  We compute the full non-perturbative ghost and gluon two-point Green
functions by using gauge field configurations with $\nf=2$ and $\nf=2+1+1$
twisted-mass quark flavours. We use simulations with several different light
quark masses, heavy quark masses close to that of the strange and charm quarks,
and lightest pseudoscalar masses ranging from 270 to 510 [MeV]. Quark flavour
effects on both the gluon and the ghost propagators are then investigated in a
wide range of momenta, bridging the deep infrared and intermediate momenta
domain of QCD interactions in the presence of dynamical quarks. The ghost-gluon
vertex is also indirectly probed through a consistency requirement among the
lattice data for the gluon and ghost propagators and the ghost propagator
Schwinger-Dyson equation. The effective full QCD coupling is finally
constructed, and its dependence on the presence of dynamical fermions
scrutinized.
