Which amalgam type produces the best proximal contact in a Class II restoration?

Correct answer: A. Admixed (blended) alloy

• A. CORRECT. ADMIXED alloy blends irregular lathe-cut particles with spherical ones. The irregular particles RESIST condensation, so the force applied by the operator is transmitted LATERALLY against the matrix band, pushing it firmly against the adjacent tooth. That lateral displacement of the band is precisely what generates a tight proximal contact.
• B. Spherical particles offer little resistance and slip past one another, so condensation force is dissipated vertically rather than transmitted to the band. Proximal contacts are correspondingly lighter.
• C. Alloy particle shape has a marked effect on the achievable contact.
• D. Low-copper alloys of any particle shape are obsolete because of gamma-2 formation, whatever their handling characteristics.

Note: If a spherical alloy must be used for a Class II, compensate with a well-contoured sectional matrix and a separation ring to pre-wedge the contact.