  Motivated by intertwined crystal symmetries and topological phases, we study
the possible realization of topological insulator in nonsymmorphic crystals at
integer fillings. In particular, we consider spin orbit coupled electronic
systems of two-dimensional crystal Shastry-Sutherland lattice at integer
filling where the gapless line degeneracy is protected by glide reflection
symmetry. Based on a simple tight-binding model, we investigate how the
topological insulating phase is stabilized by breaking nonsymmorphic symmetries
but in the presence of time reversal symmetry and inversion symmetry. In
addition, we also discuss the regime where Dirac semimetal is stabilized,
having non trivial $Z_2$ invariants even without spin orbit coupling (SOC). Our
study can be extended to more general cases where all lattice symmetries are
broken and we also discuss possible application to topological Kondo insulators
in nonsymmorphic crystals where crystal symmetries can be spontaneously broken
as a function of Kondo coupling.
