Which arm in a removable partial denture design has a terminal tip that extends below the survey line into the undercut?

Which arm in a removable partial denture design has a terminal tip that extends below the survey line into the undercut?

• A. Reciprocating / bracing arm
• B. Wrought wire
• C. Indirect retainer
• D. Retentive clasp arm

Answer: (D)

In removable partial denture design, retention comes from engaging undercuts on the abutment teeth, which is determined by the survey line. The arm that provides retention is the retentive clasp arm. Its terminal tip is formed to extend below the survey line into the undercut so it can seat into that undercut and resist dislodgement when forces try to lift the denture. The other arms have different roles: the reciprocating/bracing arm stabilizes against movement but does not rely on extending into an undercut below the survey line; indirect retainers use rests to resist vertical displacement rather than engaging an abutment undercut; wrought wire clasps are a fabrication option but don’t define the retention mechanism described by the terminal tip extending into the undercut.

In removable partial denture design, retention comes from engaging undercuts on the abutment teeth, which is determined by the survey line. The arm that provides retention is the retentive clasp arm. Its terminal tip is formed to extend below the survey line into the undercut so it can seat into that undercut and resist dislodgement when forces try to lift the denture. The other arms have different roles: the reciprocating/bracing arm stabilizes against movement but does not rely on extending into an undercut below the survey line; indirect retainers use rests to resist vertical displacement rather than engaging an abutment undercut; wrought wire clasps are a fabrication option but don’t define the retention mechanism described by the terminal tip extending into the undercut.