Shear strength and filler particle characterization of Maryland (acid etch) bridge resin cements

The shear strengths of Maryland (acid etch) bridge cements were investigated and ranged from 44 to 70 MPa. The bulk shear strength of the resin cements is sufficient; the weak link in the system (other than the technique sensitivity) is the interface at or adjacent to the resin and metal or the resin and enamel. The resin cements were polished and etched, and scanning electron micrographs were taken and digitized to illustrate the filler particle sizes and distribution.