In cast alloys, which component contacts gingival and mucosal tissues?

• A. Resin monomers
• B. Metal ions
• C. Water
• D. Ceramic fragments

Answer: (B)

In cast dental alloys, the main biocompatibility concern is the release of metal ions from the alloy into the oral environment. The metal framework sits next to gingival and mucosal tissues, and saliva can promote corrosion or wear of the alloy, releasing ions such as nickel, chromium, cobalt, and others. These ions can then contact the soft tissues directly, potentially causing irritation, hypersensitivity reactions, or cytotoxic effects if the patient is sensitive or if ion levels are high. This is why biocompatibility assessments for cast alloys focus on ion release and the resulting tissue responses.

Resin monomers pertain to resin-based materials rather than metal casting, so they aren’t the component in contact with tissues for a cast alloy. Water serves as a medium that facilitates ion movement but isn’t the material itself contacting the tissues. Ceramic fragments would only be relevant if there were porcelain components involved, which isn’t the metal casting context.