Metallurgy of Stainless Steel and Cobalt – Chromium alloys

orthodontic wire in 1929 and shortly gained popularity over the other orthodontic wires. The term “corrosion-resisting steel” applies to high chromium, high nickel steel used in the construction of orthodontic appliances. At present it is used widely in the industrial field, and as it is based on a standard of 18 per cent chromium, 8 per cent nickel, it is known as an austenitic alloy and recognized by the term 18-8. With its varied uses stainless steel has now become an integral part of orthodontic profession today.

Chrome cobalt alloys were simultaneously developed in the mid century and this had physical properties very similar to that of stainless steel. However they had the advantage that they could be supplied in softer and more form-able state and then could be hardened by heat treatment, the procedure increases its strength significantly.



It is the technology or process of extraction of metals in pure state from their ores economically and profitably. It also includes the study about their properties and uses.


Alloy is a metallic intimately mixed solid mixture of two or more different elements one of which is at least essentially a metal.


Different methods used to prepare alloys are


(1)         Fusion method

(2)         Electro deposition

(3)         Reduction method

(4)         Powder metallurgy or compression method




  1. The alloys chemical nature should not produce harmful toxic or allergenic effects in the patient or the operator.
  2. The chemical properties of the appliances should provide resistance to corrosion and physical changes when in the oral fluids.
  3. The physical and mechanical properties such as strength, modulus of elasticity, coefficient of thermal expansion, conductivity should all be satisfactory.
  4. The technical expertise needed for fabrication and use should be feasible for the average dentist and skilled technician.
  5. The metals, alloys and companion materials for fabrication should be plentiful, relatively inexpensive and readily available even in periods of emergency.