The strength of multilayer and repaired composite resin

Composite resin surfaces that formed against a plastic matrix or that polymerized while exposed to air were excellent substrates for the adhesion of new resin. Samples formed by the addition of composite resin to a cut surface had a tensile strength of one half of the cohesive strength of the resin. Coating the cut surface with a thin layer of unfilled resin enhanced bonding of the second composite resin layer. The use of a thin layer of unfilled catalyst resin as a bonding agent caused the most rapid development of strength and the greatest strength in samples tested after 7 days.