Laboratory study of the Herculite XR system

The shear bond strengths of the Herculite XR system to dentin were determined the quantitative microleakage of Class V restorations in dentin evaluated; the fluoride release from the XR-Ionomer determined, and fractured test specimens depicting various failure patterns examined in the scanning electron microscope. The shear bond strength of the XR-Ionomer to dentin was 6.6 +/- 1.7 MPa and the Herculite XR 15.4 +/- 3.7 MPa. Sixteen of the 20 Herculite XR test specimens fractured in dentin. The quantitative microleakage of Class V Herculite XR restorations in dentin was 2.22 +/- 1.94 micrograms dye which was significantly reduced to 0.91 +/- 0.63 micrograms when the XR-Ionomer was placed in the floors of the preparations. The fluoride release from the XR-Ionomer dropped sharply during the first 6 days after which it reached a plateau at approximately 0.5 microgramsF.mm-2.