Dentin-polymer bond in resin fillings tested in vitro by thermo- and load-cycling.

The effect of stress applied by thermo- and load-cycling to the bond between composite- and bonding-agent-treated dentin was tested. Cylindrical cavities in extracted human teeth, approximately one-half of the margins in dentin, were etched and treated with two bonding agents - Gluma and Clearfil Bond - before being filled with Silux composite. Forty specimens, some provided with cavity floor lining, were cycled several hundred times between 15 degrees and 50 degrees C, either immediately after light-curing or upon 24 hr of water storage. In all cases, microscopic inspection revealed unchanged adaptation at the dentin margins. Teeth with Class 3 and Class 5 cavities, ten of each and with the gingival margins entirely in dentin, were pre-treated and filled as above. The teeth were covered with a dye during loading and unloading in a manner simulating biting and chewing. Inspection of the cavity margins revealed absence of percolation at the dentin margins. It is concluded that effective bonding agents are necessary to prevent contraction gaps in resin-filled cavities where the margins are partly or entirely located in dentin.