SHOFU INC.

To provide a zirconia mill blank for dental cutting and machining that can significantly change the translucency of the sintered body while maintaining high strength by changing the sintering temperature. To provide a zirconia mill blank for dental cutting and machining, containing a stabilizer in an amount of 5.8 mol % or more and 7.0 mol % or less in terms of oxide, and substantially no alumina, wherein the zirconia mill blank for dental cutting and machining has a portion satisfying a condition that a crystal grain size of sintered body in the case of producing by sintering at 1550° C. for 1 hour is 2.0 times or more of a crystal grain size of sintered body in the case of producing by sintering at 1450° C. for 1 hour.

To manufacture a dental zirconia pre-sintered body for cutting and machining with little warpage without limiting the powder composition to be stacked to specific coloring materials or stabilizers, and with no distortion after perfect sintering. In the step of forming a second or more layers, a zirconia powder for layering used in a green compact constituting each layer is different from a zirconia powder for layering used in a green compact constituting adjacent layer in relative density to the perfect sintered body in the green compact pressed at a press pressure of 4.78 kN/cm 2 , and each press pressure of the powder compacting in forming the green compact that constitutes each layer is adjusted so that the difference in relative density between the green compacts constituting respective layers is 2 or less, and in the step of pre-sintering, the multilayer zirconia green compact is pre-sintered at a temperature at which the processing coefficients of respective layers after pre-sintering are substantially equal.

[Problem] A technique for improving translucency in order to prepare a zirconia sintered body having high translucency without using special equipment, has been required. [Solution] To provide A sintering method for a dental zirconia calcined body containing 5.5 mol % to 7.0 mol % of a stabilizer, wherein the method satisfies the following (a) to (c). (a) an average rate of temperature increase in the section from room temperature to 1300° C. is 9° C./min or more. (b) an average rate of temperature increase in the section from 1300° C. to 1400° C. is 0.6° C./min or more and 3° C./min or less. (c) an average rate of temperature increase in the section from 1400° C. to the maximum temperature of the sintering process is 0.5° C./min or more and 2.5° C./min or less.

To provide a ceramic mill blank for dental cutting and machining in which cracks or chips are not caused on the outer edge of the ceramic mill blank even if attaching to and detaching from a dental milling machine are repeated and it is possible to machine the vicinity of the outer edge of the ceramic mill blank. To provide a ceramic mill blank for dental cutting and machining, wherein, the ceramic mill blank for dental cutting and machining comprises a ceramic portion to be cut and machined and one or more seal members, the ceramic portion consists of a ceramic material which is not finally sintered, the ceramic portion has an outer peripheral surface which is engageable with a holding tool, the one or more seal members are provided on the outer peripheral surface of the ceramic portion, and a length of the one or more seal members is 50% or more of a length in a circumferential direction of the outer peripheral surface provided with the one or more seal members.

To provide a zirconia perfect sintered body which has a chroma of an excellent color tone and excellent translucency as compared with a zirconia mill blank for dental cutting and machining prepared from a zirconia raw material powder containing various stabilizing materials while maintaining high strength, and does not cause deformation. The zirconia mill blank of the present invention is a semi-fired zirconia mill blank for dental cutting and machining containing a semi-fired body of a ceramic particle, the zirconia mill blank for dental cutting and machining contains zirconium oxide, a stabilizing material consisting of an oxide, and a water-soluble compound salt which contains at least one element selected from calcium, magnesium and a rare earth element and is not an oxide, the content of the stabilizing material in terms of the oxide in the semi-fired body of the ceramic particle is within a range of 2 to 7 mol %, and the content of the water-soluble compound salt in the zirconia mill blank for dental cutting and machining is within a range of 0.1 to 3.5 mol %.

To provide a zirconia perfect sintered body which has a chroma of an excellent color tone and excellent translucency as compared with a zirconia mill blank for dental cutting and machining prepared from a zirconia raw material powder containing various stabilizing materials while maintaining high strength, and does not cause deformation. The zirconia mill blank of the present invention is a semi-fired zirconia mill blank for dental cutting and machining containing a semi-fired body of a ceramic particle, the zirconia mill blank for dental cutting and machining contains zirconium oxide, a stabilizing material consisting of an oxide, and a water-soluble compound salt which contains at least one element selected from calcium, magnesium and a rare earth element and is not an oxide, the content of the stabilizing material in terms of the oxide in the semi-fired body of the ceramic particle is within a range of 2 to 7 mol %, and the content of the water-soluble compound salt in the zirconia mill blank for dental cutting and machining is within a range of 0.1 to 3.5 mol %.

To provide a zirconia perfect sintered body which has a chroma of an excellent color tone and excellent translucency as compared with a zirconia mill blank for dental cutting and machining prepared from a zirconia raw material powder containing various stabilizing materials while maintaining high strength, and does not cause deformation. The zirconia mill blank of the present invention is a semi-fired zirconia mill blank for dental cutting and machining containing a semi-fired body of a ceramic particle, the zirconia mill blank for dental cutting and machining contains zirconium oxide, a stabilizing material consisting of an oxide, and a water-soluble compound salt which contains at least one element selected from calcium, magnesium and a rare earth element and is not an oxide, the content of the stabilizing material in terms of the oxide in the semi-fired body of the ceramic particle is within a range of 2 to 7 mol %, and the content of the water-soluble compound salt in the zirconia mill blank for dental cutting and machining is within a range of 0.1 to 3.5 mol %.

To provide a preparing method of a zirconia mill blank for dental cutting and machining having any one or more of translucency gradation, color gradation and strength gradation after perfect sintering by impregnating a zirconia calcined body with a plurality of impregnating solutions, which can suppress deterioration of the fitting property of a dental prosthesis device prepared from the zirconia mill blank for dental cutting and machining and a zirconia mill blank for dental cutting and machining having any one or more of translucency gradation, color gradation and strength gradation after perfect sintering and suppressing deterioration of the fitting property of a dental prosthesis device prepared from the zirconia mill blank for dental cutting and machining. To porovide a zirconia mill blank for dental cutting and machining of the present invention is a preparing method of a zirconia mill blank for dental cutting and machining having any one or more of translucency gradation, color gradation and strength gradation after perfect sintering, comprising a step of impregnating a zirconia calcined body with at least two types of impregnating solutions, wherein at least one of the impregnating liquids contains a zirconium component, and in a case in which the total of metal ion concentrations (mass %) contained in each impregnating liquid is defined as C total , the difference ΔC total which is a difference between C total of each impregnating liquid is 5.0 or less.

To provide a zirconia mill blank for dental cutting and machining which has excellent machinability in a thin workpiece such as an inlay, an onlay and a veneer, and may impart high strength and high translucency to a zirconia perfect sintered body without a special sintering such as HIP treatment, and a preparing method thereof. The zirconia mill blank for dental cutting and machining has a porosity within a range of 15 to 30%.

To provide a zirconia mill blank for dental cutting and machining which has excellent machinability in a thin workpiece such as an inlay, an onlay and a veneer, and may impart high strength and high translucency to a zirconia perfect sintered body without a special sintering such as HIP treatment, and a preparing method thereof. The zirconia mill blank for dental cutting and machining has a porosity within a range of 15 to 30%.