【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、引張強さが大きく鋳
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。
亜鉛を１重量％以上加えることにより以下に示
す実施例によつて明らかな如く合金の引張強度が
増大する。ま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も出来るがゲ
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５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となるので１〜５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は本発明の基本成分たるパラジウ
ム、銅、ゲルマニウム、銀に亜鉛を含ませた実施
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. As a result of repeated research aimed at creating an alloy that uses palladium and silver as basic components, has no gas storage, has high tensile strength, and has few casting defects, the present inventors have found that the use of a trace amount of active elements has been achieved. As a result, we succeeded in producing a new palladium-silver alloy with excellent physical properties and corrosion resistance. 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 palladium exceeds 30% by weight, the melting point of palladium is 1554°C, so the melting point of the alloy will rise, making it difficult to melt with the mixed flame of city gas or propane gas and air used in normal dental casting. Therefore, 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. Adding more than 1% by weight of zinc increases the tensile strength of the alloy as evidenced by the examples below. Zinc is used as a deoxidizing agent, and germanium can also be substituted, but the deoxidizing effect is synergized when it coexists with germanium. However, if zinc is contained in an amount exceeding 5% by weight, the alloy becomes too hard and brittle, so it is specified as 1 to 5% by weight. The effects of the present invention will be further explained below with reference to Examples. Table 1 shown below shows examples in which zinc is included in palladium, copper, germanium, and silver, which are the basic components of the present invention.
【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。
引張強さの測定は直径２mmφ、平行部の長さ30
mm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
の最大抗張力を求めた。その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。
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はJIS T6105の限定範囲内
で、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。また実施例合金
は、測定値の95％信頼区間値、即ちバラツキがゲ
ルマニウムを含まない比較例合金と比較して非常
に小さく、且つ引張強さが亜鉛を含まない比較例
合金と比較して高い値を示しており、ゲルマニウ
ムと亜鉛が共存することによつて脱酸効果が相乗
されていることが認められ、比較例合金に比べ鋳
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。
以上、本発明の銀、パラジウム、銅、ゲルマニ
ウムを基本組成となし、更に亜鉛を組み合わせて
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）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. The tensile strength is measured with a diameter of 2 mmφ and a parallel part length of 30 mm.
After making a test piece by casting a mm round bar according to the dental casting method, the sample was heated in a 700℃ furnace for 10 minutes, then rapidly cooled in water, and after the softening treatment, it was further heated in a 450℃ furnace. After heating for 20 minutes, the hardening heat treated material was air cooled and pulled at a tensile speed of 0.5 mm/min to determine its maximum tensile strength. A 95% confidence interval value was calculated by statistical calculation for the dispersion of the measured values, and the value was added to the average value and displayed. 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, the Examples were able to prove the color fastness in the oral cavity, which was within the limits of JIS T6105, and was equivalent to or better than commercial examples of gold-silver-palladium alloys. 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. In addition, the example alloy has a 95% confidence interval value of the measured value, that is, a very small variation compared to the comparative example alloy that does not contain germanium, and a higher tensile strength than the comparative example alloy that does not contain zinc. It is recognized that the deoxidizing effect is synergistic due to the coexistence of germanium and zinc, and the physical properties obtained in the cast product are clearly stable compared to the comparative example alloy, and its significance is clear. 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. As mentioned above, the silver alloy of the present invention, which has a basic composition of silver, palladium, copper, and germanium, and which is produced in combination with zinc, has strength and physical properties comparable to conventional dental gold-silver-palladium alloys (comparative example). In addition, 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.