The sealing capacity of intermediary base materials

P ermanent filling materials have some deficiencies such as dehydration of dentin by the withdrawal of water during the hardening process, penetration of pulpirritating components of the filling material into dentin, and microleakage around the filling due to lack of adaptation. To protect the pulp against these irritations, an applied intermediary base material that has good sealing properties should be used. Intermediary base materials can be divided into three groups: varnishes, liners (varnish with additives such as calcium hydroxide or zinc oxide), and cements. In vitro the amount of most varnishes applied as a continuous layer has slight permeability.‘” However, in vivo experiments suggest that these varnishes are not always as effective as pulp protectors as might be expected from the results of the in vitro experiments.‘-” This discrepancy may occur because in most in vitro experiments the investigated materials are applied on materials different from dentin. For testing the sealing capacity of varnishes, the kind of supporting material is important. A supporting material with bad wetting properties may lead to discontinuities in the obtained layers.* This investigation studied the sealing properties of some intermediary base materials applied in vitro on dentin in a way that corresponds as much as possible with the in vivo situation in dental practice.