Fracture resistance of four core materials with incorporated pins.

This study investigated the influences of pin type (stainless steel or titanium), number of pins (0, 2, or 4), and pin orientation (parallel or perpendicular to tensile forces) on the fracture resistance of four core materials: amalgam, composite resin, and two alloy-reinforced glass-ionomer cements. Analysis of variance revealed significant differences among materials, number of pins, and pin orientation. The fracture resistance of amalgam was reduced most by pins, followed by composite resin. The least strength reduction was found in alloy-reinforced glass ionomers, and in some pin orientations, fracture resistance was doubled compared to the controls. The most favorable pin orientation was parallel to tensile stresses. As the number of pins incorporated in amalgam was increased, fracture resistance decreased.