Describe the problems that occur when soldering gold to cobalt chrome. Describe methods by which these problems may be overcome / avoided.

Describe the problems that occur when soldering gold to cobalt chrome. Describe methods by which these problems may be overcome / avoided.

1. To join cast dental alloys by soldering, a “third” low fusing alloy (solder) is required. The melting range of this solder must be lower than the melting range of the alloys; otherwise the metalwork you are joining would be deformed or melted by the torch during the soldering procedure.

2. To decrease the melting range of the solder, low fusing elements such as cadmium, gallium, nickel and copper are mixed into the soldering alloy.

   • These elements, however, have a questionable corrosion resistance and in many cases will constantly dissolve in the oral environment. The dissolved metal ions settle in organs (kidney, liver, etc.), leading to allergic reactions (i.e. nickel) and other health problems for the patient.

3. Specific fluxes and solders need to be used for the alloys being joined. Care has to be taken regarding the temperature of the metals being soldered and also whether any of the metal to be joined is covered in acrylic. The use of heat barrier creams is advised in the latter situation.

4. Small investment blocks are generally used to maintain position of components. The use of a small furnace is also recommended to ensure finite temperature control during the soldering procedure.