By making use of dewetting, the flow of polystyrene ( PS) in confined geometry of ultrathin films is investigated as a function of the boundary conditions. Four different surface treatment procedures have been applied to silicon ( Si) substrates to realize small changes of the oxide surfaces. Atomic force microscopy and surface-sensitive scattering experiments show a change in the mass transport of PS. A slowing down in comparison to the well-known slip and no-slip conditions is observed, except in the case of binodal dewetting mechanisms, which obeys a partial slippage. In addition to the changed kinetic behavior, the final states show big differences in the contact angle of the drops. Our results are explained within a model, which includes changes of the short-ranged part of the wall potential due to different oxide layer thicknesses, introduced by the treatment processes.