RU2303640C1 - Gold-based stomatological alloy - Google Patents

Abstract

FIELD: stomatological materials.

SUBSTANCE: invention relates to stomatology-destination gold-based cast alloys, which are used for manufacturing stomatological structures such as removable clasp dental prostheses. Alloy is composed of, wt %: silver 10-12, platinum 4-5, copper 10-12, zinc 0.6-1.0, iridium 0.05-0.15, and gold in balancing proportion, provided that (Au+Pt+Ir) =75, Ag.Cu=0.9-1.1, Ag/Pt=2.0-2.4, and (Ag+Pt)/(Cu+Zn)=1.2-1.4. Yellowness index is more than 24.

EFFECT: increased corrosion resistance and imparted mechanical properties ensuring rigidity of stomatological structure.

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Description

The invention relates to the field of metallurgy, in particular to noble metals based on gold, which are intended for the manufacture of dental structures, in particular cast clasp removable dentures.

Known thermally hardened alloy based on gold for dentistry (SU 1836474, C22C 5/02, 1993 [1]), containing, wt.%: Gold 75-76, zinc 0.2-0.9, silver 10.5 -12.5, copper - the rest. The alloy has a deep yellow color. The level of mechanical properties of the alloy corresponds to type 3 (durable) according to the international classification ISO 1562: 1993, which is not enough to meet the requirements for clasp prostheses ..

The closest analogue to the proposed alloy is a thermally hardened casting alloy based on gold for dentistry, disclosed in EP 0904765 A2, A61K 6/04, 09/15/1998 / 2 /. The alloy contains, wt.%: Gold 60-90, silver 0-20, palladium 0-7, platinum 0-11, copper 0-20, zinc 0-2, tin 0-1, indium 0-3 and as refining additives iridium 0.001-0.1. Despite the fact that the alloy belongs to the 4th type (heavy-duty) according to the international classification ISO 1562: 1993, it has the following disadvantages. The alloys described in [2] cover a large number of compositions, not all of which have high corrosion resistance, biological inertness, and the necessary color, which is associated with the suboptimal content of platinoids and, in particular, the presence of palladium in the alloy, which discolours yellow alloys in in some cases, as indicated in [2], it causes allergic reactions in individual patients.

The problem to which the invention is directed, is the creation of a high-strength thermally hardened casting alloy based on gold, designed for heavily loaded and thin-walled dental structures, including removable clasp prostheses that work under alternating loads that occur when chewing. In this case, the alloy must meet the following requirements:

- to have an optimal combination of a high yield strength and ductility, which ensures rigidity of the dental structure and high resistance to fatigue damage under the action of alternating loads arising during chewing, especially in the areas of attachment of these structures. According to the combination of mechanical properties, the alloy must meet the requirements of a heavy-duty alloy of the 4th type according to the international classification ISO 1562: 1993.

- have a pronounced yellow color with a yellowness coefficient YI of more than 24 according to the requirements of ASTM E 313-00 (many patients prefer the yellow color of dental constructions that satisfy the above requirement for yellowness).

- possess high corrosion resistance, as well as biological inertness.

The technical result of the proposed invention is to obtain a yellow corrosion-resistant and biologically inert alloy with high mechanical properties that ensure reliability when using a dental structure.

The technical result is achieved by the fact that in a casting alloy based on gold for dentistry containing silver, platinum, copper, zinc and iridium, the components are contained in the following amount, wt.%:

Platinum 4-5; Silver 10-12; Copper 10-12; Zinc 0.6-1.0; Iridium 0.05-0.15, Gold rest,

while the content of the components must satisfy the following conditions:

(Au + Pt + Ir) ≥75 wt.%;

Ag / Cu = 0.9 ÷ 1.1;

Ag / Pt = 2.0 ÷ 2.4;

(Ag + Pt) / (Cu + Zn) = 1.2 ÷ 1.4,

moreover, the alloy has a yellowness coefficient YI of more than 24 according to ASTM E 313-00.

With a total content of gold, platinum and iridium (Au + Pt + Ir) ≥75 wt.%, The alloy provides not only the optimal combination of mechanical properties due to solid-solution hardening (type 4 heavy-duty alloys according to the international classification ISO 1562: 1993), but and high corrosion and biological resistance due to the high corrosion resistance of gold and major alloying noble metals. Platinoids (in the claimed alloy of platinum and iridium) can suppress the yellow color of gold. Therefore, the content of platinoids in the amount of 4.05-5.15 wt.% (In a gold-based alloy containing 70-75 wt.% Au) is chosen so that when optimal mechanical properties are achieved, the alloy does not discolor and yellowness is ensured YI over 24.

With the introduction of silver and copper in amounts of Ag / Cu = 0.9 ÷ 1.1, the strength characteristics also increase and the greatest wear resistance and hardness are achieved.

The ratios of silver and platinum (Ag / Pt = 2.0 ÷ 2.4) and copper with zinc (Ag + Pt) / (Cu + Zn) = 1.2 ÷ 1.4 were selected in such a way as to balance possible color shifts from yellow towards red, green and white. Moreover, all of these alloying elements are involved in the hardening of the alloy.

In addition, the selected ratio of silver to platinum largely determines the level of coefficient of thermal expansion (CTE), which should be in the range of 13.5-14.5 · 10 ^-6 K ^-1 .

Example.

To obtain the claimed alloy, charge materials were placed in a graphite crucible and melted in a furnace of a dental foundry. Then the melt was cast into a flask molded to obtain samples for mechanical testing. The samples were subjected to heat treatment according to the quenching and quenching scheme with subsequent aging. Then, physical and mechanical tests were carried out, the results of which are shown in Table 1-2. Samples for determining color characteristics were made from ingots by pressure treatment and heat treatment with final rolling in polished rolls.

The resulting alloy had the following composition, wt.%: Gold - 72, platinum - 5, silver - 11, copper - 11, zinc - 0.9, iridium - 0.1 (this alloy is indicated in the tables below as "LB"). The ratio of the components of the claimed alloy to obtain the specified technical result is as follows: (Au + Pt + Ir) = 77.1, the ratio of silver to copper Ag / Cu = 1, the ratio of silver to platinum Ag / Pt = 2.2, the ratio of platinum and silver to base elements (Ag + Pt) / (Cu + Zn) = 1.34.

Table 1 presents data on color, mechanical properties, and corrosion resistance. Legend:

Evil is pure gold

2, 7, 9, 11, 12, 13 - No. of alloys of the closest analogue (compositions in Table 1 [2]).

LB - claimed alloy

Table 1 No. of alloys The total content of gold and platinoids,% Mechanical properties CIE L a b color specifications Yellowness Index YI according to ASTM E 313-00 Corrosion resistance Yield strength H / mm ² Relative elongation,%% Hardness hv L a * b * The maximum value of the density of the anode current, μA / cm ² otzh strengthened otzh strengthened otzh strengthened 2 71,99 - - - - - - - - - - 6.4 7 74.29 360 585 thirty twenty 155 230 82.0 3,7 19.6 - - 9 97.00 - - - - 195 - - 13.5 - - 10 85.09 - - - - - - 12.0 - - eleven 66.70 - - - - 300 - - - - fourteen 12 74.8 - - - - 12.9 - - 13 75.59 - - - - 230 - - 18,4 - - LB 77.1 300-390 455-620 16-42 9-19 155-160 220-225 74.05 4.75 15.17 27.27 5.2 Evil 99,99 - - - - - - 85.93 8.35 37.7 50.00 -

The resulting alloy "LB" and analog alloys No. 7 and 3 have a pronounced yellow color in contrast to the pale yellow alloys No. 9, 10, and 12.

The yellowness coefficient YI of the obtained LB alloy is 27.27, i.e. higher than 24 for pale yellow alloys and significantly higher than 20 for which the alloys look almost white (with a faint yellow hue).

Electrochemical studies were carried out in a solution of artificial saliva (0.4 g / l KCl, 0.4 g / l NaCl, 0.795 g / l CaCl ₂ · H ₂ O, 0.69 g / l Na ₂ HPO ₄ · H ₂ O, 0.005 g / l Na ₂ S · 9H ₂ O, 1 g / l urea, the rest is water), pH 5.8.

The corrosion resistance of the studied alloys was compared by the height of the peaks of the anode current in the current – voltage curves. As can be seen in Table 1, the LB alloy containing Au + platinoids> 75% has the best corrosion properties in a solution of artificial saliva.

Thus, it can be seen from the obtained data that the proposed alloy has a number of advantages compared with the alloy of the closest analogue. The proposed alloy has a yellowness coefficient of more than 24, an optimal combination of mechanical properties (high yield strengths that meet the requirements of the standard, combined with a sufficiently high ductility), which ensures the reliability of the dental structure, high corrosion resistance.

Claims (1)

An alloy for dentistry based on gold, containing silver, platinum, copper, zinc and iridium, characterized in that it contains components in the following amount, wt.%: Silver 10-12 Platinum 4-5 Copper 10-12 Zinc 0.6-1.0 Iridium 0.05-0.15 Gold Rest, subject to the following conditions: (Au + Pt + Ir) ≥75 wt.%; Ag / Cu = 0.9 ÷ 1.1; Ag / Pt = 2.0 ÷ 2.4; (Ag + Pt) / (Cu + Zn) = 1.2 ÷ 1.4, and has a yellowness coefficient YI of more than 24.