Bond strength of photocured composite resin facings: clinical versus laboratory procedures

The tensile strengths of laboratory versus clinical photocured composite resins have been investigated. Metal surfaces were bonded to photocured composite resin by either retentive beads, Sebond or Silicoating. The bond strengths were measured by an Instron machine and the fracture sites observed. Following repair with the adhesives Dentacolor Opaquer, Fusion and Cover up 2, the Instron measurements were repeated. The metal/facing bond strength was the highest in samples fabricated by the Silicoating technique, the bond strength exceeding the cohesive forces in the composite resin facing. The tensile strengths of metal/facing bonded by Sebond and retentive beads were similar. Fractures that include the facing and partially reveal the metal are the least resistant to tension after repair. Renewal of the Opaque layer and completion of the facing is superior to any of the repair methods used in this paper. The original fracture point is the weakest after repair. All the repair kits tested were inferior to the original restoration materials.