  We investigate the impact of unquenching effects on QCD Green's functions, in
the form of quark-loop contributions to both the gluon propagator and
three-gluon vertex, in a three-loop inspired truncation of the three-particle
irreducible (3PI) effective action. The fully coupled system of Dyson-Schwinger
equations for the quark-gluon-, ghost-gluon- and three-gluon vertices, together
with the quark propagator, are solved self-consistently; our only input are the
ghost and gluon propagators themselves that are constrained by calculations
within Lattice QCD. We find that the two different unquenching effects have
roughly equal, but opposite, impact on the quark-gluon vertex and quark
propagator, with an overall negative impact on the latter. By taking further
derivatives of the 3PI effective action, we construct the corresponding
quark-antiquark kernel of the Bethe-Salpeter equation for mesons. The leading
component is gluon exchange between two fully-dressed quark-gluon vertices,
thus introducing for the first time an obvious scalar-scalar component to the
binding. We gain access to time-like properties of bound-states by analytically
continuing the coupled system of Dyson--Schwinger equations to the complex
plane. We observe that the vector axial-vector splitting is in accord with
experiment and that the lightest quark-antiquark scalar meson is above 1 GeV in
mass.
