JP2008214748A - Dental casting alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dental casting alloy containing ≥40% of Au and Ag in total as a base alloy, the alloy enabling the occurrence of cavities to be suppressed even when not containing Zn and enabling a degradation in the mechanical characteristics of a prosthesis material to be prevented, particularly, a dental casting alloy capable of remarkably exhibiting the above actions even if repeated casting is performed. <P>SOLUTION: The dental casting alloy contains ≥40%, by mass, of Au and Ag in total. The alloy does not contain Zn, but contains ≤10% (not including 0%) of Ga. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a dental casting alloy used as a raw material when producing a dental prosthesis by a casting method, and specifically contains Au (gold) and Ag (silver) in a total of 40% or more. The present invention relates to an alloy for dental casting.

  As an alloy for dental casting used when producing a dental prosthesis, for example, gold-silver-palladium alloy, silver alloy, gold alloy, nickel-chromium alloy, cobalt-chromium alloy, titanium alloy and the like are known.

  When producing a dental prosthesis for adults, an alloy for dental casting containing Au is used as a raw material so as to withstand long-term use. However, when a dental prosthesis is made of pure gold, the strength of the prosthesis is insufficient and cannot be used for a long time. Moreover, it becomes remarkably expensive. Therefore, in order to increase the strength of the prosthesis and to reduce the price, generally, an Au-Ag dental casting alloy obtained by alloying Ag that is solid-solved at any mixing ratio with respect to Au is used as a dental prosthesis. Used as a raw material.

  As a dental casting alloy containing Au and Ag as base metals, for example, Patent Document 1 proposes a dental casting alloy containing Au, Ag, Pd and In. This document describes that discoloration resistance can be ensured by controlling the mixing balance of Au and In without causing castholes and alloy composition segregation.

  By the way, when a dental casting alloy containing Au and Ag is melted in the process of producing a prosthesis, Ag in the alloy is oxidized to form an oxide, and a slag film is formed on the surface of the molten metal. This slag film is mixed in the molten metal at the time of casting, and deteriorates the flow of the molten metal (molten metal) in the mold. Further, when slag is mixed into the molten metal, a cast hole is generated in the prosthesis. When a cast hole is generated, mechanical properties (particularly strength and elongation) of the prosthesis deteriorate.

  In order to prevent such oxidation of Ag, it is known to contain Zn as an antioxidant in the alloy. Zn acts as a deoxidizer in the alloy and prevents Ag from oxidizing during melting. Zn also has the effect of improving the discoloration resistance of the prosthesis. However, when Zn was contained, some patients developed Zn allergy (Non-patent Document 1).

  By the way, since the alloy for dental casting containing Au is expensive, an alloy that is not used as a prosthesis (for example, an alloy remaining in a feeder or a runner) is melted again and used. However, when melting and casting are repeated, the mechanical properties (particularly strength and elongation) of the prosthesis may be lowered, and improvement of the mechanical properties by repeated use has been demanded.

Although it is an alloy for dental casting that does not contain Au, Patent Document 2 discloses an Ag alloy for dental casting that contains In, Zn, Ga, Pd, and Fe, and the balance is made of Ag. Here, it is disclosed that both Zn and Ga are used in order to prevent oxidation during casting of the alloy and to prevent deterioration of physical properties of the alloy during repeated casting.
JP 2003-155528 A JP-A-7-76744 "Dental and metal allergy", Masayuki Inoue, Dental Diamond Co., Ltd., issued on November 1, 1993, P.I. 12

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a casting alloy containing 40% or more of Au and Ag as a base alloy in a total amount, without containing Zn. An object of the present invention is to provide a dental casting alloy that can suppress the formation of nests and can prevent deterioration of mechanical properties of the prosthesis. In particular, it is an object of the present invention to provide a dental casting alloy that can exert the above-described effects remarkably even when repeated casting is performed.

  The dental casting alloy according to the present invention that has been able to solve the above-mentioned problems is a dental casting alloy containing Au and Ag, the total of which is 40% (meaning mass%, hereinafter the same) or more. The alloy does not contain Zn and has a gist in that it contains 10% or less (not including 0%) of Ga.

The alloy for dental casting of the present invention is further added as another element,
(A) Pt: 10% or less (not including 0%), Pd: 30% or less (not including 0%) and Ir + Ru + Rh: 1% or less in total (not including 0%), selected from the group consisting of At least one platinum group element,
(B) Cu: 25% or less (excluding 0%),
(C) In: 30% or less (excluding 0%),
(D) An element selected from the group consisting of B, P, Ca, Sn, Mg, Al, Si, Mn, Fe, Zr, Ge, Y, Re, and Ti is 3% or less in total (including 0%) Absent),
Etc. may be contained.

  According to the present invention, a dental casting alloy containing a total of 40% or more of Au and Ag as a base alloy contains a predetermined amount of Ga to oxidize Ag during melting without adding Zn. Can be prevented. Therefore, generation | occurrence | production of slag can be suppressed and the cast hole which generate | occur | produces in a prosthesis can be reduced. Since the Ga-containing Au—Ag-containing alloy of the present invention does not contain Zn, it can be applied to patients with Zn allergy. In addition, since Ga can exhibit an Ag oxidation suppression effect over a long period of time compared to Zn, slag is hardly generated even when repeated melting and casting, and the mechanical properties (particularly strength and elongation) of the prosthesis deteriorate. Can be prevented. Furthermore, since Ga also has an effect of improving discoloration resistance, it is possible to exhibit an effect of preventing slag generation and improving mechanical properties by repeated use, which is extremely remarkable than Zn, while maintaining all the excellent effects of Zn. It is extremely useful.

  The dental casting alloy of the present invention is characterized in that it contains Ga instead of Zn with respect to a base alloy containing both Au and Ag.

  In addition, although the kind of base alloy differs in patent document 2 mentioned above, Zn has the effect which prevents the oxidation at the time of casting of an alloy, and has the effect which prevents the deterioration of the physical property of the alloy at the time of repeated casting, Ga is Zn and Although described to have a similar action, it is not at all intended to provide a Zn-less alloy as in the present invention. Also, according to the experiments by the present inventors, it was revealed that the deoxidation effect of Ga far exceeds the deoxidation effect of Zn, unlike the conventional recognition. That is, as will be clarified in the examples to be described later, the deoxidation effect of Ga is continuously exhibited even after repeated melting and casting, so that the generation of slag can be suppressed over a long period of time. Degradation of mechanical properties (especially strength and elongation) can be minimized. On the other hand, the deoxidizing action of Zn decreases as casting is repeated, and slag is generated as shown in the examples to be described later, so that the mechanical properties (particularly strength and elongation) of the prosthesis deteriorate. .

  Further, by containing Ga instead of Zn, the melting point of the dental casting alloy can be lowered as compared with the case of containing Zn, and the casting workability can be improved. That is, the melting point of Ga is 29.8 ° C., whereas the melting point of Zn is 419 ° C., so the Ga-containing dental casting alloy has a lower melting point. If the melting point of the dental casting alloy is lowered, the castable temperature range is widened, so that the dental casting alloy can be cast even when the melting temperature is not properly controlled. Therefore, it becomes easy to perform casting work.

  In order to effectively exhibit the above-described effects of Ga, the Ga content is preferably 0.05% or more. More preferably, it is 0.1% or more. However, since the melting point of the dental casting alloy is too low even if it is contained excessively, it tends to be deformed by heat treatment after casting (usually heated to about 400 to 700 ° C.) performed to ensure the strength of the prosthesis. . Therefore, the Ga content is set to 10% or less in consideration of practicality. Preferably it is 8% or less, More preferably, it is 5% or less.

  The dental casting alloy of the present invention contains Au and Ag as a base alloy, and the total of these satisfies 40% or more. This is because, as will be described later, in order to effectively exhibit both the corrosion resistance improving action of Au and the strength improving action of Ag, it is preferable to use the above base alloy.

  Among the base alloys, Au is extremely excellent in corrosion resistance, and therefore has excellent discoloration resistance in the oral cavity. Moreover, since Au has good ductility, it is possible to improve the elongation of the prosthesis and prevent the prosthesis from being damaged. The specific lower limit of the content of Au varies depending on the purpose of use and application, but is, for example, about 5% or more (particularly 10% or more). The upper limit of the Au content is not particularly limited, but since Au is an element having low strength, it is preferably set to, for example, about 85% or less from the viewpoint of ensuring strength as a prosthesis.

  On the other hand, among the base alloys, Ag is an element that is easily alloyed with Au. In particular, in order to ensure the strength of the prosthesis, it is preferable to contain approximately 35% or more. More preferably, it is 40% or more. The upper limit of the Ag content is not particularly limited. However, since Ag is easily sulfided and discolored in the oral cavity, for example, the upper limit is preferably 65% or less.

Here, as a dental casting alloy containing Au and Ag as a base alloy, for example,
(1) “Gold alloy for dental casting” of JIS T6116 in which Au is 65% or more and the total of Au and platinum group elements (Pd, Pt, Ir, Ru, and Rh) satisfies 75% or more,
(2) “A dental casting alloy having a noble metal content of 25% or more and less than 75%” in JIS T6122, which satisfies the sum of Au and platinum group elements of 25% or more and less than 75%;
(3) JIS T6106 “gold and silver palladium alloy for dental casting” that satisfies Au of 12% or more, Pd of 20% or more, and Ag of 40% or more, or (4) Au of 20% or less (excluding 0%) ), An alloy satisfying Ag of 40% or more,
Etc. are applicable. As shown in the examples described later, in any alloy system, an excellent deoxidizing action due to the addition of Ga is effectively exhibited.

As described above, the dental casting alloy of the present invention contains at least Au, Ag, and Ga, and can also tolerate impurities inevitably mixed in the casting process. The alloy of the present invention is an Au-Ag alloy containing Ga, and the balance may be made of inevitable impurities, but if necessary,
(A) Pt: 10% or less (not including 0%), Pd: 30% or less (not including 0%), and Ir + Ru + Rh: 1% or less in total (not including 0%) At least one platinum group element,
(B) Cu: 25% or less (excluding 0%),
(C) In: 30% or less (excluding 0%),
(D) 3% or less (not including 0%) in total of elements selected from the group consisting of B, P, Ca, Sn, Mg, Al, Si, Mn, Fe, Zr, Ge, Y, Re, and Ti ),
Or the like. By containing these selective elements, the following characteristics can be further improved.

  (A) Platinum group elements (Pt, Pd, Ir, Ru, Rh) are all elements that increase the strength of the prosthesis, and each contains alone or in combination of two or more selected arbitrarily. May be. Preferable content of each element is as follows.

[Pt (platinum): 10% or less (not including 0%)]
Pt is an element that increases the strength of the prosthesis and also increases hardness and discoloration resistance. However, when it contains excessively, the melting temperature of an alloy will become high, and a castable temperature range will become narrow. In addition, excessive content increases the cost. Therefore, the Pt content is 10% or less. Preferably it is 5% or less, More preferably, it is 2% or less. Pt exhibits its effect when added in a small amount, but preferably 0.05% or more.

[Pd (palladium): 30% or less (excluding 0%)]
Pd is an element that exhibits the same effect as Pt, but is relatively inexpensive compared to Pt. However, if contained excessively, the melting temperature of the alloy becomes too high, and cracking is likely to occur when the molten alloy solidifies and shrinks. Accordingly, the Pd content is 30% or less. Preferably it is 25% or less. Pd exhibits its effect when added in a small amount, but is preferably contained in an amount of 10% or more.

[Ir (iridium) + Ru (ruthenium) + Rh (rhodium): 1% or less in total (not including 0%)]
Ir, Ru, and Rh are all diffused and dissolved in the Pt and Pd matrix, and the Pt and Pd crystals are refined to disperse the stress when stress is applied from the outside, and the mechanical properties of the prosthesis It is an element that improves the properties (strength, elongation, hardness). However, since Ir, Ru, and Rh have low solubility in Au and Ag, segregation is likely to occur when the total amount of these elements exceeds 1%, and the strength, elongation, and toughness of the prosthesis decrease. Therefore, the total amount of Ir, Ru and Rh is 1% or less. Preferably it is 0.8% or less, More preferably, it is 0.5% or less. The total amount of Ir, Ru and Rh is preferably 0.005% or more. Ir, Ru, and Rh can be used alone or in combination of two or more selected arbitrarily.

  (B) Cu is an element that is alloyed with Au to increase the strength of the prosthesis. In particular, the strength is increased by heat-treating the prosthesis. However, since Cu is easily oxidized, slag is generated when Cu is excessively contained. Therefore, the Cu content is preferably 25% or less. Preferably it is 20% or less. Cu exhibits the above effect with a small amount of addition, but it is preferable to contain 5% or more.

  Examples of the dental casting alloy of the present invention include Au: 20% or less (excluding 0%), Ag: 40% or more, as an example containing both the platinum group element (a) and Cu (b). , Pd: 30% or less (not including 0%), Cu: 25% or less (not including 0%), Au—Ag—Ga—platinum group element—Cu alloy.

  (C) As described above, Pt and Pd have the effect of improving the discoloration resistance of the prosthesis, but Pt and Pd are relatively expensive elements. Therefore, when reducing the content of Pt or Pd, it is preferable to positively contain In.

  In (indium) has the effect of improving the resistance to discoloration in the oral cavity by improving the sulfidation resistance of the dental casting alloy by a synergistic action with Pt and Pd. In also exhibits a deoxidizing effect by synergistic action with Ga. In also has the effect | action which lowers melting | fusing point of a dental casting alloy and improves casting workability | operativity. However, when In is contained excessively, the melting point is excessively lowered. Therefore, the In content is preferably 30% or less. Preferably it is 25% or less, More preferably, it is 10% or less, More preferably, it is 3% or less. In exhibits its effect when added in a small amount, but preferably contains 0.5% or more.

  (D) B, P, Ca, Sn, Mg, Al, Si, Mn, Fe, Zr, Ge (germanium), Y (yttrium), Re (rhenium), and Ti promote Ga deoxidation. Since it is an element and generation of slag can be further suppressed over a long period of time, it is possible to prevent the formation of a cast hole and to prevent the mechanical properties (particularly strength and elongation) of the prosthesis from deteriorating. However, if these deoxidizing elements are contained excessively, the metal structure is distorted and the mechanical properties of the dental casting alloy tend to deteriorate, and the mechanical properties required for the dental casting alloy cannot be satisfied. is there. Therefore, the total of these deoxidizing elements is preferably 3% or less. Preferably it is 2% or less, More preferably, it is 1% or less. The deoxidizing element exhibits its effect when added in a small amount, but is preferably contained in an amount of 0.001% or more. The above deoxidizing elements can be used alone or in combination of two or more arbitrarily selected.

As described above, the dental casting alloy of the present invention contains Au—Ag—Ga as an essential component, and further contains the above-mentioned selective elements, and its production method is not particularly limited. Good. In addition, when adding said selective element, you may add the elemental element of a selective element to the Au-Ag-Ga alloy used as a base, and may add with the form of a compound or an alloy. For example, B is a boride [eg, calcium boride (CaB ₆ )], P is a phosphorus compound [eg, copper phosphide (Cu ₃ P, CuP ₂ , Cu ₃ P ₂ )], and Ca is a calcium compound. You may add and adjust content of each element. Further, P content may be adjusted by adding P in the form of phosphor bronze (an alloy in which a small amount of P is added to Cu-Sn bronze).

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples are not intended to limit the present invention, and may be implemented with appropriate modifications within a range that can meet the purpose described above and below. These are all possible and are within the scope of the present invention.

[Example 1]
Alloys for dental casting were prepared at the blending ratios shown in Tables 1 and 2 below, and the obtained alloys were melted and then cast to evaluate the occurrence of slag and castability. For Au, Ag, Ga, and In, those having a purity of 99.99% or more are used, and for Pd, Pt, and Cu, those having a purity of 99.95% or more are used. Among them, the one with as high purity as possible was used. In Table 2, No. 31 and no. For the 45 dental casting alloy, phosphorous copper (Cu ₃ P) was added to adjust the amount of Cu and the amount of P. In Table 2, No. For 32 dental casting alloys, calcium borate (CaB ₆ ) was added to adjust the Ca content and B content.

  Specifically, the dental casting alloy is placed in a ceramic crucible dish, and the alloy is heated to about 1000 to 1100 ° C. with flame (city gas + compressed air) without adding flux (antioxidant). Melted. The molten alloy was cast by the following procedure to obtain a cast product. A cristobalite mold material was used as the mold material, and a wax mold (10 mm × 30 mm × 0.5 mm) was embedded in the mold material and sufficiently cured. The mold template obtained by curing was placed in an electric furnace at 700 ° C. and dewaxed to prepare a mold. The obtained mold was attached to a dental horizontal centrifugal casting machine, and a molten alloy was injected and cast to obtain a plate-like cast product. Ten castings were produced.

  About the presence or absence of slag generation | occurrence | production, when the said alloy was fuse | melted in the crucible dish, it was confirmed visually whether slag generate | occur | produces on the surface of a molten metal. The results of evaluating the presence or absence of slag generation are shown in Tables 1 and 2 below. The state without slag generation corresponds to evaluation level 0 in FIG. 1 described later, and the state with slag generation corresponds to evaluation levels 1 to 4 in FIG. 1 described later.

  In addition, the appearance of the plate-like cast product obtained by casting is visually observed to check whether the cast product is deformed and whether there is a cast hole, and the castability is evaluated according to the following criteria. did. The evaluation results are shown in Tables 1 and 2 below.

[Castability evaluation criteria]
◎ (Pass): No problem for all 10 castings.
○ (Accepted): Deformation or casting hole was observed in one of 10 castings.
Δ (failure): Among 10 cast products, 2 to 3 were deformed or found.
X (failed): Deformation and casting voids were observed in 4 or more of 10 castings.

  The following Table 1 and Table 2 can be considered as follows. No. 1-27, no. Nos. 31 to 47 are Zn-free Au—Ag alloys (examples of the present invention) containing Ga, and no slag was generated during melting, and the castability was also good. Moreover, since they do not contain Zn, they can also be applied to patients with Zn allergies.

  In particular, no. Since Nos. 31 to 47 further contain a deoxidizing element, the generation of slag could be further suppressed over a long period of time, and no cast hole was observed in the cast product. That is, No. 2 in Table 2. 31 and 32 are No. 1 in Table 1. It is an example in which a deoxidizing element is further added based on the dental casting alloy shown in FIG. 18, and it can be seen that the castability can be further improved. No. in Table 2 33 to 44 are No. 1 in Table 1. This is an example in which the dental casting alloy shown in FIG. 19 is used as a base and a deoxidizing element is further added. It can be seen that the castability can be further improved.

  In contrast, no. 28 and No. 29 is an Au-Ag alloy (comparative example) containing neither Ga nor Zn, and slag was generated at the time of melting, and a cast hole was generated in the cast product. In particular, no. No. 29 has a high Ag content of 48% and a high Cu content of 20%. Slag was more likely to occur during melting than in the case of 28, and the castability was poor.

  In addition, No. No. 30 is an Au—Ag alloy (conventional example) that contains Zn and does not contain Ga, and can prevent the generation of slag at the time of melting, and therefore has relatively good castability. However, it cannot be applied to patients with Zn allergy.

[Example 2]
In Example 1 above, No. 1 is shown in Table 1 above. 19, no. 29, no. The dental casting alloy shown as 30 was placed in a crucible dish, and the alloy was melted and then solidified, and the presence or absence of slag was visually confirmed when this melting + solidification was repeated 10 times. Melting conditions were the same as in Example 1, and the alloy was heated to about 1000 to 1100 ° C. with a flame (city gas + compressed air) without adding flux (antioxidant) and melted for about 1 minute. The molten alloy was solidified in a reducing flame while still in the crucible dish. In addition, no new alloy is added at the time of melting.

  The presence or absence of slag generation was evaluated in 9 stages according to the following visual criteria. The photograph which image | photographed the production | generation state of the slag applicable to each reference | standard is shown in FIG. 1 as drawing substitute photograph. In addition, when melting + solidification is repeated 10 times, an example of the present invention has an evaluation score of 0.5 or less based on the following criteria.

[Standard]
0: No slag is generated.
0.5: A slag film was thinly formed and covered less than about 25% of the molten metal surface.
1: The slag film | membrane produced | generated thinly and had covered about 25% or more and less than 50% of the hot_water | molten_metal surface.
1.5: A thin slag film was formed, covering about 50% of the molten metal surface.
2: The slag film | membrane produced | generated thinly and had covered about 50% or more and less than 75% of the molten metal surface.
2.5: The slag film was thinly formed and covered about 75% or more of the molten metal surface.
3: A slag film was formed thick, and cracks were also observed in the slag film. The slag film covered less than about 50% of the hot water surface. Moreover, the viscosity of the molten metal was high.
3.5: A thick slag film was formed, and cracks were also observed in the slag film. The slag film covered about 50% of the hot water surface. Also, the viscosity of the molten metal was high.
4: The slag film | membrane produced | generated thickly and the crack was recognized by the said slag film | membrane. The slag film covered about 50% or more of the hot water surface. Moreover, the viscosity of the molten metal was high.

  FIG. 2 shows the results of evaluating the presence or absence of slag generation when repeated experiments are performed. In FIG. The result of No. 19 (example of the present invention) is ○, The result of No. 29 (comparative example) is indicated by ■ and No. 29. The results for 30 (conventional example) are indicated by ▲.

  It can be considered as follows from FIG. No. Since the alloy of 19 (◯) contains Ga, even when melting and solidification are repeated, slag is hardly generated during melting.

  In contrast, no. Since the 29 (■) alloy contained neither Ga nor Zn, slag was generated during melting. No. Since the alloy of 30 (▲) contains Zn, the generation of slag can be suppressed even if the melting and solidification are repeated about 3 to 4 times, but when it is repeated 5 times or more, the slag is suddenly generated. . Therefore, it is considered that when the Zn-containing alloy is repeatedly used, the strength of the obtained prosthesis gradually decreases.

  From the above experimental results, it was proved that the use of an Au—Ag alloy containing Ga instead of Zn as in the present invention markedly improves the slag generation prevention effect particularly during repeated use, as compared with the Zn-containing alloy. .

[Example 3]
In Table 1 above, no. 19 (invention example), No. 29 (comparative example), no. A dental casting alloy shown as 30 (conventional example) was melted (melted once), and a tensile test was performed using a cast product obtained by casting under the same conditions as in Example 1 above. As described in JIS T6106, the tensile test was performed based on JIS Z2241, and the tensile strength and elongation were measured. The measurement results are shown in Table 3 below.

  Further, an alloy remaining after casting (for example, an alloy remaining in a feeder or runner) is recovered, and the recovered alloy and a dental casting alloy having the same composition as that used for casting are collected on a mass basis. After mixing at a ratio of 1: 1 and melting, a second casting was performed. These operations were repeated 10 times, and a tensile test was performed using the cast product obtained by the 10th casting. The tensile test is performed under the same conditions as described above, and the measurement results of tensile strength and elongation are shown in Table 3 below.

  The strength change was calculated by comparing the tensile strength of the casting obtained by the first casting with the tensile strength of the casting obtained by the tenth casting. The change in elongation was calculated in the same manner. The calculation results are also shown in Table 3 below. In practice, it was determined that the tensile strength was 550 MPa or more and the elongation was 5% or more.

  From Table 3 below, it can be considered as follows. No. Since the alloy No. 19 contains Ga, slag is hardly generated even when melting and casting are repeated, and the tensile strength and elongation are hardly deteriorated. In Table 1, No. 2, no. 5, no. 14, no. 17, no. 20, no. 22, no. 27, No. 2 in Table 2. 31, no. 35, no. A similar experiment was conducted on the 45 examples, but no slag was produced and no deterioration in physical properties was observed.

  No. Since the alloy of 29 does not contain Ga, slag was generated at the time of melting, and the tensile strength was reduced by casting this slag into a cast product. This phenomenon becomes more prominent as casting is repeated. When casting is repeated 10 times, the strength of the cast product decreases to about 200 MPa. In addition, No. Since the alloy No. 29 had a low tensile strength and was brittle, the elongation could not be measured.

  No. The alloy No. 30 is a conventional example containing Zn, and the generation of slag can be suppressed at the first melting, and the mechanical properties (strength and elongation) of the obtained cast product are good. However, as casting was repeated, slag accumulated in the alloy, and the tensile strength of the cast product obtained by the tenth casting was reduced by about 14% and the elongation was reduced by about 57%.

  From the above results, it was proved that Ga has a much better mechanical property improving effect under repeated experiments than Zn.

[Example 4]
As a mock test for clinical use, a discoloration test defined in JIS T6106 was performed. That is, in Table 1 above, no. 19 (invention example), No. 29 (comparative example), no. The cast alloy obtained by melting the dental casting alloy shown as 30 (conventional example) and casting under the same conditions as in Example 1 above is immersed in a corrosive solution prepared for intraoral mounting and discolored. A test was conducted. As the corrosive solution, 50 ml of an aqueous solution containing 0.1% by mass of sodium sulfide was used, and the cast product was immersed for 3 days while the temperature of the aqueous solution was controlled at 37 ± 2 ° C. The change in color of the cast product before and after the discoloration test was measured with a color difference meter (Olympus "CR-200"). The color change is represented by hue, brightness, and saturation based on the “color display method” defined in JIS Z8721. The results are shown in Table 4 below.

  Further, the cast product after the color change test was visually observed, and the color change was also visually determined.

  From Table 4, it can be considered as follows. No. No. 19 uses Pd and In in combination, and thus has a synergistic effect and has improved sulfidation resistance. Therefore, it has excellent discoloration resistance. No. Since 29 did not contain In, it was poor in sulfidation resistance, and discoloration was observed. It is thought that the occurrence of a cast hole is also a cause of discoloration. No. No. 30 did not contain In, but it contained Zn, so that although the sulfur resistance was somewhat improved, some discoloration was observed.

  From the above experimental results, it was proved that the corrosion resistance improving action by In or Pd is also effectively exhibited in the Ga-containing Au—Ag alloy of the present invention.

FIG. 1 is a drawing-substituting photograph showing a standard for evaluating the generation state of slag. FIG. 2 is a graph showing the results of evaluating the presence or absence of slag generation.

Claims (5)

An alloy for dental casting containing Au and Ag, the total of which is 40% (meaning mass%, the same applies hereinafter),
This alloy does not contain Zn, and contains 10% or less (not including 0%) of Ga. As other elements,
Pt: 10% or less (excluding 0%),
Pd: 30% or less (excluding 0%) and Ir + Ru + Rh: 1% or less in total (excluding 0%),
The dental casting alloy according to claim 1, comprising at least one platinum group element selected from the group consisting of:   The dental casting alloy according to claim 1 or 2, further comprising Cu: 25% or less (not including 0%) as another element.   The dental casting alloy according to any one of claims 1 to 3, further comprising In: 30% or less (not including 0%) as another element. As other elements,
Contains 3% or less (excluding 0%) in total of elements selected from the group consisting of B, P, Ca, Sn, Mg, Al, Si, Mn, Fe, Zr, Ge, Y, Re, and Ti The dental casting alloy according to any one of claims 1 to 4.