  We study topological properties of density wave states with broken
translational symmetry in two-dimensional multi-orbital systems with a
particular focus on t$_{2g}$ orbitals in square lattice. Due to distinct
symmetry properties of d-orbitals, a nodal charge or spin density wave state
with Dirac points protected by lattice symmetries can be achieved. When an
additional order parameter with opposite reflection symmetry is introduced to a
nodal density wave state, the system can be fully gapped leading to a band
insulator. Among those, topological density wave (TDW) insulators can be
realized, when an effective staggered on-site potential generates a gap to a
pair of Dirac points connected by the inversion symmetry which have the same
topological winding numbers. We also present a mean-field phase diagram for
various density wave states, and discuss experimental implications of our
results.
