Marginal sealing of curing contraction gaps in Class V composite resin restorations.

When one uses composite resins, the curing contraction, the stiffness of the material, and the strength of the vulnerable dentinal bond are important factors in determining the marginal adaptation of the restoration. Calculations based on these intrinsic material properties have indicated that both bulk placement and incremental placement of the restorative material in the cervical cavity inevitably lead to marginal gap formation. Sealing of this gap with an unfilled low-viscosity resin, directly after the composite resin is cured, may lead to perfectly closed restoration margins, provided that composites with low linear curing contraction and low Young's modulus are used. These conditions were experimentally shown to be valid for laboratory and clinical situations.