SURFACE-TREATMENT EFFECTS ON AMALGAM REPAIR STRENGTH

Purpose: To determine whether the use of microetching and bonding agen ts could improve the shear bond strength between aged and freshly adde d dental amalgam, simulating an amalgam repair. Materials and Methods: Aged amalgam surfaces were treated with either a carbide bur or carbi de bur + microetcher (Al2O3 abrasive). Five commercially-available adh esive systems were tested. Fresh amalgam was condensed through a split mold onto each prepared amalgam surface. Two control groups were incl uded: a positive control consisting of non-repaired amalgam, and a neg ative control consisting of aged specimens which received neither carb ide bur nor microetching preparation prior to the addition of fresh am algam. In addition, one group received only carbide bur and another re ceived only carbide bur and microetching treatments, without any adhes ive. Following storage and thermocycling, each specimen was tested for shear bond strength. Results: The mean shear bond strength of the rep aired samples treated with carbide bur alone (25.8 MPa) was not exceed ed by any of the other treatments. Neither microetching nor use of an adhesive agent significantly improved amalgam-to-amalgam shear bond st rength. In some cases, use of an adhesive agent significantly decrease d the shear bond strength of repaired amalgam samples.