INFLUENCE OF TEMPERATURE AND RELATIVE-HUMIDITY ON EARLY BOND STRENGTHS TO DENTIN

The effect of temperature and relative humidity (RH) on the early tens ile bond strengths to bovine dentine of two bonding systems (Liner Bon d System, and Scotchbond Multi-purpose), and an experimental system (K B-110) were tested. Two environmental conditions, room temperature (23 degrees C/50% RH) and oral temperature (30 degrees C/80% RH), were us ed in a controlled temperature and humidity chamber. Bond strengths we re recorded immediately after, 10 min and 24 h following light curing. The tensile bond strengths did not vary between the two test conditio ns, but the mode of fracture was observed to change. The 30 degrees C/ 80% RH condition exhibited a slightly greater degree of adhesive type failures compared with the 23 degrees C/50% RH group. This was particu larly so for the experimental system, indicating that different bondin g systems may be more or less sensitive to changes in RH and temperatu re. Failures occurred partially or totally within the resin composite at the early test times, and it was concluded that the bond strengths of the systems tested tended to exceed the early cohesive strengths of the resin composite.