【発明の詳細な説明】[Detailed description of the invention]
本発明は歯科補綴物を鋳造によつて造る時に使
用する銀合金に関するものである。
歯科においては補綴物を製作する際には金合
金、金銀パラジウム合金、銀合金など各種の合金
が使用されているが、物性、操作性、口腔内の耐
蝕性の点で金合金が最も賞用されている。
しかしながら近年貴金属の急激な高騰によつて
金を全く含有しないものか、或いは含んでいると
しても極めて少量で金合金に匹敵する優れた性能
を有する合金の開発が強く要望されている。
歯科補綴物としてはインレー、クラウン、ブリ
ツジ、バー、床など各種あり、之等が口腔内で
夫々の役割を果たすためには所求の物理的性質の
他に口腔内における耐蝕性が極めて重要である。
銀合金においてパラジウムの含有量を増加させ
ると銀の耐蝕性及び耐硫化性などを著しく改善す
る効果があることが知られている。しかし一面で
はパラジウムはガスを吸蔵し易い性質を有してい
るので鋳巣発生という欠陥を持つた鋳造体が出来
易い。
本発明者等はパラジウムと銀とを基礎成分と
し、しかもガス吸蔵が無く、溶融点が低く、溶湯
の湯流れが良く、硬さと引張強さの向上した鋳造
欠陥の少ない合金を創出することを目的として研
究を重ねた結果、微量の活性元素の使用によつて
物性並びに耐蝕性に優れた新しいパラジウム銀合
金を作製することに成功した。
以下、本発明の構成と数値限定を行なつた根拠
について詳述する。
本発明の銀合金は銀の耐硫化性及び耐酸性を付
与するのに最も効果的なパラジウムを利用するも
のではあるが、パラジウムの含有量を15〜30重量
％と規定した。即ちJIS T6106“歯科鋳造用金銀
パラジウム合金の変色試験”における規定限界を
維持するために最低量15重量％のパラジウムが必
要であるので下限をパラジウム15重量％と規定し
た。更にパラジウムを30重量％を超えて配合する
とパラジウムの溶融点が1554℃であるので合金の
溶融点が上昇し通常の歯科鋳造で使用されている
都市ガスやプロパンガスと空気との混合炎では溶
融困難となるため、パラジウムの含有上限を30重
量％と規定した。
また銅は合金の熱処理硬化性付与に重要な成分
であり、パラジウムと共にPdCu3，PdCu相の析
出によつて合金に強度と弾性とを付与することが
出来るが、10重量％未満の銅含有量では銅添加の
効果が充分発揮されず、また20重量％を超えると
合金の耐蝕性を劣化させる恐れがある。更に合金
を繰返し溶融した場合に酸化物を生成し鋳造性を
著しく阻害するので20重量％を上限とした。
ゲルマニウムは銀、パラジウム、白金などの加
熱または溶融時にガス吸蔵を極度に抑制する性質
を有している。更にゲルマニウムは脱酸剤として
効果的であつて鋳造性の改善に寄与する特性を有
している。それらの効果を有効に発揮出来る有効
量は１重量％以上であり、５重量％を超えて添加
した場合には却つて合金の伸びを著しく害し、加
工性を不良ならしめ作業を困難とするのでゲルマ
ニウムの有効範囲を１〜５重量％と規定した。
亜鉛は脱酸剤として用いるのであるが、ゲルマ
ニウムで代用することが出来るが、亜鉛0.3重量
％以上をゲルマニウムと共存させると脱酸効果が
相乗される。しかし亜鉛が0.3重量％未満ではそ
の効果が少なく、３重量％を超えて含有されると
合金の硬さが過大となり脆弱化となるので0.3〜
３重量％と規定した。
インジウムは溶融点を下げ、鋳造性を改善する
し熱処理効果を助長させ硬化熱処理後の硬さと引
張強さを増加させるが、１重量％未満ではその効
果が少なく、３重量％を超えると合金を脆弱化さ
せるので添加量を１〜３重量％と規定した。
以下に実施例を挙げて本発明の効果を更に説明
する。
次に示す表１はパラジウム、銅、ゲルマニウ
ム、銀に更にインジウム、亜鉛を含ましめた実施
例を示す。
The present invention relates to a silver alloy used when manufacturing dental prostheses by casting. In dentistry, various alloys such as gold alloys, gold-silver-palladium alloys, and silver alloys are used to manufacture prosthetics, but gold alloys are the most prized in terms of physical properties, operability, and intraoral corrosion resistance. has been done. However, due to the rapid rise in the price of precious metals in recent years, there has been a strong demand for the development of alloys that do not contain gold at all, or even if they do, contain only a very small amount of gold and have excellent performance comparable to gold alloys. There are various types of dental prostheses such as inlays, crowns, bridges, bars, and floors, and in order for these to play their respective roles in the oral cavity, in addition to the required physical properties, corrosion resistance in the oral cavity is extremely important. be. It is known that increasing the palladium content in a silver alloy has the effect of significantly improving the corrosion resistance and sulfidation resistance of silver. However, on the one hand, palladium has the property of easily occluding gas, so it is easy to produce cast bodies with defects such as the formation of cavities. The present inventors have aimed to create an alloy that has palladium and silver as basic components, has no gas storage, has a low melting point, has good flow of molten metal, has improved hardness and tensile strength, and has fewer casting defects. As a result of repeated research aimed at this purpose, we succeeded in creating a new palladium-silver alloy with excellent physical properties and corrosion resistance by using trace amounts of active elements. Hereinafter, the configuration of the present invention and the basis for limiting the numerical values will be explained in detail. Although the silver alloy of the present invention utilizes palladium, which is most effective in imparting sulfidation resistance and acid resistance to silver, the content of palladium is specified to be 15 to 30% by weight. That is, since a minimum amount of palladium of 15% by weight is required to maintain the specified limit in JIS T6106 "Discoloration test of gold-silver-palladium alloy for dental casting", the lower limit was defined as 15% by weight of palladium. Furthermore, if more than 30% by weight of palladium is added, the melting point of palladium is 1554°C, so the melting point of the alloy will rise and it will not melt in the mixed flame of city gas or propane gas and air used in normal dental casting. Since this would be difficult, the upper limit of palladium content was set at 30% by weight. Copper is also an important component for imparting heat treatment hardenability to alloys, and together with palladium, it can impart strength and elasticity to alloys through the precipitation of PdCu 3 and PdCu phases, but copper content of less than 10% by weight If the copper content exceeds 20% by weight, the corrosion resistance of the alloy may deteriorate. Furthermore, when the alloy is repeatedly melted, oxides are generated, which significantly impedes castability, so the upper limit was set at 20% by weight. Germanium has the property of extremely suppressing gas absorption when silver, palladium, platinum, etc. are heated or melted. Furthermore, germanium is effective as a deoxidizing agent and has properties that contribute to improving castability. The effective amount that can effectively exhibit these effects is 1% by weight or more, and if added in excess of 5% by weight, it will significantly impair the elongation of the alloy, impairing workability and making work difficult. The effective range of germanium was defined as 1 to 5% by weight. Zinc is used as a deoxidizing agent, and germanium can be substituted, but when 0.3% by weight or more of zinc coexists with germanium, the deoxidizing effect is synergized. However, if the zinc content is less than 0.3% by weight, the effect will be small, and if the content exceeds 3% by weight, the hardness of the alloy will be excessive and it will become brittle.
It was defined as 3% by weight. Indium lowers the melting point, improves castability, promotes the heat treatment effect, and increases the hardness and tensile strength after hardening heat treatment, but if it is less than 1% by weight, the effect is small, and if it exceeds 3% by weight, it will deteriorate the alloy. Since it causes brittleness, the amount added is specified to be 1 to 3% by weight. The effects of the present invention will be further explained below with reference to Examples. Table 1 below shows examples in which indium and zinc were further included in addition to palladium, copper, germanium, and silver.
【表】
表１に示した実施例の合金を製作した後、溶融
点の測定はタンマン管に合金試料を入れ電気加熱
装置で溶融し熱電温度計を使用し放冷の際におけ
る温度変化を自動記録計で読取り溶融点（固相
点）を表示した。
また変色試験は硫化ソーダ0.1％溶液中へ浸漬
し３日間37℃に保持する方法即ちJIS T6105に準
じて行なつた。
引張強さ及び伸びの測定は直径２mmφ、平行部
の長さ30mmの丸棒を歯科鋳造方法に準じて鋳造し
試験片を作製した後、その試料を700℃炉中で10
分間加熱後、水中へ急冷する軟化処理と、軟化処
理後、更に450℃炉で20分間加熱後、空冷する硬
化熱処理調整したものを引張速度0.5mm／分で引
張り、その最大抗張力と標点間距離20mmでの伸び
を求めた。引張強さは測定値のバラツキを統計計
算による95％信頼区間値を算出し平均値に付与し
表示した。
硬さは10×15×1.5mmの試験片を歯科鋳造方法
に準じて鋳造し、軟化・硬化熱処理後ビツカース
硬度計を使用し荷重１Kgで測定した。
溶融点は実施例では1000℃以下で一般歯科鋳造
法の都市ガスまたはプロパンガスと空気の混合炎
で容易に溶融が出来、鋳造が可能であつた。特に
この操作で実施例合金は溶融時に酸化されること
なく奇麗な鏡面を呈し、鋳込みのタイミングを適
確に把握することが出来る。
変色試験では実施例１はJIS T6105の限定範囲
内で、比較例の金銀パラジウム合金市販品例に比
しても同等或いはそれ以上の耐色性で口腔内での
耐色性を証明出来る。
引張強さは表１で明らかな様に本発明合金は軟
化処理で40〜60Kg／mm2、硬化処理で63〜81Kg／mm2
と夫々熱処理硬化を有している。測定値の95％信
頼区間値、即ちバラツキは実施例合金は非常に小
さく、比較例に比し鋳造物で得られる物性は明ら
かに安定で、その有意性が認められる。
引張試験体の破断面を調べた処、本発明合金の
場合は内部欠陥は認められなかつたが、比較例合
金の場合はガス吸蔵と認められる大きな欠陥があ
つた。之等の点が引張強さの95％信頼区間値の大
きさの要因となつている。従つて実施例はガスの
吸蔵を抑制されていることが判る。
また、実施例合金はインジウムを含まない比較
例合金と比較して、インジウムを加えた効果によ
り溶融点が降下し、溶湯の湯流れが容易となり、
細部にわたる鋳造再現性が向上し、且つ物性にお
いては硬さと引張強さが向上し、特に硬化熱処理
により硬さの顕著な向上が認められた。
以上、本発明の銀、パラジウム、銅、ゲルマニ
ウム、インジウム、亜鉛などの金属を組み合わせ
て製作した銀合金は従来用いられている歯科用金
銀パラジウム合金（比較例Ｂ）に匹敵する強度、
物性を有していて、また本発明合金は耐変色性に
優れているだけでなく更に低価格で供給出来、経
済的な合金であり、歯科臨床に寄与する処大なる
ものがある。[Table] After producing the alloys of the examples shown in Table 1, the melting point was measured by placing the alloy sample in a Tammann tube, melting it with an electric heating device, and using a thermocouple to automatically measure the temperature change during cooling. The melting point (solidus point) was read using a recorder. The discoloration test was conducted in accordance with JIS T6105, in which the sample was immersed in a 0.1% sodium sulfide solution and maintained at 37°C for 3 days. To measure tensile strength and elongation, a test piece was prepared by casting a round bar with a diameter of 2 mmφ and a parallel part length of 30 mm according to the dental casting method, and then the sample was heated in a 700℃ furnace for 10
A softening treatment in which the material is heated for 1 minute, then rapidly cooled in water, and then a hardening treatment in which it is further heated in a 450°C furnace for 20 minutes and then air cooled, is stretched at a tensile speed of 0.5 mm/min, and its maximum tensile strength and gauge point distance are adjusted. The elongation was determined at a distance of 20 mm. For tensile strength, a 95% confidence interval value was calculated by statistical calculation based on the dispersion of measured values, and the value was added to the average value and displayed. Hardness was measured by casting a test piece of 10 x 15 x 1.5 mm according to the dental casting method, and after heat treatment for softening and hardening, using a Bitkers hardness tester at a load of 1 kg. In the examples, the melting point was 1000°C or less, and it was easy to melt and cast using a mixed flame of city gas or propane gas and air used in general dental casting methods. In particular, this operation allows the example alloy to exhibit a beautiful mirror surface without being oxidized during melting, making it possible to accurately determine the timing of casting. In the discoloration test, Example 1 was able to prove its color fastness in the oral cavity within the limits of JIS T6105, with a color fastness equal to or better than that of the commercial gold-silver-palladium alloy example of the comparative example. As is clear from Table 1, the tensile strength of the alloy of the present invention is 40 to 60 Kg/mm 2 after softening treatment, and 63 to 81 Kg/mm 2 after hardening treatment.
and heat treatment hardening. The 95% confidence interval value of the measured value, that is, the variation, is very small for the example alloy, and the physical properties obtained in the cast product are clearly stable compared to the comparative example, and its significance is recognized. When the fracture surfaces of the tensile test specimens were examined, no internal defects were observed in the case of the alloy of the present invention, but large defects that were recognized as gas occlusion were observed in the case of the comparative example alloy. These points are factors in the size of the 95% confidence interval value for tensile strength. Therefore, it can be seen that the embodiment suppresses gas occlusion. In addition, compared to the comparative example alloy which does not contain indium, the melting point of the example alloy is lowered due to the effect of adding indium, and the molten metal flows more easily.
Detailed casting reproducibility was improved, and in terms of physical properties, hardness and tensile strength were improved, and in particular, a remarkable improvement in hardness was observed by hardening heat treatment. As mentioned above, the silver alloy produced by combining metals such as silver, palladium, copper, germanium, indium, and zinc of the present invention has strength comparable to that of the conventionally used dental gold-silver-palladium alloy (Comparative Example B).
The alloy of the present invention not only has excellent discoloration resistance but also can be supplied at a low price, making it an economical alloy that greatly contributes to clinical dentistry.