# US 12,213,849 B2 · Dental zirconia blank having multilayer structure different in content of yttria

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- Number: US 12,213,849 B2
- Document ID: US12213849B2
- Status: Granted
- Kind: B2
- Application number: 16/357,373
- Filed: 2019-03-19
- Published: 2019-12-19
- Granted: 2025-02-04
- Earliest claimed: 2018-03-20
- Assignees: Shofu Inc.
- Applicants: Shofu Inc.
- Inventors: Rieko Aiba; Shuhei Takahashi; Toshio Kitamura
- Web page: https://patentgrep.com/patent/US12213849B2

## CPC

- A61C 13/0022: {Blanks or green, unfinished dental restoration parts}
- A61K 6/16: Refractive index
- A61K 6/818: comprising zirconium oxide
- A61K 6/822: comprising rare earth metal oxides
- B32B 18/00: Layered products essentially comprising ceramics, e.g. refractory products
- C04B 35/486: Fine ceramics
- C04B 35/62605: {Treating the starting powders individually or as mixtures}
- C04B 35/62645: {Thermal treatment of powders or mixtures thereof other than sintering}
- C04B 35/638: Removal thereof
- C04B 35/64: Burning or sintering processes (C04B33/32 takes precedence {; powder metallurgy B22F})
- A61C 13/082: {Cosmetic aspects, e.g. inlays; Determination of the colour (A61C19/10 takes precedence)}
- A61C 13/083: Porcelain or ceramic teeth {(A61C13/081 takes precedence; preparations A61K6/80)}
- B32B 33/00: Layered products characterised by particular properties or particular surface features, e.g. particular surface coatings; Layered products designed for particular purposes not covered by another single class
- C04B 2235/3217: Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
- C04B 2235/3224: Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
- C04B 2235/3225: Yttrium oxide or oxide-forming salts thereof
- C04B 2235/3239: Vanadium oxides, vanadates or oxide forming salts thereof, e.g. magnesium vanadate
- C04B 2235/3241: Chromium oxides, chromates, or oxide-forming salts thereof
- C04B 2235/3244: Zirconium oxides, zirconates, hafnium oxides, hafnates, or oxide-forming salts thereof
- C04B 2235/3246: Stabilised zirconias, e.g. YSZ or cerium stabilised zirconia
- C04B 2235/327: Iron group oxides, their mixed metal oxides, or oxide-forming salts thereof
- C04B 2235/3272: Iron oxides or oxide forming salts thereof, e.g. hematite, magnetite
- C04B 2235/3275: Cobalt oxides, cobaltates or cobaltites or oxide forming salts thereof, e.g. bismuth cobaltate, zinc cobaltite
- C04B 2235/5409: expressed by specific surface values
- C04B 2235/5454: nanometer sized, i.e. below 100 nm
- C04B 2235/549: the particle size being expressed by crystallite size or primary particle size
- C04B 2235/602: Making the green bodies or pre-forms by moulding
- C04B 2235/604: Pressing at temperatures other than sintering temperatures
- C04B 2235/6562: Heating rate
- C04B 2235/6565: Cooling rate
- C04B 2235/765: Tetragonal symmetry
- C04B 2235/78: Grain sizes and shapes, product microstructures, e.g. acicular grains, equiaxed grains, platelet-structures
- C04B 2235/96: Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
- C04B 2235/9638: Tolerance; Dimensional accuracy
- C04B 2235/9653: Translucent or transparent ceramics other than alumina
- C04B 2235/9661: Colour
- C04B 2237/348: Zirconia, hafnia, zirconates or hafnates
- C04B 2237/58: Forming a gradient in composition or in properties across the laminate or the joined articles
- A61C: DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE (non-driven toothbrushes A46B; {tongue scrapers A61B17/24;} preparations for dentistry A61K6/00; preparations for cleaning the teeth or mouth A61K8/00, A61Q11/00)
- A61K: PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES (devices or methods specially adapted for bringing pharmaceutical products into particular physical or administering forms A61J3/00; chemical aspects of, or use of materials for deodorisation of air, for disinfection or sterilisation, or for bandages, dressings, absorbent pads or surgical articles A61L; soap compositions C11D)
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE

## Abstract

To provide a dental zirconia blank which has high permeability, can reproduce a color tone close to a natural tooth and a strength to be able to tolerate in oral cavity. Furthermore, to provide a dental zirconia blank from which a prosthesis device of 4 or more units having high strength can be prepared. To provide a dental zirconia blank having a plurality of layers, comprising; a first layer consisting of a high permeability ceramic containing 91.6 to 96.5 mol % of zirconium oxide and 3.5 to 8.4 mol % of yttrium oxide, and a second layer consisting of a low permeability ceramic containing 95.6 to 98.5 mol % of zirconium oxide and 1.5 to 4.4 mol % of yttrium oxide, wherein a content rate of yttrium oxide in the low permeability ceramic is lower than a content rate of yttrium oxide in the high permeability ceramic by 0.5 to 5.4 mol %, and the first layer is positioned at one end of the plurality of layers in a layering direction.

## Claims

### Claim 1

A dental zirconia blank consisting of;
a first layer consisting of a high permeability ceramic containing 91.6 to 96.5 mol % of zirconium oxide and 3.5 to 8.4 mol % of yttrium oxide, and
a second layer consisting of a low permeability ceramic containing 95.6 to 98.5 mol % of zirconium oxide and 1.5 to 4.4 mol % of yttrium oxide, wherein
a content rate of yttrium oxide in the low permeability ceramic is lower than a content rate of yttrium oxide in the high permeability ceramic by 0.5 to 5.4 mol %,
a ceramic powder constituting the high permeability ceramic and a ceramic powder constituting the low permeability ceramic have BET specific surface areas within a range of 5 to 20 m2/g, and
the ceramic powder constituting the high permeability ceramic and the ceramic powder constituting the low permeability ceramic have average primary particle diameters within a range of 10 to 1000nm.

### Claim 2 (depends on 1)

The dental zirconia blank according to claim 1, wherein
the first layer consists of a plurality of high permeability layered areas having different compositions with each other.

### Claim 3 (depends on 2)

The dental zirconia blank according to claim 2, wherein
the first layer consists of a plurality of high permeability layered areas having different content rates of zirconium oxide and/or different content rates of yttrium oxide in the high permeability ceramic with each other.

### Claim 4 (depends on 2)

The dental zirconia blank according to claim 2, wherein
at least one high permeability layered area includes 0.0001 to 0.30 mol % of erbium oxide.

### Claim 5 (depends on 1)

The dental zirconia blank according to claim 1, wherein
the second layer consists of a plurality of low permeability layered areas having different compositions with each other.

### Claim 6 (depends on 5)

The dental zirconia blank according to claim 5, wherein
the second layer consists of a plurality of low permeability layered areas having different content rates of zirconium oxide and/or different content rates of yttrium oxide in the low permeability ceramic with each other.

### Claim 7 (depends on 5)

The dental zirconia blank according to claim 5, wherein
at least one low permeability layered area includes 0.0001 to 0.30 mol % of erbium oxide.

### Claim 8 (depends on 1)

The dental zirconia blank according to claim 1, wherein
the high permeability ceramic is a temporary calcined body of a plurality of powders having different compositions with each other.

### Claim 9 (depends on 1)

The dental zirconia blank according to claim 1, wherein
the low permeability ceramic is a temporary calcined body of a plurality of powders having different compositions with each other.

### Claim 10 (depends on 1)

The dental zirconia blank according to claim 1, wherein
the first layer is positioned to a position spaced from a surface of a side of one end in a layering direction by a range of 5 to 40% of a dimension between the surface of the side of the one end and a surface of a side of the other end opposing to the surface of the side of the one end on a perpendicular line from the center of the gravity of the surface of the side of the one end at which the first layer is positioned in the layering direction of the dental zirconia blank.

### Claim 11 (depends on 1)

The dental zirconia blank according to claim 1, wherein
a difference of BET specific surface area between the ceramic powder constituting the high permeability ceramic and the ceramic powder constituting the low permeability ceramic is within a range of 2 m2/g and a difference of an average primary particle diameter between the ceramic powder constituting the high permeability ceramic and the ceramic powder constituting the low permeability ceramic is within a range of 20 nm.

### Claim 12 (depends on 2)

The dental zirconia blank according to claim 2, wherein
transparency of at least one high permeability layered area is higher than transparency of the second layer, and
the chromaticities LE, aE, bE of the at least one high permeability layered area based on the L*·a*·b* colorimetric system satisfy the following relations:
65.0≤LE≤82.0
−4.0≤aE≤2.0
0.0≤bE≤20.0.

### Claim 13 (depends on 1)

The dental zirconia blank according to claim 1, wherein
transparency of the first layer is higher than transparency of the second layer, and
the chromaticities LE, aE, bE of the first layer based on the L*·a*·b* colorimetric system satisfy the following relations:
65.0≤LE≤82.0
−4.0≤aE≤2.0
0.0≤bE≤20.0.

### Claim 14 (depends on 1)

The dental zirconia blank according to claim 1, wherein
the high permeability ceramic includes 0.0001 to 0.30 mol % of erbium oxide.

### Claim 15 (depends on 1)

The dental zirconia blank according to claim 1, wherein
the low permeability ceramic includes 0.0001 to 0.30 mol % of erbium oxide.

### Claim 16 (depends on 1)

The dental zirconia blank according to claim 1, wherein
the first layer consists of a plurality of high permeability layered areas having different compositions with each other, and
the second layer consists of a plurality of low permeability layered areas having different compositions with each other.

### Claim 17 (depends on 1)

The dental zirconia blank according to claim 1, wherein
the first layer consists of a plurality of high permeability layered areas having different content rates of zirconium oxide and/or different content rates of yttrium oxide in the high permeability ceramic with each other, and
the second layer consists of a plurality of low permeability layered areas having different content rates of zirconium oxide and/or different content rates of yttrium oxide in the low permeability ceramic with each other.