Dental alloys

Liječnik dentalne medicine u svakodnevnom se radu služi različitim materijalima. Važna su skupina materijala u dentalnoj medicini metali i legure. Rabe se kao gradivni materijali u restaurativnoj i dječjoj dentalnoj medicini, ortodonciji, protetici i kirurgiji, a također se od njih izrađuju i instrumenti te pomoćna radna sredstva. Metali i legure za primjenu u stomatologiji moraju sadržavati određena svojstva, a među najbitnijima su biokompatibilnost, tvrdoća i čvrstoća. Metali kao zasebni elementi ne odgovaraju uvjetima koje traži zahtjevan okoliš usne šupljine (osim titana), stoga se postupkom legiranja dobivaju različite legure. Legure su mješavina metala s nekim drugim metalom ili nemetalom u čvrstoj otopini, sa svrhom dobivanja boljih svojstava, pri čemu prevladavaju metalna svojstva. Leguru čine komponente ili sastojine i po njihovom broju dijele se na binarne, ternarne i višekomponentne. Metali koji pokazuju međusobnu sklonost (afinitet) i u tekućem i u krutom stanju međusobno se potpuno pomiješaju. Kristalizacijom nastaju čvrste otopine ili kristali mješanci. U dentalnoj medicini smiju se koristiti samo homologne legure s kristalima mješancima jer su one korozijski otporne. Kako bi se olakšao izbor i provela optimalna namjena legura, postoji nekoliko sistematizacija koje se najčešće temelje na vrsti i masenom udjelu pojedinih sastojina, najčešće plemenitih metala. Prema udjelu plemenitih metala legure se dijele na plemenite i neplemenite. Plemenite su legure zlata, srebro-paladijeve i paladijeve, dok u neplemenite legure pripadaju nikal-kromove, kobalt-kromove, legure željeza, titanove legure i amalgam.A dentist uses various materials in his everyday work. An important category of materials in dentistry is metals and alloys. They are used as construction materials in restorative and paediatric dentistry, orthodontics, prosthodontics and oral surgery. Furthermore, they are used in making of dental instruments and auxiliary tools. Dental metals and alloys have to have certain characteristics and the most important ones are biocompatibility, hardness and strength. Metals as separate elements do not satisfy the requirements of the demanding oral cavity environment (except for titan), hence the process of alloying which results in various alloys. Alloys are mixtures of a metal and another metal or non-metal in a solid solution with a purpose of acquiring better properties, with an emphasis on metallic properties. According to the components of the alloy, alloys are categorized into binary, ternary or multicomponent alloys. Metals which show mutual affinity in liquid and solid state blend together completely. Products of crystallization are solid solutions. In dentistry, only homogeneous alloys of identical crystals can be used because they are resistant to corosion. There are few systematizations which are usually based on the type and mass fraction of a certain component, most often noble metals. These systematizations make easier to choose the alloy and find its optimal purpose. Based on the mass fraction of the noble metal in the alloy, alloys can be noble or non-noble. Noble alloys are gold, silver-palladium and palladium alloys and non-noble alloys are nickel-chromium, cobalt-chromium, ferrous and titanium alloys and amalgam