In cast alloys, contact with gingival tissues is primarily due to which substance?

• A. metal ions
• B. ceramic particles
• C. water
• D. resin

Answer: (A)

The main idea is that gingival contact from cast alloys comes from metal ions released when the alloy corrodes or wears in the mouth. In the oral environment, saliva, pH changes, and occasional galvanic currents can disrupt the protective oxide layer on the metal, causing ions such as nickel, chromium, cobalt, copper, and others to leach into the surrounding tissues. Those ions can irritate gingival tissues and, in some people, trigger hypersensitivity reactions. Water is just the medium that carries these ions, not the primary source of tissue contact, while resin and ceramic particles are not the typical constituents released from metal casting alloys. So, the substance primarily responsible for gingival contact is metal ions released from the alloy.