Which metal commonly used in implants is not in stainless steel?

• A. Cobalt
• B. Nickel
• C. Titanium
• D. Chromium

Answer: (C)

Titanium is the metal commonly used in implants that is not part of stainless steel alloys. Stainless steel is an iron-based alloy that relies on chromium (and often nickel or molybdenum) to resist corrosion. Titanium, by contrast, is a separate metal with a very stable protective oxide layer, excellent biocompatibility, and a high strength-to-weight ratio. These properties make titanium especially well suited for long-term implants such as orthopedic and dental devices, and it’s not included as a constituent in stainless steel. The other metals listed are elements you’ll find in stainless steel or in other implant alloys (chromium and nickel are common stainless-steel components, while cobalt-chromium alloys are another implant option), but titanium does not appear in stainless steel.