EFFECT OF COMBINATIONS OF SURFACE TREATMENTS AND BONDING AGENTS ON THE BOND STRENGTH OF REPAIRED COMPOSITES

Statement of problem. Enhancement of bond strength between new and old composite usually requires increasing the surface roughness to promot e mechanical interlocking and coating of old composite with unfilled r esin bonding agents to advance surface wetting and chemical bonding. P urpose. The purpose of this study was to evaluate the effect of combin ations of surface treatments and bonding agents on the shear bond stre ngth between new and old composite. Material and methods. Sis surface treatments, two bonding agents, and an untreated control comprised 18 different subgroups. Results. The use of unfilled resin, alone or comb ined with silane, was the most effective procedure to enhance the shea r bond strength of the repaired composite specimens, irrespective of t he surface pretreatment processes. Silanation and unfilled resin sligh tly but not significantly improved the repair strength compared with u nfilled resin alone. Conclusions. Different combinations of surface tr eatments and bonding agents affect shear bond strength differently. Th e highest shear bond strength values were achieved by grinding the sur face with green Carborundum stone or sandblasting, whereas the lowest values were obtained with hydrofluoric acid as the surface treatment a gent.