The purpose of this paper is to investigate the influence of interphase properties on restored-tooth structure due to polymerization shrinkage of resin-based composite. The stress within the restored tooth structure built up from the polymerization shrinkage of the restorative composite was computed accounting for the time-dependent and viscoelastic behavior of the composite. A sensitivity study was performed to examine the relative influence of geometric and material parameters of an interphase on the shrinkage stress development. It was found that a correlation exists between material and geometry properties at the restoration-tooth interface and higher shrinkage stresses were located at the interphase due to polymerization shrinkage. The varying material and geometry properties of restoration-tooth interface seemed to have a conclusive effect on the interfacial stress system, as well as on the longevity of the restoration.