to 0.95;

average connected pore diameter: from about 10 to about 100 nm;

average grain size of crystalline zirconia: less than about 100 nm;

BET surface: from about 10 to about 200 m 2 /g;

Biaxial flexural strength: from about 10 to about 40 MPa;

x, y, z dimension: at least about 5 mm;

Vickers hardness: from about 25 (HV 0.5) to about 150 (HV 1);

having an isotropic sintering behaviour;

density: 2.2 to 3.3 g/cm 3 ;

sintering temperature: from about 1200 to about 1400° C.;

having an ZrO 2 content: from about 85 to about 98 mol %;

having a HfO 2 content: from about 0 to about 3 mol %;

having an Y 2 O 3 content: from about 1 to about 15 mol %;

having an Al 2 O 3 content: from about 0 to about 1 mol %.

5. The porous dental milling block of claim 4 further having at least one of the following features with respect to Material Section A before sintering to final density:

average connected pore diameter: from about 10 to about 80 nm;

Biaxial flexural strength: from about 15 to about 30 MPa;

x, y, z dimension: at least about 10 mm.

6. The porous dental milling block of claim 5 further having at least one of the following features with respect to Material Section A before sintering to final density:

average connected pore diameter: from about 10 to about 50 nm;

x, y, z dimension: at least about 20 mm.

7. The porous dental milling block of claim 1 having at least one of the following features with respect to Material Section B before sintering to final density:

showing a hysteresis loop when analyzed with regard to its adsorption and desorption behaviour to nitrogen;

showing a N 2 adsorption and desorption behaviour with a hysteresis loop of type H1 according to IUPAC classification;

showing a N 2 adsorption and desorption behaviour with a hysteresis loop in a p/p0 range of 0.70 to 0.95;

average connected pore diameter: from about 10 to about 100 nm;

average grain size of crystalline zirconia: less than about 100 nm;

BET surface: from about 10 to about 200 m 2 /g;

Biaxial flexural strength: from about 10 to about 40 MPa;

x, y, z dimension: at least about 5 mm;

Vickers hardness: from about 25 (HV 0.5) to about 150 (HV 1);

having an isotropic sintering behaviour;

density: 2.2 to 3.3 g/cm 3 ;

sintering temperature: from about 1200 to about 1400° C.;

having an ZrO 2 content: from about 85 to about 98 mol %;

having a HfO 2 content: from about 0 to about 3 mol %;

having an Y 2 O 3 content: from about 1 to about 15 mol %;

having an Al 2 O 3 content: from about 0 to about 1 mol %.

8. The porous dental milling block of claim 7 further having at least one of the following features with respect to Material Section B before sintering to final density:

average connected pore diameter: from about 10 to about 80 nm;

Biaxial flexural strength: from about 15 to about 30 MPa;

x, y, z dimension: at least about 10 mm.

9. The porous dental milling block of claim 8 further having at least one of the following features with respect to Material Section B before sintering to final density:

average connected pore diameter: from about 10 to about 50 nm;

x, y, z dimension: at least about 20 mm.

10. The porous dental milling block of claim 1 , Material Section A and Material Section B having the shape of layers or blocks; being arranged in a core-shell structure; having tooth-like shapes; or a combination thereof.

11. The porous dental milling block of claim 1 not comprising oxides selected from TiO 2 , SiO 2 or mixtures thereof in an amount above 2 mol % with respect to the weight of the porous dental milling block.

12. The porous dental milling block of claim 1 comprising means for attaching it to a machining device, the means for attaching being selected from grooves, notches, recesses, stamps and holding devices, stumps and combinations thereof.