The elastic limit of nickel-containing and nickel-free cobalt-chromium circumferential clasp arms.

The purpose of this study was to compare the flexibility and rigidity of the retentive arms of cast circumferential clasps prepared from two nickel-containing alloys (Vitallium and Wironit) with a nickel-free alloy (Biosil). Standardised wax patterns were adapted to 30 specially prepared refractory casts. Ten of these waxed casts were sent to each of three commercial laboratories that specialize in making castings from each of the alloys to be tested.