Shear bond strength of composite resin and amalgam adhesive systems to dentin

Purpose: To determine the effects of several multi-purpose dental adhesive systems on the shear bond strength of both composite resin (Herculite XRV) and amalgam (Tytin) to dentin. Materials and Methods: 160 extracted human molar teeth were randomly assigned to 16 treatment groups (n=10/group), embedded in resin, and ground flat on both the occlusal and apical surfaces to expose a 3.0 mm thickness of dentin. In each specimen, a 3.18 mm diameter channel was drilled through the dentin perpendicular to the ground surface. The cylindrical preparations were treated with one of seven adhesive systems or one of two controls (37% H3PO4 or Copalite varnish) according to manufacturers' recommendation, then restored with either composite resin or amalgam. Specimens were thermocycled and subjected to a punch-out shear force using a materials testing machine. Results: All examined multi-purpose adhesive systems provided increased shear bond strength in comparison to the controls. Although the individual performance of each adhesive system varied with specific restorative materials, OptiBond FL demonstrated the highest mean shear bond strength to both composite resin and amalgam. Mean amalgam shear bond strength was significantly greater than mean composite resin strengths.