Composite resin support of undermined enamel in amalgam restorations.

PURPOSE Previous reports suggested that cusp fracture strength increases with the use of bonded composites. The purpose of this study was to assess fracture resistance of undermined cusps, when supported by a layer of bonded composite, in extensive occlusal carious lesions. METHODS Primary and permanent molars in children that were treated included those with extensive occlusal caries with undermined enamel in one or more cavity walls. Following local anesthesia and rubber dam application, cavity outline was prepared with a #330 tungsten bur, and the carious lesion removed. If an unsupported cusp was present, the inner enamel wall and the dentine floor adjacent to this wall was etched with a gel containing 37% phosphoric acid, rinsed and dried and Scotch bond multipurpose applied; a 1-mm layer of Z100 was applied to the unsupported cusp and polymerized; a nongamma 2 amalgam or Z100 was used to restore the tooth. RESULTS The children were re-examined after 6, 12 or 24 months. A total of 42 restorations were placed in 39 children (26 boys and 13 girls), ranging in age from 4 to 16 years (mean age 9 years, 6 months). This is a preliminary report on 30 restorations, followed up from 6 to 24 months. All 30 restorations were successful in preventing cuspal fracture. Four teeth developed caries in the proximal surface, but were unrelated to the restoration. CONCLUSIONS It was concluded that bonded composite can prevent fracture of unsupported cusps.