The effect of thermocycling in microleakage analysis

The purpose of this study was to evaluate the effect of thermocycling on dye penetration during in vitro microleakage analysis of composites. Fifty non-carious human molars, stored in 75% ethanol, were divided into five groups (N = 10). Each tooth was prepared for a MOD slot preparation using a high speed handpiece and water, one proximal cervical margin in cementum, the other in enamel. The enamel margins were etched, rinsed, dried, and the composite inserted and cured in multiple increments. Group A was not thermocycled (TC) and was immersed in 0.5% basic fuchsin dye for 24 h at 37 degrees +/- 1 degrees C. Group A' was not TC and was immersed in 0.5% basic fuchsin dye for 4 h at 37 degrees +/- 1 degree C. Group B was TC in a water bath and immersed in dye as with Group A, Group B' was TC and immersed in dye as in Group A'. Group C was TC, as in Group B, but in a basic fuchsin dye bath. Thermocycling consisted of 250 cycles, 15 s dwell time each in 5 degrees C and 50 degrees C bath. The teeth were mounted in acrylic, and multiple cross-sections of all surfaces were prepared. Dye penetration was read on a scale of 0 (no leakage) to 4 (leakage to the pulpal floor) and means calculated for each surface and tooth. There was no significant increase of microleakage in restorations when thermocycling was used to simulate temperature extremes, either in dye or water baths, as opposed to restorations which were not thermocycled.