CUSP FRACTURE-RESISTANCE IN COMPOSITE-AMALGAM COMBINED RESTORATIONS

Objective: To evaluate the in vitro resistance to fracture and microle akage in composite-amalgam combined restorations. Methods: Seventeen C lass I cavities with unsupported enamel walls prepared in extracted pe rmanent molar teeth were treated with a bonding agent (Scotchbond MP, 3M Dental), the buccal cusps were reinforced with a composite resin (Z -100, 3M Dental) and the cavities were then restored with amalgam (Per mite, Oral B). All teeth were load tested using a special fatigue-stre ss apparatus, immersed in a dye solution and then sectioned for examin ation by stereomicroscopy and scanning electron microscopy (SEM). Resu lts: Fractures in enamel supported by composite were present in 11 cas es while 12 specimens included fractures in enamel supported by bonded amalgam. Microleakage was observed in 16% of the enamel-amalgam inter faces, 10% of the dentin-amalgam interfaces, 7% of the amalgam-composi te interfaces, 4% of the composite-enamel interfaces and 11% of the co mposite-dentin interfaces. Conclusions: Bonded amalgam appears to be a s effective as bonded composite in supporting undermined enamel in ter ms of resistance to fracture, but composite may have better marginal a daptation to enamel compared to bonded amalgam. Good marginal adaptati on may be observed between amalgam and composite in composite-amalgam restorations. (C) 1998 Elsevier Science Ltd. All rights reserved.