# US 8,785,008 B2 · Zirconia sintered bodies with high total light transmission and high strength, uses of the same, and process for producing the same

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- Number: US 8,785,008 B2
- Document ID: US8785008B2
- Status: Granted
- Kind: B2
- Application number: 12/375,001
- Filed: 2007-07-19
- Published: 2010-01-07
- Granted: 2014-07-22
- Earliest claimed: 2006-07-25
- Assignees: Tosoh Corporation
- Applicants: Isao Yamashita; Koji Tsukuma; Toru Tsuyoshi
- Inventors: Isao Yamashita; Koji Tsukuma; Toru Tsuyoshi
- Web page: https://patentgrep.com/patent/US8785008B2

## CPC

- C04B 35/486: Fine ceramics
- B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites
- C04B 35/6455: {Hot isostatic pressing}
- A61C 7/14: Brackets (A61C7/28 takes precedence); Fixing brackets to teeth
- A61C 13/0022: {Blanks or green, unfinished dental restoration parts}
- C04B 2235/3206: Magnesium oxides or oxide-forming salts thereof
- C04B 2235/3217: Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
- C04B 2235/3222: Aluminates other than alumino-silicates, e.g. spinel (MgAl2O4)
- C04B 2235/3225: Yttrium oxide or oxide-forming salts thereof
- C04B 2235/3246: Stabilised zirconias, e.g. YSZ or cerium stabilised zirconia
- C04B 2235/3409: Boron oxide, borates, boric acids, or oxide forming salts thereof, e.g. borax
- C04B 2235/3418: Silicon oxide, silicic acids or oxide forming salts thereof, e.g. silica sol, fused silica, silica fume, cristobalite, quartz or flint
- C04B 2235/3463: Alumino-silicates other than clay, e.g. mullite
- 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 2235/6021: Extrusion moulding
- C04B 2235/6022: Injection moulding
- C04B 2235/604: Pressing at temperatures other than sintering temperatures
- C04B 2235/656: characterised by specific heating conditions during heat treatment
- C04B 2235/6567: Treatment time
- C04B 2235/661: Multi-step sintering
- C04B 2235/72: Products characterised by the absence or the low content of specific components, e.g. alkali metal free alumina ceramics
- C04B 2235/761: Unit-cell parameters, e.g. lattice constants
- C04B 2235/762: Cubic symmetry, e.g. beta-SiC
- C04B 2235/765: Tetragonal symmetry
- C04B 2235/77: Density
- C04B 2235/785: Submicron sized grains, i.e. from 0,1 to 1 micron
- C04B 2235/786: Micrometer sized grains, i.e. from 1 to 100 micron
- C04B 2235/96: Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
- C04B 2235/9653: Translucent or transparent ceramics other than alumina
- C04B 2235/9661: Colour
- 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
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- 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)

## Abstract

The invention relates to the use of a sintered body obtained by subjecting a primary sintered body having a relative density of 95% or higher produced from a fine yttria-containing zirconia powder to HIP sintering at a temperature of 1,200-1,600° C. and a pressure of 50 MPa or higher. This sintered body is either a sintered body which has a total light transmittance, as measured at a thickness of 0.5 mm, of 43% or higher and a three-point bending strength of 1,700 MPa or higher or a zirconia sintered body which has a total light transmittance, as measured at a thickness of 1 mm, of 40% or higher and a three-point bending strength of 500 MPa or higher and which combines high strength and total light transmission.

## Claims

### Claim 1

A zirconia sintered body which comprises zirconia containing 2-4 mol % yttria and has a three-point bending strength of 1,700 MPa or higher and a total light transmittance, as measured at a thickness of 0.5 mm, of 43% or higher.

### Claim 2 (depends on 1)

The zirconia sintered body according to claim 1, which has a three-point bending strength of 1,900 MPa or higher and a total light transmittance, as measured at a thickness of 0.5 mm, of 45% or higher.

### Claim 3 (depends on 1)

The zirconia sintered body according to claim 1, characterized by being made of crystal phases which are constituted only of a fluorite structure tetragonal crystal phase (I) containing 3 mol % or less yttria or constituted of a mixed phase comprising a fluorite structure tetragonal crystal phase (I) containing 3 mol % or less yttria and a fluorite structure tetragonal crystal phase (II) containing 5 mol % or more yttria, the proportion of the fluorite structure tetragonal crystal phase (I) being 50-100%.

### Claim 4 (depends on 1)

The zirconia sintered body according to claim 1, characterized by containing no voids of 10 μm or larger and having a porosity of 0.5% or lower.

### Claim 5 (depends on 1)

A dental material comprising the zirconia sintered body according to claim 1.

### Claim 6 (depends on 1)

An orthodontic bracket comprising the zirconia sintered body according to claim 1.

### Claim 7 (depends on 1)

An artificial tooth comprising the zirconia sintered body according to claim 1.

### Claim 8 (depends on 1)

A mill blank for dental materials which comprised the zirconia sintered body according to claim 1.