From the 2011 UL White Book
..."Preliminary preparation of conductor ? Some wire connectors supply
instructions for the preliminary preparation of conductors, such as use of
conductor termination compound (antioxidant compound) or pre-twisting of
conductors, on or within the unit container.
Pre-twisting ? Some connectors may specify that conductors are to be
pre-twisted before assembly onto the connector.
Conductor termination compound ? Some connectors are shipped prefilled
with conductor termination compound (antioxidant compound). For
non-prefilled connectors, conductor termination compound may be used if
recommended by the connector manufacturer as preliminary preparation of
the conductor. Wire brushing of the conductor may also be performed if recommended.
Also see Conductor Termination Compounds (DVYW)."...
This is out of context but makes the point that others have previuosly stated.
110.14, 110.3(B)