  We combined hydrodynamical simulations of planet-disk interactions with dust
evolution models that include coagulation and fragmentation of dust grains over
a large range of radii and derived observational properties using radiative
transfer calculations. We studied the role of the snow line in the survival of
the inner disk of transition disks. Inside the snow line, the lack of ice
mantles in dust particles decreases the sticking efficiency between grains. As
a consequence, particles fragment at lower collision velocities than in regions
beyond the snow line. This effect allows small particles to be maintained for
up to a few Myrs within the first astronomical unit. These particles are
closely coupled to the gas and do not drift significantly with respect to the
gas. For lower mass planets (1$M_{\rm{Jup}}$), the pre-transition appearance
can be maintained even longer because dust still trickles through the gap
created by the planet, moves invisibly and quickly in the form of relatively
large grains through the gap, and becomes visible again as it fragments and
gets slowed down inside of the snow line. The global study of dust evolution of
a disk with an embedded planet, including the changes of the dust aerodynamics
near the snow line, can explain the concentration of millimetre-sized particles
in the outer disk and the survival of the dust in the inner disk if a large
dust trap is present in the outer disk. This behaviour solves the conundrum of
the combination of both near-infrared excess and ring-like millimetre emission
observed in several transition disks.
