  Structured light mechanically interacts with matter via optical forces and
torques. The optical torque is traditionally calculated via the flux of total
angular momentum (AM) into a volume enclosing an object. In [Phys. Rev. A 92,
043843 (2015)] a powerful method was suggested to calculate optical torque
separately from the flux of the spin and the orbital parts of optical AM,
providing useful physical insight. However, the method predicted a new type of
dipolar torque dependent on the gradient of the helicity density of the optical
beam, inconsistent with prior torque calculations. In this work we intend to
clarify this discrepancy and clear up the confusion. We re-derive, from first
principles and with detailed derivations, both the traditional dipolar total
torque using total AM flux, and the spin and orbital torque components based on
the corresponding AM contributions, ensuring that their sum agrees with the
total torque. We also test our derived analytical expressions against numerical
integration, with exact agreement. We find that `helicity gradient' torque
terms indeed exist in the spin and orbital components separately, but we
present corrected prefactors, such that upon adding them, they cancel out, and
the `helicity gradient' term vanishes from the total dipolar torque,
reconciling literature results. We also derive the analytical expression of the
quadrupolar torque, showing that it is proportional to the spin of the EM field
gradient, rather than the local EM field spin, as sometimes wrongly assumed in
the literature. We provide examples of counter-intuitive situations where the
spin of the EM field gradient behaves very differently to the local EM spin.
Naively using the local EM field spin leads to wrong predictions of the torque
on large particles with strong contributions of quadrupole and higher-order
multipoles, especially in a structured incident field.
