  The canonical understanding of quantum oscillation in metals is challenged by
the observation of de Haas-van Alphen effect in an insulator, SmB$_{6}$ [Tan
\emph{et al}, Science {\bf349}, 287 (2015)]. Based on a two-band model with
inverted band structure, we show that the periodically narrowing hybridization
gap in magnetic fields can induce the oscillation of low-energy density of
states in the bulk, which is observable provided that the hybridization gap is
narrow and comparable to the Landau level spacing. Its temperature dependence
strongly deviates from the Lifshitz-Kosevich theory. The nontrivial band
topology manifests itself as a nonzero Berry phase in the oscillation pattern,
which crosses over to a trivial Berry phase by increasing the temperature or
the magnetic field. Further predictions to experiments are also proposed.
