  We study the effects of pion and sigma meson backcoupling on the chiral order
parameters and the QCD phase diagram and determine their effect on the location
of the chiral critical endpoint. To this end, we solve a coupled set of
truncated Dyson--Schwinger equations for Landau gauge quark and gluon
propagators with $N_f=2+1$ dynamical quark flavors and explicitly backcoupled
mesons. The corresponding meson bound-state properties and the quark-meson
Bethe--Salpeter vertices are obtained from their homogeneous Bethe--Salpeter
equation. We find chiral-restoration effects of the pion and/or sigma meson
backcoupling and observe a (small) shift of the critical endpoint towards
smaller chemical potentials. The curvature of the chiral crossover line
decreases. Our results indicate that the location of the critical endpoint in
the phase diagram is mainly determined by the microscopic degrees of freedom of
QCD (in contrast to its critical properties).
