Bonding agent is a decisive factor in determining the marginal leakage of dental composites subjected to thermal cycling: an in vitro study

The marginal leakage at the dentine/composite interface in Class II composi te restorations subjected to thermal cycling has been effectively evaluated using the silver staining technique. The presence of a bonding agent at th e dentine/composite interface is found to improve adhesion. Scanning electr on and optical microscopic observations of sectioned specimens reveal that applying a second coat of bonding agent on the dentinal surface helps in re ducing microleakage compared to a single coat application, in all three rad iopaque composite/bonding agent systems studied (Z1001Single Bond, Spectrum TPH/Prime & Bond 2.1 and Chitra/Chitrabond 1.0). Thermal cycling during in vitro studies was found to provide a more appropriate representation of th e adhesive behaviour of the composite in clinical situations.