Phosphate-based dental investment material

Abstract

To provide a phosphate-based dental investment material which can used for metal and press ceramic and especially can impart the lubricity to the surface of a press ceramic, and a phosphate-based dental investment material which can be subjected to a flash heating for press ceramic, can obtain sufficient the hardening expansion, and can easily remove the investment material after press molding. A phosphate-based dental investment material of the present disclosure comprising a powder material and a liquid material, wherein the powder material contains (a) magnesium oxide: 5 to 20 wt. %; (b) ammonium dihydrogenphosphate: 8 to 25 wt. % and the liquid material contains (c) aqueous solution including a cation-treated colloidal silica.

Claims

1. A phosphate-based dental investment material comprising a powder material and a liquid material, wherein the powder material contains (a) magnesium oxide: 5 to 20 wt. %; (b) ammonium dihydrogenphosphate: 8 to 25 wt. % and the liquid material contains (c) aqueous solution including a cation-treated colloidal silica, wherein the cation-treated colloidal silica is colloidal silica surface-treated with a cationic silane coupling material or a cationic metal element.

2. The phosphate-based dental investment material according to claim 1, wherein the content of alkali metals (in terms of oxide) in the (c) aqueous solution including cation-treated colloidal silica is in a range of 0.001 to 0.30 wt. %.

3. The phosphate-based dental investment material according to claim 1, wherein the pH of the (c) aqueous solution including cation-treated colloidal silica is in a range of 8.0 to 10.0.

4. A phosphate-based dental investment material comprising a powder material and a liquid material, wherein the powder material contains (a) magnesium oxide: 5 to 20 wt.%; (b) ammonium dihydrogenphosphate: 8 to 25 wt.% and the liquid material contains (c) aqueous solution including a cation-treated colloidal silica, wherein the cation-treatment is alumina compound treatment.

5. The phosphate-based dental investment material according to claim 2, wherein the pH of the (c) aqueous solution including cation-treated colloidal silica is in a range of 8.0 to 10.0.

6. A phosphate-based dental investment material comprising a powder material and a liquid material, wherein the powder material contains (a) magnesium oxide: 5 to 20 wt.%; (b) ammonium dihydrogenphosphate: 8 to 25 wt.% and the liquid material contains (c) aqueous solution including a cation-treated colloidal silica, wherein the content of alkali metals (in terms of oxide) in the (c) aqueous solution including cation-treated colloidal silica is in a range of 0.001 to 0.30 wt.%, and wherein the cation-treatment is alumina compound treatment.

7. A phosphate-based dental investment material comprising a powder material and a liquid material, wherein the powder material contains (a) magnesium oxide: 5 to 50 wt.%; (b) ammonium dihydrogenphosphate: 8 to 25 wt.% and the liquid material contains (c) aqueous solution including a cation-treated colloidal silica, wherein the pH of the (c) aqueous solution including cation-treated colloidal silica is in a range of 8.0 to 10.0, and wherein the cation-treatment is alumina compound treatment.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(1) A phosphate-based dental investment material according to the present disclosure will be described below. However, the present disclosure is not limited to following description.

(2) A phosphate-based dental investment material of the present disclosure consists of a powder material and a liquid material.

(3) The powder material contains (a) magnesium oxide and (b) ammonium dihydrogen phosphate.

(4) The type of the (a) magnesium oxide contained in the powder material is not particularly limited, but it is preferable that the purity of the (a) magnesium oxide is high and it is preferable that the (a) magnesium oxide is finely pulverized.

(5) An average particle diameter of the (a) magnesium oxide is not particularly limited, but the average particle diameter is preferably within a range of 15 to 40 m, more preferably within a range of 20 to 30 m. In the particle size distribution of the magnesium oxide, it is preferable that a ratio of particle having 100 m or more of a particle diameter is 1% or less, and it is more preferable that no particles having 100 m or more of a particle diameter are contained. Further, a combination of a plurality of the (a) magnesium oxides which have different average particle diameters can be used. In the case of using a combination of a plurality of the (a) magnesium oxides which have different average particle diameters, it is preferable that an average particle diameter of the (a) magnesium oxides after combination is within a range of 15 to 40 m.

(6) In order to exhibit the effect of the present disclosure in the phosphate-based dental investment material of the present disclosure, a compounded amount of the magnesium oxide must be within a range of 5 to 20 wt. % based on the powder material of the phosphate-based dental investment material. When the compounded amount of the magnesium oxide is less than 5 wt. %, because the sufficient strength of mold is not provided, it may be insufficient for mold material. When the compounded amount of the magnesium oxide is more than 20 wt. %, because the compounded amount of an aggregate becomes less, enough thermal expansion may be not provided.

(7) The (b) ammonium dihydrogen phosphate contained in the powder material constituting the phosphate-based dental investment material of the present disclosure is not particularly limited as long as it is soluble, and any ammonium dihydrogen phosphate can be used without any problem even if having any average particle diameter and any shape.

(8) However, in order to act as a binding material in an investment material, it is preferable that the maximum particle diameter of the ammonium dihydrogen phosphate is small. For maintaining the lubricative property of the surface of the molded body which is press-molded, it is preferable that no particle having a particle diameter of 60 m or more are contained. Further, a ratio of particles having a particle diameter of 25 m or less in the particles having a particle diameter of 60 m or more is preferably within a range of 10 to 45%, more preferably within a range of 20 to 35%.

(9) In order to exhibit the effect of the present disclosure in the phosphate-based dental investment material of the present disclosure, a compounded amount of the ammonium dihydrogen phosphate must be within a range of 8 to 25 wt. % based on the powder material of the phosphate-based dental investment material. When the compounded amount of the ammonium dihydrogen phosphate is less than 8 wt. %, because the sufficient strength of the cast mold is not provided, it may be insufficient for a mold material. When the compounded amount of the ammonium dihydrogen phosphate is more than 25 wt. %, a problem such that the surface property of a casting body or a pressed body becomes rough may be caused.

(10) With respect to a compounding ratio of the (a) magnesium oxide and the (b) ammonium dihydrogenphosphate which are contained in the powder material constituting the phosphate-based dental investment material of the present disclosure, the weight ratio of (a)/(b) is preferably within a range of 0.3 to 1.0 and is more preferably within a range of 0.4 to 0.8.

(11) The powder material constituting the phosphate-based dental investment material of the present disclosure may include an aggregate. Any refractory materials used in a dental casting investment material can be used as an aggregate without any limitation. Specific examples of an aggregate include quartz, cristobalite, fused quartz, alumina, zirconia, zirconium silicate, calcia and yttoria. Among them, zirconia, zirconium silicate, quartz and cristobalite are especially preferable. In order to adjust the fluidity of the investment material, a combination of a plurality of the aggregates which have average particle diameters within a range of 10 to 300 m can be used.

(12) In order to exhibit the effect of the present disclosure in the phosphate-based dental investment material of the present disclosure, a compounded amount of an aggregate is not particularly limited. However, in the case of using for a press ceramic, the compounded amount of cristobalite is desirably small, preferably within a range of 15 to 45 wt. % and more preferably within a range of 25 to 35 wt. %. On the other hand, the compounded amount of zirconia is preferably within a range of 5 to 10 wt. % and the compounded amount of zirconium silicate is preferably within a range of 5 to 15 wt. %.

(13) Next, the (c) aqueous solution including a cation-treated colloidal silica contained in the liquid material constituting the phosphate-based dental investment material of the present disclosure is described. In order to exhibit the effect of the present disclosure, it is essential that the surface of the colloidal silica is cation-treated. The methods of cation treatment are roughly divided into two kinds of methods including a treatment method using a cationic silane coupling material and a treatment method using a cationic metal element. A water-soluble metal salt may be included in addition to the colloidal silica. Specific examples include sodium chloride.

(14) The preparation methods of a colloidal silica are roughly divided into two methods. That is, two methods including a water glass method and an alkoxide method have been used mainly.

(15) In the water glass method, a sodium silicate is subjected to an ion exchange to prepare an active silicic acid, and the pH value is adjusted with NaOH under heating.

(16) The alkoxide method, otherwise known as the Stber method, comprises subjecting an alkyl silicate (tetraalkoxysilane) to hydrolyzation and condensation in the presence of a basic catalyst to grow particles, thereby producing silica particles. This method enables the preparation of colloidal particles having particle sizes ranging from nano- to microscale. For example, a colloidal silica having a minor axis diameter of 10 to 200 nm and a major-axis/minor-axis ratio of 1.4 to 2.2 may be prepared by dropping a methyl silicate (tetramethoxysilane) or a mixture of methyl silicate and methanol dropwise to a mixed solvent comprising water, methanol and ammonia, or to a mixed solvent comprising ammonia and ammonium salt under stirring for 10 to 40 minutes so as to allow the methyl silicate to react with water.

(17) When a cationic colloidal silica is prepared from a colloidal silica by using a silane coupling material, an aqueous solution including a colloidal silica is prepared in advance by the water glass method or the alkoxide method and then the colloidal silica is surface-treated with a silane coupling material. In addition, a commercially available aqueous solution including a colloidal silica may be used without any problem. In this case, a solid content concentration of an aqueous solution including a colloidal silica suitable for the present disclosure preferably is preferably within a range of 15 to 40 wt. %, more preferably within a range of 20 to 30 wt. %. Further, the primary particle diameter of this colloidal silica is not particularly limited, but is preferably within a range of 5 to 30 nm, and more preferably within a range of 8 to 20 nm.

(18) For a method for preparing an aqueous solution including a cationic colloidal silica by using a silane coupling material, there is a method to treat a colloidal silica by adding the treated amount of a silane coupling material to a colloidal silica aqueous solution and stirring. In addition, for example, a desired treatment liquid can be prepared by heating to 50 to 80 C. and stirring for 1 to 2 hours. It is preferable that the weight ratio of a colloidal silica aqueous solution and a silane coupling material is within a range of 50:1 to 5:1.

(19) Specific examples of the silane coupling material include N-(-aminoethyl)--aminopropyl methyldimethoxysilane, N-(-aminoethyl)--aminopropyl trimethoxysilane, N-(-aminoethyl)--aminopropyl triethoxysilane, -aminopropyltriethoxysilane, -aminopropyltrimethoxysilane, -triethoxysilyl-N-(, -dimethyl-butylidene) propylamine, N-phenyl--aminopropyltrimethoxysilane, hydrochloride of N-(vinylbenzyl)--aminoethyl--aminopropyl triethoxysilane and octadecyl dimethyl(-trimethoxysilylpropyl)ammonium chloride.

(20) Among them, N-(-aminoethyl)--aminopropyl trimethoxysilane, N-(-aminoethyl)--aminopropyl triethoxysilane, -aminopropyltriethoxysilane, -aminopropyltriethoxysilane and -aminopropyltrimethoxysilane are preferably used because of good reactivity to colloidal silica.

(21) These silane coupling materials can be used singly or in combinations of a plurality thereof.

(22) It is preferable that the pH value is adjusted to 8-10 by adding an alkali metal compound after a silane coupling treatment.

(23) Sodium hydroxide and potassium hydroxide are suitably used as an alkali metal compound.

(24) The other cation treatment method of a colloidal silica is a method for treating the surface with a metallic element. In this method, a metal compound is mixed in advance during a preparation of colloidal silica by the water glass method, an active silicic acid is prepared by an ion change of a sodium silicate and the pH value is adjusted by adding NaOH under heating. Specific examples of the metal compound include an alumina compound, a titanium compound, a zirconia compound or the like and a colloidal silica having a surface coated with these metal compounds can be used. The coating method is not particularly limited and a mixing reaction method in an aqueous solution can be used. An alumina compound treatment is particularly preferable.

(25) Specifically, sodium aluminate, sodium titanate, sodium zirconate or the like is added to a colloidal silica aqueous solution, and then heated and stirred to prepare a cation-treated colloidal silica.

(26) Sodium hydroxide and potassium hydroxide are suitably used as an alkali metal compound. In addition, the pH value is adjusted to 8-10 by adding an alkali metal compound.

(27) In this case, a solid content concentration of a cationic colloidal silica treated with a metal element is preferably within a range of 15 to 40 wt. %, more preferably within a range of 20 to 30 wt. %. Further, the primary particle diameter of this colloidal silica is not particularly limited, but is preferably within a range of 5 to 30 nm, and more preferably within a range of 8 to 20 nm.

(28) It is preferable that the (c) aqueous solution including a cation-treated colloidal silica contains an alkali metal, it is more preferable that the content of alkali metals (in terms of oxide) is 0.30 wt. % or less. Further, it is more preferable that the content of alkali metals (in terms of oxide) is 0.001 wt. % or more.

(29) When the content of alkali metals (in terms of oxide) is less than 0.001 wt. %, a problem of extreme elongation of the curing time of an investment material may occur. Further, when the content of alkali metals (in terms of oxide) is more than 0.30 wt. %, a problem of the surface roughness of a pressed-molded body may occur.

(30) Further, it is preferable that the pH value of the (c) aqueous solution including a cation-treated colloidal silica is within a range of 8.0 to 10.0. When the pH value is less than 8.0, a problem of extreme elongation of the curing time of an investment material may occur. When the pH value is more than 10.0, a problem of shortening of the curing time of an investment material may occur.

(31) With respect to a kneading ratio of the powder material and the liquid material in the phosphate-based dental investment material of the present disclosure, it is preferable that 17 to 25 ml, more preferably 18 to 22 ml of the liquid material, is kneaded with 100 g of the powder material.

(32) Hereinafter, the present disclosure is described by way of Examples in more detail, and specifically, but the present disclosure is not limited to these Examples.

Examples

(33) Hereinafter, the present disclosure is described by way of Examples in more detail, and specifically, but the present disclosure is not limited to these Examples. In the Examples, Microtrac HRA type (manufactured by Nikkiso Co., Ltd.) was used for measuring the particle size, and JIS standard sieve was used for sieving ammonium dihydrogenphosphate.

(34) [Powder Material]

(35) (Preparation of Magnesium Oxide Material)

(36) Magnesium oxide raw material was crushed and classified to prepare a magnesium oxide material in which the the average particle diameter is 25 m and the ratio of the particles having the particle diameter of 100 m or more is 1% or less.

(37) (Preparation of Ammonium Dihydrogenphosphate Material)

(38) Ammonium dihydrogenphosphate was crushed and adjusted so that the particles have diameters which can pass through a 250-mesh screen (60 m) and the ratio of particles which can pass through a 500-mesh screen (25 m) is 30 wt. % to prepare ammonium dihydrogenphosphate material.

(39) (Aggregate)

(40) Cristobalite (200-mesh screen (77 m) through), quartz (200-mesh screen (77 m) through), zirconium silicate (200-mesh screen (77 m) through), and zirconia (200-mesh screen (77 m) through) are used as the aggregate.

(41) The powder materials are prepared by mixing the compositions shown in following Example of the Table using a ball mill for 30 minutes, and classified with a sieve of 1,000 m.

(42) (Preparation of Liquid Material A)

(43) An acidic colloidal silica having the primary particle diameter of 10 nm (30% of the solid content concentration) was added with N-(-aminoethyl)--amino propyl trimethoxy silane (manufactured by Shinetsu Chemical Co., Ltd.: KBM-603) at the mass ratio of 10:1, and heated to 80 C. and stirred. Thereafter, the pH value was adjusted to 9 by adding 1N of a sodium hydroxide solution. The content of alkali metals (in terms of oxide) is 0.10 wt. %.

(44) (Preparation of Liquid Material B)

(45) Liquid material B was prepared by performing the same treatment as that of the Liquid material A and adjusting the pH value to be 7. In the Liquid material B, the content of alkali metals (in terms of oxide) is 0.01 wt. %.

(46) (Preparation of Liquid Material C)

(47) Liquid material C was prepared by performing the same treatment as that of the Liquid material A and adjusting the pH value to be 11. In the Liquid material C, the content of alkali metals (in terms of oxide) is 0.60 wt. %.

(48) (Preparation of Liquid Material D)

(49) Liquid material D was prepared by performing the same treatment as that of the Liquid material A and adjusting the pH value to be 8. In the Liquid material D, the content of alkali metals (in terms of oxide) is 0.01 wt. %.

(50) (Preparation of Liquid Material E)

(51) Liquid material E was prepared by performing the same treatment as that of the Liquid material A and adjusting the pH value to be 10. In the Liquid material E, the content of alkali metals (in terms of oxide) is 0.20 wt. %.

(52) (Preparation of Liquid Material F)

(53) A raw material was prepared by adding sodium aluminate to commercially available sodium silicate aqueous solution which is a base material and then the raw material was warmed/heated to prepare a colloidal silica aqueous solution. In this colloidal silica aqueous solution, the molar ratio of Al.sub.2O.sub.3/SiO.sub.2 was adjusted to 0.001. In this colloidal silica aqueous solution, the primary particle diameter is adjusted to 10 nm by controlling the particle diameter of the silica in a concentration process of the ion exchange, the solid content concentration is adjusted to 30% and the pH value is adjusted to 9 by adding an alkali metal. The content of alkali metals (in terms of oxide) is 0.1 wt. %.

(54) (Preparation of Liquid Material G)

(55) Liquid material G was prepared by performing the same almina treatment as that of the Liquid material F using the colloidal silica used in the Liquid material F and adjusting the pH value to be 7. In the Liquid material G, the content of alkali metals (in terms of oxide) is 0.02 wt. %.

(56) (Preparation of Liquid Material H)

(57) Liquid material H was prepared by performing the same almina treatment as that of the Liquid material F using the colloidal silica used in the Liquid material F and adjusting the pH value to be 12. In the Liquid material H, the content of alkali metals (in terms of oxide) is 0.80 wt. %.

(58) (Preparation of Liquid Material I)

(59) Liquid material I was prepared by performing the same alumina treatment as that of the Liquid material F using the colloidal silica used in the Liquid material F and adjusting the pH value to be 8. In the Liquid material I, the content of alkali metals (in terms of oxide) is 0.01 wt. %.

(60) (Preparation of Liquid Material J)

(61) Liquid material J was prepared by performing the same almina treatment as that of the Liquid material F using the colloidal silica used in the Liquid material F and adjusting the pH value to be 10. In the Liquid material J, the content of alkali metals (in terms of oxide) is 0.20 wt. %.

(62) (Preparation of Liquid Material K (Colloidal Silica Aqueous Solution for the Comparative Example))

(63) In the Comparative Examples, an aqueous solution including a colloidal silica which was not cation-treated (manufactured by JGC Catalysts and Chemicals Ltd: SI-30) was used. The primary particle diameter is 11 nm and the solid content concentration is 30%. This aqueous solution was used as Liquid material K.

(64) (Measurements of Initial Curing Time, Compression Strength and Crack-Peeling Test)

(65) Investment materials were prepared by using the powder materials and the liquid materials according to the composition list of following Examples and Comparative Examples. The prepared investment materials were performed with Initial Curing time, Compression strength and Crack-peeling test according to JIS T 6608:2001 (Phosphate-based dental investment material). Because the present disclosure relates to an investment material for pressing, Crack-peeling test was performed in ringless state. The rating criteria of Crack-peeling test were as follow: : no crack-peeling; : there is slight crack, but there is no hindrance in pressing; and x: there is a crack which makes performing the pressing impossible.

(66) (Evaluation of Reaction Layer)

(67) Wax plates having a dimension of 10 mm by 10 mm by 1 mm (thickness) were prepared and planted on a ring base for pressing.

(68) The investment materials prepared by using the powder materials and the liquid materials according to the composition list of following Examples and Comparative Examples were kneaded by a laboratory mixer (manufactured by SHOFU INC.) for 60 seconds and injected into a ring for pressing. After 20 minutes from the inventiment, they were thrown into a furnace of 850 C. to hold for 1 hour. Thereafter, a lithium disilicate ingot vintage LD (manufactured by SHOFU INC.) was pressed according to the press schedule described in the instruction book. After finishing the press, the moded body was dug out and the existence of the reaction layer was visually evaluated. The surface attached with the reaction layer was scanned by the three dimensional laser microscope and the area of the reaction layer was calculated. The case that the surface of the molded body has no reaction layer is defined as 100% of score and the case that the reaction layer is attached to the entire surface of the molded body is defined as 0% of score. Based on these definition, the ratio of the area of the reaction layer to the the surface of the molded body was evaluated.

(69) TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4 Powder Aggregate Cristobalite 30 30 25 25 Material compounded Quartz 40 40 35 35 amount zirconium silicate 5 5 5 5 [wt. %] zirconia 5 5 5 5 Binding Magnesium 6 6 10 10 material oxide compounded Ammonium 14 14 20 20 amount dihydrogenphosphate [wt. %] Liquid Type of liquid material A F A F material Mixing ratio of Liquid material (Quantity of 20 20 20 20 Liquid material per 100 g of Powder material [mL] Initial Curing time [Min] 9.0 9.0 10.0 10.0 Compression strength [MPa] 15.3 14.3 18.3 17.4 Crack-peeling test Evaluation of Reaction layer of 66 75 52 78 press-molded body

(70) TABLE-US-00002 TABLE 2 Example 5 Example 6 Example 7 Example 8 Powder Aggregate Cristobalite 30 30 30 30 Material compounded Quartz 40 40 40 40 amount zirconium silicate 5 5 5 5 [wt. %] zirconia 5 5 5 5 Binding Magnesium 6 6 6 6 material oxide compounded Ammonium 14 14 14 14 amount dihydrogenphosphate [wt. %] Liquid Type of liquid material B C G H material Mixing ratio of Liquid material 18 22 18 22 (Quantity of Liquid material per 100 g of Powder material [mL] Initial Curing time [Min] 13.0 5.0 14.0 5.0 Compression strength [MPa] 9.5 10.1 12.1 12.8 Crack-peeling test Evaluation of Reaction layer of 66 55 62 58 press-molded body

(71) TABLE-US-00003 TABLE 3 Example 9 Example 10 Example 11 Example 12 Powder Aggregate Cristobalite 30 30 30 30 Material compounded Quartz 40 40 40 40 amount zirconium silicate 5 5 5 5 [wt. %] zirconia 5 5 5 5 Binding Magnesium 6 6 6 6 material oxide compounded Ammonium 14 14 14 14 amount dihydrogenphosphate [wt. %] Liquid Type of liquid material D E I J material Mixing ratio of Liquid material 20 20 20 20 (Quantity of Liquid material per 100 g of Powder material [mL] Initial Curing time [Min] 9.0 7.0 9.0 7.0 Compression strength [MPa] 9.0 10.5 8.6 10.5 Crack-peeling test Evaluation of Reaction layer of 66 65 75 70 press-molded body

(72) TABLE-US-00004 TABLE 4 Example 13 Example 14 Example 15 Powder Aggregate Cristobalite 30 30 30 Material compounded Quartz 26 46 29 amount zirconium silicate 5 5 5 [wt. %] zirconia 5 5 5 Binding Magnesium oxide 20 6 6 material compounded Ammonium 14 8 25 amount dihydrogenphosphate [wt. %] Liquid Type of liquid material A A A material Mixing ratio of Liquid material (Quantity of 20 20 20 Liquid material per 100 g of Powder material [mL] Initial Curing time [Min] 6.0 12.0 13.0 Compression strength [MPa] 10.1 9.6 11.0 Crack-peeling test Evaluation of Reaction layer of 81 95 61 press-molded body

(73) TABLE-US-00005 TABLE 5 Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Powder Aggregate Cristobalite 30 25 30 30 Material compounded Quartz 40 35 42 24 amount zirconium silicate 5 5 5 5 [wt. %] zirconia 5 5 5 5 Binding Magnesium 6 10 4 22 material oxide compounded Ammonium 14 20 14 14 amount dihydrogenphosphate [wt. %] Liquid Type of liquid material K K F F material Mixing ratio of Liquid material (Quantity of 20 20 20 20 Liquid material per 100 g of Powder material [mL] Initial Curing time [Min] 8 8 16 4 Compression strength [MPa] 15.7 16.9 5.6 16.2 Crack-peeling test X X Evaluation of Reaction layer of 22 9 Impossible Impossible press-molded body to press to press

(74) TABLE-US-00006 TABLE 6 Compar- Compar- ative ative Example 5 Example 6 Powder Aggregate Cristobalite 30 30 Material compounded Quartz 48 26 amount [wt. %] zirconium 5 5 silicate zirconia 5 5 Binding Magnesium 6 6 material oxide compounded Ammonium 6 28 amount [wt. %] dihydrogen- phosphate Liquid Type of liquid material K K material Mixing ratio of Liquid material (Quantity of 20 20 Liquid material per 100 g of Powder material [mL] Initial Curing time [Min] 4 18 Compression strength [MPa] 4.8 10.9 Crack-peeling test x Evaluation of Reaction layer of press-molded Impossible 29 body to press
(Consideration)

(75) In Examples 1 to 15 in which an area of a reaction layer was 50% or less of the surface of a press-molded body, and the scores were 50 or more. In these cases, they can be clinically used without any problem. On the other hand, the score in Comparative example 1 was 22, the score in Comparative example 2 was 9, and the score in Comparative example 6 was 29. The scores in these Comparative examples were very low and therefore a problem for a clinical use may occur. In comparative examples 3-5, it was impossible to perform an evaluation of a reaction layer in a crack-peeling test because of generation of a crack which makes it impossible to press.

(76) [Effect]

(77) As shown in the above result, the present disclosure provides a phosphate-based dental investment material substantially containing no reaction layer even if phosphate-based dental investment material is prepared by press molding a disilicate ingot.

(78) With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context.

(79) Although the description herein has been given with reference to the drawings and embodiments, it should be noted that those skilled in the art may make various changes and modifications on the basis of this disclosure without difficulty. Accordingly, any such changes and modifications are intended to be included in the scope of the embodiments.