Chelon Silver (C), Ketac-Silver Aplicap (K), Miracle Mix (M) silver-reinforced glass ionomers, and Valiant PH.D were evaluated as in vitro repair materials for cores. The core materials were placed in a 6 x 3 mm mold and stored at 37 degrees C at 100% RH for 24 hours. The cores were roughened with a coarse diamond. Five samples were conditioned (T) with Dentin Conditioner for 20 seconds, whereas another 5 samples were untreated (U). The cores were then repaired with C, K and M and subsequently tested after additional storage for 24 hours. Bond strength (MN/m2) was measured in tension using an inverted cone bond test at a crosshead speed of 0.05 cm/min. Mean bond strengths (S.D.) for the three repair materials when averaged over the three glass ionomer cores were: K, 5.0 (1.2); M, 3.4 (1.2) and C, 2.7 (1.5) for condition U; and M, 4.2 (1.1); K, 3.4 (1.2); and C, 3.1 (1.0) for condition T, where M, K and C were the repair materials. The Tukey intervals at the 95% level were 0.7 among materials and 0.5 between treatments. Bond strength of repaired amalgam was only successful with M, 0.9 MN/m2. Bond strengths to untreated silver-reinforced glass ionomer cores were higher with K used as a repair material.