Polymerisationsschrumpfung neuer Komposit-Füllungswerkstoffe

The risk for gap formation in composite restorations is determined by the shrink age due to polymerisation, the viscous flow and creep of the filling material and its adhesion to the cavity wall. These properties and their variations with time during the polymerisation process act together by creating and reducing stresses in the filling in a very complex way. Probably the most important influence is given by the shrinking behaviour. Therefore, as a first step, the goal of this study was to get more information on the time dependence of the polymerisation shrinkage of several newer polymer based filling materials. Eleven filling materials, among them four so-called condensable versions, were investigated. The shrinkage in volume was measured from the beginning of polymerisation until 1 hour thereof when the main polymerisation processes are complete. For this purpose a buoyancy method was applied. These composites show differences in the total shrinkage between 1.7 and 3 vol%. This means an improvement compared to earlier investigated materials.