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    • 专利摘要:
    the present invention relates to dental zirconia ceramics presenting opalescence and having a grain size in the range of 10 nm to 300 nm, a density of at least 99.5% of the theoretical density, a transmittance of visible light equal to or greater than than 45% at 560 nm, and a resistance of at least 800 mpa.
    公开号:BR112015032559B1
    申请号:R112015032559-9
    申请日:2014-06-12
    公开日:2020-06-16
    发明作者:Dmitri G. Brodkin；Yijun Wang；Ling Tang；Ajmal Khan；Anna B. Verano
    申请人:Ivoclar Vivadent, Inc.；
    IPC主号:
    专利说明:

    Descriptive Report on the Invention Patent for ZIRCONIA DENTAL CERAMICS, DENTAL ARTICLE, AND ITS MANUFACTURING METHOD.
    CROSS REFERENCE TO RELATED REQUESTS
    [001] This application claims priority for United States Patent Application Number 61/840055, filed on June 27, 2013, entitled Nanocrystalline Zirconia And Methods Of Processing Thereof (NT: Nanocrystalline Zirconia And Processing Methods Thereof), whose description is incorporated here, in this patent application, by reference in its entirety.
    TECHNICAL FIELD
    [002] The present invention relates to dental restorations comprising nanozirconia and methods of processing it, and more particularly to dental nanozirconia ceramics combining translucency that equals glass ceramics, opalescence simulating the natural dentition and high resistance characteristics of tetragonal zirconia.
    BACKGROUND
    [003] Currently, the best commercially available full-grain (monolithic) zirconia dental ceramic materials are aesthetically inferior to leucite or lithium disilicate glass ceramic materials like IPS e.max or IPS Empress due to less translucency and the lack of opalescence. Better light transmittance and better opalescence are required to better simulate the natural dentition. Humane enamel has variable anisotropic translucency which introduces many optical effects that are difficult to replicate with ceramic material. Opalescence is an optical characteristic of natural enamel that can create a highly complex visual display. So far, only glass ceramic materials have come close to duplicating such a complex.
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    2/33 optics of natural dentition including opalescence. At the same time, glass ceramic materials are not as strong as zirconia materials, thus limiting their clinical use to single and multi-unit restorations and cases without bruxism.
    [004] United States Patent No. 8,309,015, which is hereby incorporated by reference in its entirety, refers to a tetragonal nanozirconia processing method with grain sizes below 100 nm. The sintered structure is claimed to only contain pores smaller than about 25 nm. The method lacks mass consolidation technology and does not address, mention or discuss opalescence. Instead, the requirements stipulated in the patent and claims include the diameter of any pores which are present in the sintered translucent zirconia structure to be no more than about 25 nm, which, as is believed, would exclude this material from be in the desired opalescent range as taught in the present invention and is also unrealistic for any practical mass consolidation technology for producing dental articles through pressure-free sintering.
    [005] United States Patent No. 8,598,058, which is hereby incorporated by reference in its entirety, refers to a method of processing nanozirconia articles with grain sizes below 200 nm and pore size below 50 nm comprising from about from 0.5% to about 5.0% of the lanthanum oxide claimed to be essential to obtain the claimed properties. Again, this patent does not deal with, mention or discuss opalescence despite showing sintered structures illuminated with incident light through which opalescence would be obvious if present.
    [006] United States Patent No. 7,655,586 and No.
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    7,806,694, both incorporated by reference in its entirety, refer to a dental article and manufacturing methods comprising: a tetragonal zirconia ceramic material stabilized with single component yttrium having grains of average grain size exceeding 100 nanometers and not exceeding about 400 nanometers, in which the ceramic material is made of particulate material consisting essentially of ceramic crystallites with an average size of less than about 20 nm; wherein the particulate material is sintered without applying external pressure at a temperature of less than about 1300 ° C for a total density in which the final pore size does not exceed the size of the ceramic crystallite size; and wherein the ceramic material exhibits at least 30% relative transmission of visible light when measured through a thickness of about 0.3 to about 0.5 mm. Again the requirements stipulated in the patents and claims limit the pore diameter and obtainable grain size distributions which are present in the sintered translucent zirconia structure, which, it is believed, would exclude this material from being opalescent.
    [007] The following published patents and patent applications, directed to zirconia ceramics or processing methods, are hereby incorporated by reference in their entirety: US 6,787,080, US 7,655,586, US 7,806. 694 US 7,833,621, US 7,674,523, US 7,429,422, US 7,241,437, US 6,376,590, US
    6,869,501, US 8,298,329, US 7,989,504, US 8,425,809, US 8,216,439, US 8,309,015, US 7,538,055, US 4,758,541, US 2011/0027742, US 2012/0058883, US 2010/0003630, US 2009/0274993, US
    2009/0294357, US 2009/0115084, US 2011/0230340, US
    2009/0004098, US 2010/0075170, US 2004/0222098, and US 2013/0313738. Between these US 8,298,329 and US 2013/0313738 descre
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    4/33 comes translucent nano-crystalline dental ceramics and a manufacturing process by slipcasting or powder compaction.
    [008] The following publications refer to the processing and properties of zirconia ceramics or transparent alumina.
    [009] Adam, J., et al. Milling of Zirconia Nanoparticles in a Stirred
    Media Mill, J. Am. Ceram. Soc., 91 [9] 2836-2843 (2008)
    [0010] Alaniz, J. E., et al. Optical Properties of Transparent Nanocrystalline Yttria Stabilized Zirconia, Opt. Mater., 32, 62-68 (2009) [0011] Anselmi-Tamburini, et al. Transparent Nanometric Cubic and Tetragonal Zirconia Obtained by High-Pressure Pulsed Electric Current Sintering, Adv. Funct. Mater. 17, 3267-3273 (2007)
    [0012] Apetz, R., et al. Transparent Alumina: A Light Scattering
    Model, J. Am. Ceram. Soc., 86 [3], 480-486 (2003)
    [0013] Binner, J., et al. Processing of Bulk Nanostructured Ceramics, J. Eur. Ceram. Soc. 28, 1329-1339 (2008)
    [0014] Binner, J. et al. Compositional Effects in Nanostructured
    Yttria Partially Stabilized Zirconia Int. J. Appl. Ceram. Tec., 8, 766-782 (2011)
    [0015] Casolco, S.R. et al. Transparent / translucent polycrystalline nanostructured yttria stabilized zirconia with varying colors Scripta Mater. 58 [6], 516-519 (2007)
    [0016] Garcia, et al. Structural, Electronic, and Optical Properties of ZrO2 from Ab Initio Calculations, J. Appl. Phys., 100 [1], 104103 (2006)
    [0017] Klimke, et al. Transparent Tetragonal Yttria-Stabilized Zirconia Ceramics J. Am. Ceram. Soc., 94 [6] 1850-1858 (2011)
    [0018] Knapp, K. Understanding Zirconia Crown Esthetics and
    Optical Properties, Inclusive Magazine, (2011)
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    [0019] Rignanese, et al, First-principles Study of the Dynamical and Dielectric Properties of Tetragonal Zirconia Phys. Rev. B, 64 [13], 134301 (2001)
    [0020] Srdic, V. V., et al. Sintering Behavior of Nanocrystalline Zirconia Prepared by Chemical Vapor Synthesis J. Am. Ceram. Soc. 83 [4], 729-736 (2000)
    [0021] Srdic, V. V., et al. Sintering Behavior of Nanocrystalline Zirconia Doped with Alumina Prepared by Chemical Vapor Synthesis J. Am. Ceram. Soc. 83 [8], 1853-1860 (2000)
    [0022] Trunec, et al. Compaction and Presureless Sintering of Zirconia Nanoparticles J. Am. Ceram. Soc. 90 [9] 2735-2740 (2007)
    [0023] Vladimir V. Srdic ', Markus Winterer, and Horst Hahn. Sintering Behavior of Nanocrystalline Zirconia Prepared by Chemical Vapor Synthesis. J. Am. Ceram. Soc., 83 [4] 729-36 (2000)
    [0024] Most or all of the patents and patent publications listed above describe a variety of properties of tetragonal nanozirconia materials and methods of processing them. All of these sources seem to describe sintering with the application of external pressure such as HIP or SPS.
    [0025] Light transmission at about 550 to 560 nm is commonly accepted to compare the light transmittance of dental materials, especially zirconia dental materials, which is related to color resolution / photopic vision sensitivity of the eyes humans. In humans, photopic vision allows color perception, mediated by cone cells in the retina. The human eye uses three types of cones to feel light in three bands of color. The cone's biological pigments have maximum absorption values at wavelengths of about 420 nm (bluish violet), 534 nm (bluish green), and 564 nm (yellowish green). Its sensitivity ranges overlap to provide vision across the spec
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    6/33 visible from about 400 nm to about 700 nm. Colors are perceived when the cones are stimulated, and the perceived color depends on how much each type of cone is stimulated. The eye is more sensitive to green light (555 nm) because green stimulates two of the three types of cones almost equally; therefore, light transmission at 560 nm is used as a basis for the characterization of the highly translucent zirconia materials of the present invention.
    [0026] Opalescence is one of the important optical characteristics of natural dentition that is crucial to replicate in aesthetic dental restoration material in order to manufacture natural dental restorations. This aesthetic requirement is often referred to as the vitality of a restoration. It is an optical effect of general knowledge resulting in a bluish appearance in the reflected color and an orange / brown appearance in the transmitted color. The opalescent property is usually associated with the dispersion of the shortest wavelengths of the visible spectrum, by inclusions of the second phase (s) having a different refractive index than the matrix phase. In human teeth, the opalescence of natural enamel is related to the dispersion of light and the dispersion produced by the complex spatial organization of the elemental constituents of enamel - hydroxyapatite nanocrystals. The hydroxyapatite crystallites that form the human enamel are arranged in bundles or leaves forming rods (bundles) and interbastonetes (leaves), which are organized in a honeycomb-like structure. The average crystal size is 160 nm long and 20 to 40 nm wide. As light passes through the enamel, the rods disperse and transmit the light at shorter wavelengths, making the enamel opalescent.
    [0027] The degree of opalescence can be quantified by a measurement by colorimetric spectrophotometry with a CIE standard. Per
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    7/33 example, Lee et al. (see references below) use the Opalescence Parameter (OP) as a measure of opalescence. Kobashigawa et. al. (United States Patent No. 6,232,367) use the same basic formula, but have called it the Chromaticity Difference. The opalescence parameter (OP or Chromaticity Difference) is calculated according to the following formula:
    OP = [(ASIC -CIEa T * R *) 2 + (CIEbT -CIEbR * *) 2] 1/2, wherein (CIEaT -ciEa * R *) is the difference between modes of transmission and reflectance coordinate red-green colors to *; (ClEb T * -ciEb R *) is the difference between the modes of transmission reflectance in the yellow-blue coordinate b *. Using this formula, the current commercially available translucent zirconia OP is calculated to be in the range from about 5 to about 7. These commercial materials are clearly non-opalescent. According to data in the literature, it is believed that materials with low OP values are not opalescent. The OP range measured for clearly opalescent human enamel was 19.8 to 27.6. According to Kobashigawa, to correspond to the vitality of natural teeth, the OP value must be at least 9, and preferably higher, so that the opalescence effect is clearly observed. On the other hand, it is not useful to equate high OP values of human enamel just by numbers since the restoration will not mix well with the adjacent teeth in the patient's mouth.
    [0028] The following publications refer to opalescence mechanisms in natural or synthetic materials.
    [0029] Cho, M.-S. et al. Opalescence of all-ceramic core and veneer materials, Dental Materials, 25, 695-702, (2009)
    [0030] Egen, M. et al. Artificial Opals as Effect Pigments in ClearCoatings, Macromol. Mater. Eng. 289, 158-163, (2004)
    [0031] Lee, Y.-K., et al. Measurement of Opalescence of Resin
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    Composites, Dental Materials 21, 1068-1074, (2005)
    [0032] Lee, Y.-K., et al. Changes in Opalescence and Fluorescence Properties of Resin Composites after Accelerated Aging, Dental Materials 22, 653-660, (2006)
    [0033] Lee, Y.-K., Influence of Scattering / Absorption Characteristics on the Color of Resin Composites Dental Materials 23, 124-131, (2007)
    [0034] Lee, Y.-K., Measurement of Opalescence of Tooth Enamel, Journal of Dentistry 35, 690-694, (2007)
    [0035] Kobashigawa, A. I. et al., Opalescent Fillers for Dental
    Restorative Composites, US patent 6,232,367 B1, (2001)
    [0036] Peelen. J. G. J. et al. Light Scattering by Pores in Polycrystalline Materials: Transmission Properties of Alumina, Journal of Applied Physics, 45, 216-220, (1974)
    [0037] Primus, C. M., et al. Opalescence of Dental Porcelain
    Enamels Quintessence International, 33, 439-449, (2002)
    [0038] Yu, B., et al. Difference in Opalescence of Restorative Materials by the Illuminant, Dental Materials 25, 1014-1021, (2009)
    [0039] White et al., Biological Organization of Hydroxyapatite Crystallites into a Fibrous Continuum Toughens and Controls Anisotropy in Human Enamel, J Dent Res 80 (1): 321-326, (2001).
    [0040] It would be extremely beneficial to have high translucency of glass ceramics combined with high strength of tetragonal zirconia and opalescence simulating natural dentition in the same sinterizable dental restoration material below 1200 ° C, which can be processed in a zirconia restoration of complete contour using conventional techniques and equipment such as dental CAD / CAM systems, dental pressing furnaces and dental furnaces. Other techniques and equipment used successfully in other technology areas can also be used to
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    9/33 mass production of molded parts and almost liquid components.
    SUMMARY
    [0041] These and other characteristics are obtained by the nanozirconia structures of the present invention. In one embodiment, certain ranges of processing conditions are used to produce nanozirconia structures that are green, brown (pre-sintered) opalescent and fully dense condition as shown in Figure 2. The opalescent nanozirconia structures can also be almost transparent or highly translucent at all stages of processing (visible light transmittance equal to or greater than 45% and preferably greater than 50% at 560 nm for 1 mm samples) and result in fully dense tetragonal zirconia structures (density of at least 99.5% or higher and preferably> 99.9% dense) which in addition to high light transmittance also comprise high resistance (resistance of at least 800 MPa or higher and preferably> 1200 MPa resistance) and sinterability at temperatures below 1200 ° C in conventional dental ovens which is especially important for dental restoration applications.
    [0042] Figure 1 shows the spectral dependence (wavelength) of light transmittance within the visible light range from 400 to 700 nm for a variety of dental materials including the state-of-the-art commercial translucent zirconia marks manufactured from from Zpex ™ and Zpex ™ Smile powders produced by Tosoh (Japan). The light transmittance of materials produced from Zpex ™ and Zpex ™ Smile measured at 560 nm, the wavelength of visible light of the highest physiological importance mentioned above, is 39% and 46%, respectively for 1 mm samples. The difference in light transmittance between Zpex ™ and Zpex ™ samples
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    Smile is related to its content of Yttria (Y2O3) and the composition of the resulting phase: while zirconia produced from Zpex ™ comprising 3% in moles of Y2O3 is tetragonal, zirconia produced from Zpex Smile (~ 5.3% in moles of Y2O3) comprises both tetragonal and cubic phases, so it is more translucent but only half as strong as tetragonal zirconia (~ 1200 MPa vs ~ 600 MPa, respectively). Both materials as well as other commercial zirconia materials are clearly non-opalescent.
    [0043] Comparing the curves shown in Figure 1, it becomes evident that opalescent nanozirconia materials of the present invention have more pronounced spectral transmittance curves as measured in the transmittance mode by a conventional visible light spectrophotometer equipped with an integrating sphere. This is consistent with the fact that, being opalescent, the nanozirconia materials of the present invention spread blue light, that is, shorter wavelengths, preferably, while allowing yellowish red light, that is, longer wavelengths. , transmit through with limited dispersion. In this way, it allows us to define its advantageous light transmittance properties as being greater than 45% and preferably greater than 50% over the entire spectral range from 560 nm to 700 nm for naturally shaded or colored nanozirconia and greater than than 35% and preferably greater than 40% over the entire spectral range from 560 nm to 700 nm for shaded nanozirconia intentionally doped with coloring ions such as Fe, Cr, Ni, Co, Er, Mn and other listed ions / oxides United States Patent Nos .: 6,713,421 and 8,178,012, which are hereby incorporated by reference in their entirety. Typically, the light transmittance of shaded zirconia is 5 to 10% less than the light transmittance of non-shaded or naturally colored zirconia.
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    [0044] In the tetragonal nanozirconia of the present invention, opalescence is believed to come from the interaction of visible light with the specific crystalline structure and grain / pore size distributions. In particular, we speculate that dispersion occurs essentially due to the existence of residual pores and / or birefringence dependent on the size of the grains and the associated differences in the refractive index between the pores and the tetragonal zirconia matrix or between different crystallographic orientations in a structure of individual nanozirconia crystallites. In this complex optical phenomenon or combination of optical phenomena resulting in opalescence, both the total porosity and the pore size distribution will affect the dispersion related to the pores in all stages of the processing of nanozirconia from green to brown to sintered structures; at the same time, the contribution of birefringence intrinsic to tetragonal zirconia is dependent on the size distribution of grains in partially or fully sintered structures. Normally, the pore and grain sizes in well-formed nanozirconia compacts are of the same scale and increase concomitantly with densification and grain growth. The desired level of opalescence exists only for combining specific porosity, and pore / grain size distributions. The selective dispersion of only short wavelengths of visible light is the key to achieving a combination of optical opalescence and a high level of translucency. It can be speculated that one of the applicable dispersion models is Rayleigh dispersion, in which the size of the dispersion species is much smaller than the incident wavelength, the intensity of the dispersion (I) is strongly dependent on the wavelength, and the intensity spread over both the forward and backward directions are equal for a specific wavelength. According to the
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    12/33 Rayleigh's dispersion theory, the fact that the cross section of the dispersion σs is proportional to λ 4 , where λ is the wavelength of the incident light explains why the shorter wavelengths (blue) are spread more strongly longer wavelengths (red). For example, the same nanoscale dispersion center / site will spread a wavelength at 430 nm (in the blue range) by a factor of 6 times more efficiently compared to a wavelength of 680 nm (in the red range). As a result, an observer will find that the samples appear bluish in color when viewed from the same side of the light source whereas they appear yellowish and reddish in color when viewed from the opposite side of the light source. This unique feature of the nanozirconia materials of the present invention occurs only for specific processing methods and starting materials described below resulting in similar grain and pore size distributions during a transition from a transparent stage to a translucent within the full range of grain sizes from 10 nm to 300 nm and final pore size mostly greater than 25 nm, and preferably greater than 30 nm with total porosity being less than 0.5% and preferably less than 0.1% (in fully dense nanozirconia structures). The average grain size in the translucent opalescent zirconia of the present invention as measured according to the test method ASTM E112 - 12 is 40 nm to 150 nm, preferably 50 to 100 nm, and most preferably 50 at 80 nm.
    [0045] The materials of the present invention are especially useful for full contour restorations combining the strength of zirconia with the aesthetics of glass ceramic reference standards.
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    [0046] In various modalities, dental restorations comprising opalescent nanozirconia can be molded by grinding, injection molding, electrophoretic deposition, gel casting, etc.
    [0047] The opalescent nanozirconia dental restorations of the present invention comprise the following main characteristics:
    [0048] Opalescents with OP values above 9 and preferably above 12.
    [0049] Almost transparent or highly translucent in shaded or non-shaded (natural) condition: Light transmittance of at least 45% and preferably greater than 50% at a wavelength of 560 nm or even across the spectral range from 560 nm to 700 nm for non-shaded or naturally colored nanozirconia for 1 mm samples; and greater than 35% and preferably greater than 40% at 560 nm or even over the entire spectral range from 560 nm to 700 nm for shaded nanozirconia intentionally doped with dye ions for 1 mm samples.
    [0050] Predominantly tetragonal, that is, the main phase is tetragonal zirconia (less than 10% cubic) and preferably YTZP, that is, Yttria Stabilized Tetragonal Zirconia Polycrystal Polycrystal with Y2O3 content inside from 0 to 3 mol%.
    [0051] Grain size within the general range from 10 nm to 300 nm, or from 20 nm to 250 nm, in a fully sintered condition as confirmed by fracture surface analysis (see representative fracture surface in Figures 11A, 11B and 11C ).
    [0052] The average grain size in the translucent opalescent zirconia of the present invention as measured according to the test method ASTM E112 (or EN 623-3) is 40 nm to 150 nm, so
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    14/33 preferably from 50 to 100 nm, and most preferably from 50 to 80 nm.
    [0053] Pore size mostly greater than 25 nm, preferably 30 nm when the density is greater than 99.5%. Most preferably, the porosity is less than 0.1% (density> 99.9% of theoretical density) for maximum transmittance of visible light.
    [0054] Strong - ISO 6872 flexural strength of at least 800
    MPa or higher, and preferably> 1200 MPa resistance; and most preferably> 2 GPa of resistance.
    [0055] Sinterable at temperatures <1200 ° C using conventional dental ovens or dental microwave ovens.
    [0056] Molded by CAD / CAM, EPD, LPIM, dental thermal pressing (such as glass ceramic ingots) similar to LPIM and gel casting using RP molds.
    [0057] Zirconia can include a stabilizing additive selected from Y, Ce, Mg, or mixtures thereof, or another known stabilizing additive.
    [0058] The numbers and ranges in the specification and in the claims can cover values obtained by applying the regular rounding rules and / or up to +/- 5%.
    BRIEF DESCRIPTION OF THE DRAWINGS
    [0059] The modalities of the present invention will be more fully understood and appreciated through the Detailed Description that follows together with the attached drawings, in which:
    [0060] Figure 1 shows the spectral dependence (wavelength) of light transmittance within the visible light range from 400 to 700 nm for a variety of dental materials including the current state of the art translucent zirconia marks
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    15/33 manufactured from Zpex ™ and Zpex ™ Smile powders produced by Tosoh (Japan).
    [0061] Figure 2 shows the transition of tetragonal nanozirconia material of this invention from an almost transparent green stage to a totally dense translucent.
    [0062] Figures 3A and 3B compare the light transmittance and opalescence of the nanozirconia materials of the present invention in green, brown and totally dense condition with commercial dental zirconia materials in a totally dense condition.
    [0063] Figure 4 shows a generic spreadsheet of the processing method of the present invention.
    [0064] Figure 5 shows a spreadsheet of a modality of the process according to the present invention.
    [0065] Figure 6 shows a veneer made of fully dense nanozirconia of the present invention showing clearly visible opalescence.
    [0066] Figure 7 shows a microstructure of 99.9% dense opalescent nanozirconia structure with average grain size of 136 nm sintered in a conventional dental oven according to the present invention as described in Example 1A.
    [0067] Figure 8 shows a microstructure of 99.9% dense opalescent nanozirconia structure with average grain size of 112 nm sintered in a conventional dental oven according to the present invention as described in Example 1C.
    [0068] Figure 9 shows a microstructure of 99.9% dense opalescent nanozirconia structure with average grain size of 108 nm sintered in a conventional dental oven according to the present invention as described in Example 2A with a pore of at least 35 nm marked on the SEM micrograph.
    [0069] Figure 10 shows a microstructure of na structure
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    16/33 99.9% dense opalescent walnut with average grain size of 91 nm sintered in a hybrid microwave oven according to the present invention as described in Example 4B.
    [0070] Figures 11A, 11B and 11C show fracture surfaces of some of the nanozirconia materials of the present invention in several enlargements illustrating the typical grain size range and occasional nanopores with measurements ranging from 30 nm to 100 nm.
    [0071] Figure 12 shows the transition from transparent to opaque nanozirconia structures produced from suspension of ZrO2 nanoparticles based on organic solvent without Y2O3 or any other tetragonal phase stabilizer.
    [0072] Figure 13A shows the particle size distribution of concentrated nanozirconia suspension up to ~ 17% by volume of suspension at 4.5% by volume before (1) and after friction milling (2).
    [0073] Figure 13B shows the particle size of ~ 17% by volume nanozirconia suspension as received before (1) and after friction grinding (2).
    DETAILED DESCRIPTION
    [0074] Surprisingly it was found that within a certain range of processing conditions and starting particle sizes, the resulting nanozirconia structures are opalescent in green, brown (or pre-sintered) and, most importantly, in totally dense. Opalescent nanozirconia structures can also be almost transparent or highly translucent at all stages of processing and result in totally dense structures (in> 99.5% dense) which in addition to high light transmittance also comprise high resistance (> 800 MPa and even in excess of 2 GPa) and sinterizable at temperatures below 1200 ° C in conventional dental ovens, which is especially important
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    17/33 tant for dental restoration applications. The materials of the present invention are especially useful for full-contour restorations combining the strength of zirconia with the aesthetics of glass ceramic reference standards. Dental restorations comprising opalescent nanozirconia can be shaped by machining / grinding, injection molding, dental thermal pressing, electrophoretic deposition, gel casting and other dental technologies or technologies used in general industry for modeling high performance ceramics. Specifically, empty spaces by CAD / CAM can be formed by slip casting (coarse nanoparticles only), centrifugal casting, drip casting, injection molding, filter pressing and electrophoretic deposition (EPD).
    [0075] It is believed that it is the pore size distribution and / or the specific grain size distribution that make predominantly the single phase tetragonal zirconia of this invention both highly translucent and opalescent. We speculate that, in order to generate opalescence in a totally dense nanozirconia, at least one portion, preferably a larger portion of the dispersion species (for example, tetragonal grains with anisotropic refractive index and occasional nanopores) form some kind of sub - optical structure and has a characteristic size or diameter within a specific, reasonably narrow range. Within this range, the dispersion species are large enough to cause adequate dispersion of blue light but small enough not to cause much dispersion of yellow-red light, which can be explained by the Rayleigh dispersion model. Rayleigh's approximation is generally applicable to dispersion species much smaller than the wavelength of light or specifically for birefringence effects when the size of
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    18/33 tetragonal grains is at least an order of magnitude less than the wavelength of visible light. Mie's model is not restricted by grain size. Both models coincide when the grain size is less than 50 nm. Maximized opalescence will be obtained when the dispersion species present are around or just below the transitional sizes between the Rayleigh model and the Mie model (where these models start to diverge). Additionally, it can be speculated that once its size exceeds the transitional range, the opalescence effect will largely disappear the less the wavelength-dependent Mie dispersion mechanism is operational. This upper size limit for opalescence is dictated by differences in the refractive index between the pores and the tetragonal zirconia matrix and / or between different crystallographic orientations in a crystal structure of individual nanozirconia crystallites. In addition, another crucial factor that imposes an upper limit on the size of dispersion species (most grains since residual porosity is minimal) is the high translucency required for aesthetic dental ceramics. In addition, the shading of nanozirconia invariably further reduces the transmittance of total visible light by imposing additional restrictions on the grain size distribution in order to obtain the same light transmittance. Typically the light transmittance of shaded zirconia is about 5 to 10% less than the light transmittance of non-shaded or naturally colored zirconia.
    [0076] The opalescence and other physical properties of the materials of the present invention can be quantified within the following ranges:
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    19/33
    Property Wide Range Preferred Range Phase composition and chemistry Predominantly tetragonal zirconia with less than 15% combined monoclinic and cubic phase. YTZP (yttria-stabilized tetragonal zirconia polycrystalline) with 0 to 3 moles% Y2O3 Opalescence Visually opalescent with OP values above 9 OP values preferably above 12 Almost transparentor highly translucent in conditionshaded or notshaded (natural) Light transmittance greater than 45% at a wavelength of 560 nm or even across the spectral range from 560 nm to 700 nm for non-shaded or colored nanozirconianaturally; and greater than 35% at 560 nm or even over the entire spectral range from 560 nm to 700 nm for intentionally shaded nanozirconiadoped with coloring ions (to match inner or outer shadow patterns approximating teeth colors) Preferablylight transmittance greater than 50% at a wavelength of 560 nm or even across the spectral range from 560 nm to 700 nm for nanozirconia not shaded or colored naturally; and greater than 40% at 560 nm or even over the entire spectral range from 560 nm to 700 nm for nanozirconiaintentionally shadeddoped with coloring ions (to match inner or outer shadow patterns approximating the colors of the teeth). Total grain size range in fully sintered condition At least 95% of the grains by volume are 10 nm to 300 nm in size (or diameter), or 20 nm to 250 nm in size (diameter) All grains are 10 nm to 300 nm in size (or diameter) Grain size From 40 nm to 150 nm, Preferably
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    20/33
    Property Wide Range Preferred Range average measured according to the test method ASTM E112 (or EN 623-3)50 to 100 nm, and most preferably 50 to 80 nm. Residual density / porosity in fully sintered condition Pore size mostly greater than 30 nm where the density is greater than 99.5%. Most preferably, the porosity is less than 0.1% (density> 99.9% of theoretical density) Flexural strength Flexural strength ofISO 6872 of at least 800 MPa or higher Preferably> 1200 MPa flexural strength; and most preferably> 2 GPa of flexural strength Sinterable at temperatures <1200 ° Cwithout application ofexternal pressure (sintering without pressure) Sinterable at temperatures <1200 ° C usingconventional dental ovens or ovensdental microwaves Sinterable at temperatures <1150 ° C usingdental ovensconventional or dental microwave ovens Molded byCAD / CAM, EPD,LPIM, dental thermal pressing(such as glass ceramic ingots) similar to LPIM and gel casting using RP molds The preferred mode is machining of partially sintered voids formed by slip casting (limited use - for coarse nanoparticles only), centrifugal casting, drip casting, gel casting, injection molding, filter pressing and electrophoretic deposition (EPD)
    [0077] In order to further illustrate the advantageous properties listed in the table above, Figures 3A and 3B compare the light transmittance and the opalescence of the nanozirconia materials of the pre
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    21/33 feels an invention with commercial dental zirconia materials.
    In a preferred embodiment, the process shown schematically in Figure 4 will result in millable empty spaces (millable) green or pre-sintered (brown) that can be further processed in dental articles such as dental restorations (empty spaces, full contour FPDs ( fixed partial dentures), bridges, implant bridges, multi-unit structures, abutments, crowns, partial crowns, veneers, inlays, onlays, orthodontic retainers, space maintainers, tooth replacement devices, splints, dentures, abutments (posts), teeth , jackets, coatings, veneers, implants, cylinders, and connectors) using commercially available dental CAD / CAM systems. In alternative modalities, dental articles can be formed directly from suspension by EPD, gel casting in expanded molds formed by rapid prototyping (RP). In another alternative embodiment, the nanoparticles of the present invention can be provided as a raw material for injection molding. In the latter case, the expanded molds for low pressure injection molding (LPIM) can be formed by RP. RP is useful for forming molds that are enlarged to compensate for isotropic sintering shrinkage of the materials of the present invention when they are sintered from a green or pre-sintered state to full density.
    [0078] It is important to note that highly translucent tetragonal nanozirconia structures were produced from two types of nanozirconia suspensions covering the wide range of processing scenarios as shown in the spreadsheet in Figure 4. Nanozirconia suspensions (0% Y2O3) Pixelligent organic base (Pixeligent Technologies, Baltimore, MD) with ~ 14% by volume solids loading and 3Y-TZP suspension (3% in Y2O3 moles) MEL (MEL Chemicals, Flemington, NJ) aqueous base with solids from
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    22/33 ~ 5% by volume.
    EXAMPLES
    [0079] Non-limiting examples illustrating some of the modalities and features of the present invention are further elucidated in Figures 6 to 13. Commercially available nanozirconia suspensions have been received from several manufacturers. The most useful suspensions preferably comprise well-dispersed nanoparticles with an average primary particle size of <20 nm and preferably <15 nm. In some cases nanosuspensions comprising partially agglomerated and / or associated nanoparticles can also be used with average particle sizes up to 40 to 80 nm. The latter will require friction grinding to deglomerate and commune nanoparticles up to the required size range. The starting zirconia concentration is generally low, for example, 5% by volume, but concentrated suspensions are also available from some manufacturers (see Figure 13B). These concentrated suspensions may contain proprietary dispersants. The liquid medium of the suspension is preferably water, and it can also be organic solvents, for example, ethanol, methanol, toluene, dimethylformamide, etc. or mixtures thereof. The suspension was stabilized by adding dispersants and adjusting the pH. A dispersant used to stabilize nanosuspensions in the examples below was one of the following: Poly (ethyleneimine), 2- [2- (2-Methoxyethoxy) ethoxy] acetic acid, or 2- (2-Methoxyethoxy) acetic acid. The amount of dispersants by weight of solid zirconia was no more than 10% (for example, from 0.5% by weight to 10% by weight). The pH values of the suspension were in the range of 2 to 13. Centrifugation and / or friction grinding can be applied to remove and / or disrupt the agglomerated / aggregate portion of solids before or after stabilization of the suspensions. In some cases, binders can be used
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    23/33 added to the suspension in order to reinforce the casting strength. The suspensions were then concentrated by evaporating the solvents at an elevated temperature with or without a vacuum. After concentration, the suspension will be above 10% by volume, for example, preferably at least 14% by volume, preferably 16%, most preferably 18% by volume, and up to 50% by volume depending on requirements of training methods. After concentration, the viscosity (measured at 25 ° C) of the suspensions concentrated before casting will be well below 100 cP and in most cases below 30 cP, most preferably the viscosity will be at or below 15 cP once that this viscosity level produced better casting results. Friction grinding can also be used during or after the concentration process to essentially decompose agglomerates and aggregates and sometimes to reduce particle size.
    [0080] Concentrated zirconia suspensions with desired solids fillers were then used to melt green zirconia structures. Forming methods include: slip casting, gel casting, electrophoretic deposition, drip casting, filter pressing, injection molding, and centrifugal casting as well as other known applicable forming methods. After casting, the green structures were dried in an environment of controlled temperature, pressure, and humidity in order to ensure the formation of crack-free articles. Drying conditions are generally dictated by the dimensions of the articles: for example, thicker articles require longer drying time to prevent cracking. After drying, the green structures were at least 35%, preferably 45%, more preferably more than 50% of the theoretical density. The dry green structures were burned to remove organic species
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    24/33 including dispersants, binders, and any other additives. The peak neutralization temperature was not greater than 700 ° C, preferably from 500 ° C to 600 ° C. Optional pre-sintering can be carried out at temperatures up to 850 ° C. After neutralization, the articles, called brown structures, were then sintered at temperatures below 1200 ° C to reach full density. Sintering can be carried out in dental ovens, in traditional high-temperature ovens, or in hybrid microwave ovens. The density of the sintered articles was measured by the Archimedes method using water as the immersion medium. The relative density, calculated using a theoretical density value of 6.08 g / cm 3 , is generally> 99.5% in articles fully sintered in the present invention.
    [0081] The fully sintered samples were then crushed to 1.0 mm for measurement of optical properties. Transmittance and reflectance were measured by a Konica Minolta CM-3610d Spectrophotometer, according to the CIELAB color scale in reflectance and transmittance mode compared to the standard D65 illuminant. The opening diameter was 11 mm for measuring reflectance and 20 mm for measuring transmittance. The measurements were repeated five times for each sample and the values were weighted to obtain the final reading. The transmittance of green structures through a thickness of 1 mm was at least 50% at 560 nm, and was at least 45% for brown structures.
    [0082] The opalescence parameter was calculated as:
    [0083] PB = [(CLEA -ClEa T * R *) 2 + (CIEbT -ClEbR * *) 2] 1/2, whereas (* cleat -C Ea * R) is the difference between the transmission modes and reflectance in the red-green color coordinate, a * of the CIE L * a * b * color space; (C! Eb T * -ciEb R *) is the difference between the transmission and reflectance modes in the color coordinates
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    25/33 yellow-blue, b * from the CIE L * a * b * color space.
    [0084] Measurements of biaxial flexural strength were performed by an MTS Q Test machine on disc samples with a thickness of 1.2 ± 0.2 mm according to the ISO 6872-2008 standard. Sintered samples were also polished, thermally etched and studied by imaging under a scanning electron microscope Zeiss Sigma Field Emission (SEM). The average grain size was calculated by the interception method according to the ASTM E112-12 standard.
    Example 1
    [0085] 2 kg of 5% by volume aqueous suspension of yttria (3 mol%) of stabilized zirconia nanoparticulate was received from Mel Chemicals (Flemington, NJ). This suspension was de-agglomerated by centrifugation at 7000 rpm for 40 minutes. Then the suspension was stabilized by adding 2% dispersants by weight of solid zirconia. The pH of such a stabilized suspension was 2.5. This suspension was concentrated from 5% by volume to 18% by volume of solid load with an Ika RV10 vacuum evaporator at 40 ° C and 40 mbar for about 4 hours. Cylindrical PTFE molds from 18 mm to 32 mm in diameter and 10 mm in height were prepared, and the zirconia suspension was poured into the molds. 5 to 15 g of semi-slurry was applied to each mold depending on the desired final thickness. Then the suspended molds were placed inside an environmental chamber for curing and drying. During the first 72 ~ 120 hours, the humidity was above 85% and the temperature was around 25 ° C. The drying time was determined by the thickness of the samples. The thicker samples took a longer time to dry without cracking. Then the ambient humidity gradually decreased to about 20%, where the final water content in the green structures reached less than 4% by weight. The structures
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    26/33 green as formed were ~ 49% of theoretical density. The transmittance was 58% for a 2 mm thick green structure at 560 nm. The dry green structures were burned by heating at a speed of 0.5 ° C / min to 550 ° C and maintained for two hours. The brown structures, 1.8 mm thick, had a transmittance of 49% at 560 nm. The brown structures were then sintered in a dental oven (Programat P500, Ivoclar Vivadent AG.) At a ramp rate of 10 ° C / min to 1150 ° C, maintained for two hours, and then naturally cooled in air. After sintering, the disk samples were 12 to 23 mm in diameter and 1.5 mm thick, with a relative density of 99.98%. Probably due to contamination by Fe, Ni or Cr of the stainless steel equipment used in the manufacture of the starting nanozirconia suspensions, all the samples completely sintered in Example 1 to Example 6 appeared tinted, that is, notably brownish yellow in color. that resembles the natural color of the teeth.
    [0086] Then the samples were ground to a thickness of 1.0 mm for measurements of transmittance and reflectance. The transmittance of similar tinted samples was 37.7%, and the opalescence factor was 13.6. A SEM image of a polished and thermally etched cross section is shown in Figure 7, and the average grain size is 136 nm. The biaxial flexural strength is 2108 ± 386 MPa.
    [0087] In the following parallel experiments, all processing conditions remained identical, with the exception that the binder neutralization and / or sintering conditions were modified.
    [0088] For Example 1B, sintering was carried out at 1125 ° C for two hours.
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    [0089] In example 1C to 1F, a two-step sintering method was adapted, heating the samples to a higher temperature (for example, 1125 ° C, 1150 ° C) for a very short time (for example, 6 seconds), and then rapidly dropping to a lower temperature (for example, 1075 ° C, 1050 ° C) and holding for an extended period of time.
    [0090] In Example 1C, the sample was heated from room temperature to 1125 ° C at a speed of 10 ° C / min and maintained at 1125 ° C for 6 seconds; then it was cooled to 1075 ° C quickly and maintained at 1075 ° C for 20 hours. A SEM image of a polished and thermally etched cross section is shown in Figure 8, and the average grain size is 112 nm. The biaxial flexural strength is 1983 ± 356 MPa.
    [0091] In example 1D, the sample was heated from room temperature to 1150 ° C at a speed of 10 o C / min and maintained at 1150 ° C for 6 seconds; then it was cooled to 1075 ° C quickly and maintained at 1075 ° C for 20 hours. The biaxial flexural strength is 2087 ± 454 MPa.
    [0092] In example 1E, the sample was heated from room temperature to 1125 ° C at a speed of 10 ° C / min and maintained at 1125 ° C for 6 seconds; then it was cooled to 1075 ° C quickly and maintained at 1075 ° C for 15 hours.
    [0093] In example 1F, the sample was heated from room temperature to 1125 ° C at a speed of 10 ° C / min and maintained at 1125 ° C for 10 seconds; then it was cooled to 1075 ° C quickly and maintained at 1075 ° C for 20 hours.
    [0094] In another parallel experiment, the conditions for binder neutralization were changed. Example 1G was processed under all conditions identical to Example 1C, with the exception that the peak neutralization temperature was increased by 550 ° C
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    28/33 to 700 ° C.
    [0095] Results on measurements of density, biaxial flexural strength, grain size, light transmittance, and opalescence are summarized in Table 1 below.
    TABLE 1
    Ex. Dispersant Load ofSolids (% by volume) Sintering DensityRelative% Biaxial flexural strength (MPa) Average grain size (nm) Light Transmission @ 560 nm Color Opalescence Factor 1A 2% 18 1150 / 2h 99.98 2108 ± 386 136 38 brownish yellow,tooth-like hue 14 1B 2% 18 1125 / 2h 99.96 114 38 brownish yellow,tooth-like hue 14 1C 2% 18 1125 / 6s-1075 / 20h 99.95 1983 ± 356 112 40 brownish yellow,tooth-like hue 15 1D 2% 18 1150 / 6s-1075 / 20h 99.90 2087 ± 454 - 39 brownish yellow,tooth-like hue - 1 AND 2% 18 1125 / 6s-1075 / 15h 99.91 - - 39 brownish yellow,tooth-like hue 14 1F 2% 18 1125 / 10s-1075 / 20h 99.92 - - 38 brownish yellow,tooth-like hue 15 1G 2% 18 1125 / 6s-1075 / 20h 99.92 - - 39 brownish yellow,tooth-like hue 13 2A 2% 18 1100 / 4h 99.94 - 108 - brownish yellow,tooth-like hue - 2B 2% 18 1125 / 2h 99.94 - - 38 brownish yellow,tooth-like hue - 2C 2% 18 1100 / 3h 99.96 - - 39 brownish yellow,tooth-like hue 14 2D (2 + 3)% 18 1125 / 2h 99.90 - - - brownish yellow,tooth-like hue - 2E 4% 18 1125 / 2h 99.92 - 119 - brownish yellow,tooth-like hue - 3A 2% 14 1150 / 2h 99.92 - 131 37 brownish yellow,tooth-like hue - 3B 2% 14 1125 / 6s-1075 / 20h 99.91 - 107 39 brownish yellow,tooth-like hue - 4A 2% 18 1125C / 2h 99.86 - - - brownish yellow,tooth-like hue - 4B 2% 18 1125 / 6s-1075 / 20h 99.9291 - brownish yellow,tooth-like hue - 5 2% 18 1150 / 2h 99.50 - - - brownish yellow,tooth-like hue - 6 2% 18 1150 / 2h 99.90 - - - brownish yellow,tooth-like hue -
    Example 2
    [0096] The preparation and concentration steps of the suspension were
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    29/33 were identical to Example 1A. After concentration and before casting, an addition step, friction milling, was carried out using a Netzsch MiniCer friction mill. The concentrated suspension was ground with 200, 100, or 50 pm of yttrium-stabilized zirconia beads at a rotation speed of 3000 rpm. After friction grinding, the suspension was melted into PTFE molds, dried, and burned in the same procedures as in Example 1A.
    [0097] For Example 2A, the friction grinding time was one hour, and the brown structures were sintered at 1100 ° C for 4 hours.
    [0098] For Example 2B, the friction grinding time was 1.5 hours, and the brown structures were sintered at 1125 ° C for two hours.
    [0099] For Example 2C, the friction grinding time was 1.5 hours, and the brown structures were sintered at 1100 ° C for 3 hours.
    [00100] For Example 2D, after original friction milling for 1.5 hours at 3000 rpm in the friction mill, an additional 3% by weight (according to the zirconia weight) of additives was added to the suspension. The friction grinding continued for another hour. The suspension was melted into molds, dried, and burned in the same procedures as in Example 1A. Then the sample was sintered at 1125 ° C for two hours.
    [00101] For Example 2E, the suspension and preparation steps were identical to Example 1A with the exception that 4% by weight of dispersant was used. After concentration, friction grinding was carried out for 3 hours. The samples were sintered at 1125 ° C for two hours.
    [00102] Density, optical properties, and grain size were measured and reported in Table 1. SEM image of the example
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    30/33
    2A is shown in Figure 9, where a pore of ~ 35 nm in diameter was observed. All samples are visually opalescent.
    Example 3
    [00103] In the stabilization step, a dispersant other than 2% by weight was used compared to Example 1A, and the suspension was concentrated to 14% by volume. After concentration, the suspension was melted into the molds. Drying and firing were carried out in procedures identical to Example 1A.
    [00104] For Example 3A, the sample was heated to 1150 ° C at 10 ° C / min and held for two hours.
    [00105] For Example 3B, the sample was heated to 1125 ° C with a speed of 10 ° C / min and maintained at 1125 ° C for 10 seconds; then it was cooled to 1075 ° C quickly and maintained at 1075 ° C for 20 hours.
    [00106] The density, optical properties, and grain size were measured and reported in Table 1. All samples were visually opalescent.
    Example 4
    [00107] The stabilization, concentration, and processing conditions of the suspension are identical to Example 1A with the exception that the brown structures were sintered in a high temperature microwave assisted oven, MRF 16/22, Carbolite, Hope Valley, UK United.
    [00108] In Example 4A, the sample was heated at 10 ° C / min to 1125 ° C in the IR sensor controlled mode, with microwave on after 700 ° C in automatic mode. Then the sample remained at 1125 ° C under microwave at 500 W for two hours. The sample was cooled naturally.
    [00109] In Example 4B, the sample was heated at 10 ° C / min to 1125 ° C in the IR sensor controlled mode for 6 seconds, and in
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    31/33 was then maintained at 1075 ° C for 20 h. During heating, the microwave started at 700 ° C in automatic mode, and during the stay the microwave was manually adjusted to 200 W.
    [00110] The density and grain size were measured and reported in Table 1. Figure 10 shows the microstructure of Example 4B with average grain size of 91 nm and density of 99.92%. All the sintered samples referred to are visually opalescent.
    Example 5
    [00111] 500 g of 5% by volume aqueous suspension of 3 mol% yttrium-stabilized zirconia nanoparticles was received from Mel Chemicals (Flemington, NJ). This suspension was stabilized by adding 3% by weight of dispersants by weight of solid zirconia. The stabilized suspension was concentrated from 5% by volume to 18% by volume in a glass beaker by heating while stirring at 50 ° C for 14 hours in a water bath with a hot plate. Slip casting was performed using plaster molds, prepared by casting cylinders 32 mm in diameter, and 30 mm high with plaster of the type USG No. 1 Pottery Plaster. The cylinders were wrapped with plastic paper to close the semi-fluid pastes before consolidation. 5 to 15 g of concentrated semi-slurry was poured into each mold depending on the desired final thickness. After the slurry had been consolidated, the plastic paper was removed, and the consolidated parts were removed from the plaster and placed in a drying box to cure and drying under controlled humidity (identical to Example 1A). After drying, the green structures were burned at a rate of 0.5 o C / min to 700 ° C and maintained for two hours. The brown structures were sintered in a dental oven (Programat P500, Ivoclar Vivadent AG.) By heating at a rate of 10 ° C / min to 1150 ° C and maintained for two hours.
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    [00112] The relative density of articles formed in this way has been measured to be 99.50%. All the formed articles referred to were visually opalescent.
    Example 6
    [00113] The suspension was stabilized, concentrated and de-agglomerated in the identical steps as illustrated in Example 1A. 40 ml of suspension was then transferred to a PTFE centrifuge vessel and centrifuged at 11000 rpm for 40 min by Legend XT Centrifuge, ThermoScientific. After that, the supernatant was carefully removed by pipetting. The dense part of the bottom remained in the PTFE pot and was dried for 15 days. After the part had dried completely, it was removed from the mold and burned at 700 ° C for two hours. The brown structure formed in this way was ground into a veneer realistically molded with a magnification factor of 1.25 and sintered. Sintering was carried out in a Programat P500 dental oven at 1150 ° C for two hours, and the density was measured to be 99.90%. The veneer formed in this way was polished to a glossy finish with a thickness between 0.3 to 1.5 mm. It appears opalescent as shown in Figure 6.
    Example 7
    [00114] A suspension of nanozirconia based on organic solvent (0% Y2O3) was received from Pixelligent Technologies (Baltimore, MD). The suspension concentration as received was 14.0% by volume with an average particle size of 5 to 8 nm in a toluene solution. This suspension was concentrated by slowly evaporating the solvent under ambient conditions in a PTFE tube. After the part had dried completely, it was then removed from the tube and subjected to neutralization at 550 ° C for two hours. Both green and brown structures were transparent. It was made
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    33/33 sintering at temperatures from 900 ° C to 1100 ° C for one hour. The phase and grain sizes were measured and calculated by X-ray diffraction with low incidence and SEM, and the results are listed in Table 2. Some opalescence can only be observed in samples sintered at 1000 ° C and 1050 ° C. There is no hue observed for any of the sintered structures; they appeared basically colorless. The highest density for the sintered structures was 98.3%, and all samples showed severe cracking after heat treatment. The results on visual appearance, density, grain size and phase composition are listed in Table 2 below.
    TABLE 2
    Sintering Temp ° C 900 950 1000 1050 1100 Aspect (seeFigure 12) Transparent Window Transparent Window Translucent with someopalescence Translucent with someopalescence Opaque Density (%) at 98.3 ± 0.2 97.8 ± 0.2 95.5 ± 0.1 AT Size ofgrains estimated from SEM (nm) at at 35 40 90 Size ofgrains from XRD (nm) 7 13 18 22 18 Phases Tetragonal phase Monoclimate phasenica> 90
    [00115] Although preferential modalities have been represented and described in detail here, in this patent application, it will be evident to those skilled in the relevant art that various modifications, additions, substitutions, and the like can be made without departing from the spirit of the invention and these they are therefore considered to be within the scope of the invention as defined in the claims that follow.
    权利要求:
    Claims (24)
    [1]
    1. Dental zirconia ceramic, characterized by the fact that it comprises:
    predominantly tetragonal zirconia with less than 15% of combined monoclinic and cubic phases;
    at least 95% of all grains per volume within the range 10 nm to 300 nm;
    a density of at least 99.5% of the theoretical density; and showing opalescence.
    [2]
    2. Dental zirconia ceramic, according to claim 1, characterized by the fact that it comprises an average grain size from 40 nm to 150 nm.
    [3]
    3. Dental zirconia ceramic, according to claim 1, characterized by the fact that at least 95% of all grains are within the range of 20 nm to 250 nm.
    [4]
    4. Dental zirconia ceramic, according to claim 1, characterized by the fact that all grains are within the range of 10 nm to 300 nm.
    [5]
    5. Dental zirconia ceramic, according to claim 1, characterized by the fact that the opalescence is at least 9 and the opalescence is measured on a 1 mm thick sample using the formula
    OP = [(CIEa T * -CIEa R *) 2 + (CIEb T * -CIEb R *) 2 ] 1/2 , where (ciEa T * -ciEa R *) is the difference between the transmission and reflectance in the coordinates of the red-green colors a * of the CIE L * a * b * color space; and where (ciEb T * -ciEb R *) is the difference between the transmission and reflectance modes in the yellow-blue b * color coordinate of the CIE L * a * b * color space.
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    2/5
    [6]
    6. Dental zirconia ceramic, according to claim 1, characterized by the fact that it comprises a visible light transmittance to a thickness of one millimeter of more than 45% at a wavelength in the range of 560 nm to 700 nm.
    [7]
    7. Dental zirconia ceramic according to claim 1, characterized by the fact that it is a shaded zirconia ceramic and comprises a visible light transmittance to a thickness of one millimeter of more than 35% over a wavelength in the range from 560 nm to 700 nm.
    [8]
    8. Zirconia dental ceramics, according to claim 1, characterized by the fact that it comprises a flexural strength of at least 800 MPa.
    [9]
    9. Dental zirconia ceramic, according to claim 1, characterized by the fact that it comprises YTZP (yttria-stabilized tetragonal zirconia polycrystalline) with 0 to 3 mol% of Y2O3.
    [10]
    10. Dental zirconia ceramic, according to claim 1, characterized by the fact that it comprises less than 0.5% porosity, in which most pores are at least 25 nm in diameter.
    [11]
    11. Dental zirconia ceramic, according to claim 1, characterized by the fact that zirconia comprises a stabilizing additive selected from Y, Ce, Mg, or mixtures thereof.
    [12]
    12. Dental zirconia ceramic, according to any one of claims 1 to 11, characterized by the fact that it comprises:
    at least 95% of all grains per volume within the range of 10 nm to 300 nm with an average grain size of 40 nm to 150 nm;
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    3/5 a transmittance of visible light to a thickness of one millimeter of more than 45% at a wavelength in the range of 560 nm to 700 nm;
    a flexural strength equal to or greater than 800 MPa measured according to the international standard ISO 6872: 2008 for dental ceramics;
    a density greater than or equal to 99.5% of the theoretical density; and most pores larger than 25 nm.
    [13]
    13. Dental zirconia ceramics according to any one of claims 1 to 12, characterized by the fact that it is manufactured by modeling a green, brown or pre-sintered zirconia material and sintering it to full density by pressure-free sintering without applying external pressure at temperatures below 1200 ° C.
    [14]
    14. Dental article, characterized by the fact that it comprises zirconia dental ceramics as defined in any one of claims 1 to 13.
    [15]
    15. Method for manufacturing an opalescent zirconia dental article, characterized by the fact that it comprises:
    providing a well-dispersed suspension of zirconia nanoparticles having an average particle size of less than 20 nm;
    model the suspension in a dental article format or an empty space to produce a green wet zirconia structure;
    drying the green wet structure in a controlled humidity atmosphere to produce a green zirconia structure;
    heat the green zirconia structure to provide a brown zirconia structure, where the green zirconia structure
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    4/5 nia is shaped before heating, or the brown zirconia structure is shaped after heating;
    sintering the brown zirconia structure at a temperature below or equal to 1200 ° C to provide a sintered opalescent zirconia structure;
    where a grain size resulting from the sintered dental article is between 10 and 300 nm and an average grain size is between 40 nm and 150 nm and / or where most pores are larger than 25 nm at a density of at least 99.5% of the theoretical density, and in which the sintered dental article comprises predominantly tetragonal zirconia with less than 15% of combined monoclinic and cubic phases.
    [16]
    16. Method according to claim 15, characterized by the fact that the heating step comprises heating the green zirconia structure to a temperature in the range from 500 to 700 ° C to remove any organic residues to form a structure zirconia brown.
    [17]
    17. Method according to claim 15, characterized by the fact that it additionally comprises pre-sintering the brown structure at a temperature up to 850 ° C before sintering, in which the pre-sintering step and the heating step can be combined in one step.
    [18]
    18. Method according to claim 15, characterized in that the step of forming the suspension in a format comprises a uniform, isotropically enlarged format.
    [19]
    19. Method, according to claim 15, characterized by the fact that the dry green structure or brown structure is shaped by CAD / CAM, LPIM or dental thermal pressing.
    [20]
    20. Method according to claim 15, characterized by the fact that the well-dispersed suspension of nanoparticles of
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    5/5 zirconia comprises a percentage by volume of particulate solids in the range of 10 to 50 vol%.
    [21]
    21. Method according to claim 15, characterized in that the well-dispersed suspension additionally comprises a dispersant in an amount of not more than 10% by weight of total solids in the suspension.
    [22]
    22. Method according to claim 21, characterized in that the dispersant comprises poly (ethyleneimine), 2- [2- (2-methoxyethoxy) ethoxy] acetic acid, or 2- (2-methoxyethoxy) acetic acid.
    [23]
    23. Method according to claim 15, characterized in that the well-dispersed suspension is additionally de-agglomerated by friction grinding.
    [24]
    24. Method according to claim 23, characterized in that the suspension is further refined by centrifugation instead of, before, or after friction grinding.
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    同族专利:
    公开号 | 公开日
    BR112015032559A2|2017-07-25|
    CA2913112C|2020-06-16|
    US20200222287A1|2020-07-16|
    WO2014209626A1|2014-12-31|
    KR20160023766A|2016-03-03|
    CN105338948B|2019-02-01|
    CN105338948A|2016-02-17|
    US20160095798A1|2016-04-07|
    JP2016523286A|2016-08-08|
    EP3013306B1|2020-07-22|
    US20180133112A1|2018-05-17|
    CA2913112A1|2014-12-31|
    BR112015032559A8|2020-01-07|
    JP6679687B2|2020-04-15|
    KR102215498B1|2021-02-15|
    US10004668B2|2018-06-26|
    JP6416247B2|2018-10-31|
    ES2815073T3|2021-03-29|
    US10610460B2|2020-04-07|
    JP2019005627A|2019-01-17|
    EP3013306A1|2016-05-04|
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    法律状态:
    2018-01-23| B07D| Technical examination (opinion) related to article 229 of industrial property law [chapter 7.4 patent gazette]|
    2018-05-15| B07B| Technical examination (opinion): publication cancelled [chapter 7.2 patent gazette]|
    2019-07-30| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|
    2020-04-28| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|
    2020-06-16| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 12/06/2014, OBSERVADAS AS CONDICOES LEGAIS. |
    优先权:
    申请号 | 申请日 | 专利标题
    US201361840055P| true| 2013-06-27|2013-06-27|
    US61/840,055|2013-06-27|
    PCT/US2014/042140|WO2014209626A1|2013-06-27|2014-06-12|Nanocrystalline zirconia and methods of processing thereof|
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