Dental Materials. SOLDERING STAINLESS STEEL Current Notes No. 44

38 Australian Dental Journal, February, I960 Dental Materials SOLDERING STAINLESS STEEL Current Notes No. 44* The problem of soldering stainless steel in dentistry, particularly in orthodontics, differs from that of soldering precious metals in several important respects. Providing that the correct materials are used and a satisfactory technique is employed failures should be rare. Materials 1. The stainless steel.-A specification for stainless steel wire is being prepared through the Standards Association of Australia. 2. The solder.-The solder should comply with the current specification of the Standards Association of Australia. A tentative draft was drawn up i n January, 1957. (Industrial solders are not generally suitable for use in the human mouth.) 3. The flux.-The most satisfactory flux for soldering stainless steel for dental purposes found so far consists of: Acid potassium fluoride (KHF‘,) - Boracic acid 3 parts by weight 2 parts by weight The flux should be acid and it should contain acid potassium fluoride. It should not contain borax. The melting temperature of the flux should be lower than that of the solder with which it is used. Industrial fluxes are not generally suitable for dental purposes. Technique 1. The burner.-The most satisfactory burner that has been found so far is a n 18 gauge hypodermic needle used with ordinary coal gas. A stand or clamp to support the needle is helpful. *Prepared by Dr. J. Wunderly in associa- tion with the Commonwealth Bureau of Dental Standards. The flame issuing from the needle can be adjusted to lengths from 4“ to about 2”. A length up to about 5’’ is suitable for the majority of orthodontic soldered joints. As the aim should be to use the minimum effective heat in soldering stainless steel for dental purposes, a n air-gas flame of any type is contra-indicated. 2. The method.-Silver solder does not alloy with stainless steel and therefore its hold is only mechanical. If two pieces of stainless steel wire are to be united by a soldered joint, fine grooves should be made with a fine file o r a penknife near their ends. The solder will flow into the grooves and strengthen the hold of the solder on the wires. When soldering a stainless steel band, it is not necessary to notch or groove the band material. Grooving is not required when a bracket or a buccal tube is being soldered to a stainless steel band. It is important to use more flux and more solder for stainless steel than for precious metals. A liberal amount of flux is needed in all soldering of stainless steel, and fluxing should always precede the introduction of the solder to form the union. The flux is easy to manipulate if moistened with water. Some flux, about the size of a match head, should be melted on to the end of each piece of wire. Some solder, preferably in the form of wire, is then melted into the flux on each piece of wire. The two masses of solder are then joined by heat. The flux should then be removed by scraping and washing under water. Industrial fluxes and solders are obtainable on the market and are sometimes supplied for dental purposes. This might save a penny per patient, but their use on any article that is to be worn in the mouth is considered risky.