The exposure to each bath was 30 seconds and the transfer time between the two baths was 5�C10 seconds. 500 cycles between 5��C and 50��C were in accordance with the recommendation of the International Organization for Standardization (ISO/TS 11405).12 The other 10,000 cycles were performed to demonstrate long-term exposure to moisture at oral temperature. The PAC light was calibrated thorough by inserting the curing tip completely into the calibration port and then depressing the hand switch. The halogen light was calibrated by placing the fiber-optic probe directly on the top of the built-in sensor until the light indicated that the probe intensity was adequate. A universal testing machine (LF Plus, LLOYD Instruments, Ametek Inc., England) was used for the shear bond test at a crosshead speed of 1 mm/min.

Force was applied directly to the bracket�Ctooth interface using the flattened end of a steel rod. The load at failure was recorded by a personal computer connected to the test machine. SBS values were calculated as the recorded failure load divided by the surface area (bracket base) and were expressed in megapascals (MPa). After debonding, the enamel surface of each tooth and the bracket bases were examined with a stereomicroscope (magnification ��10) by one investigator (S.H.S.) to determine the amount of residual adhesive remaining on each tooth. The adhesive remnant index (ARI) was used to assess the amount of adhesive left on the enamel surfaces.10 This scale ranges from 0 to 3.

A score of 0 indicates no adhesive remaining on the tooth in the bonding area, 1 indicates less than half of the adhesive remaining on the tooth, 2 indicates more than half of the adhesive remaining on the tooth, and 3 indicates all adhesive remaining on the tooth with a distinct impression of the bracket mesh. Statistical analysis Two-way analysis of variance was used to obtain the significant differences among curing lights, thermocycling, and their interactions. All treatment combination means for bond strength values were compared using the Tukey multiple comparison test (��=.05). The chi�Csquare test was used to compare the bond failure of ARI scores among the groups. RESULTS The two-way analysis of variance showed a significant difference for curing lights (P<.001) and thermocycling (P<.01). However, there was no interaction between light curing and thermocycling (P=.

177). The statistical results of SBS are presented in Tables I and II. It was found that the groups that did not undergo the thermocycle process (Groups I and IV) revealed higher SBS values than the thermocycled groups. Batimastat The comparison of both the groups indicated that the halogen groups demonstrated higher mean SBS than the PAC groups. Both groups showed a significant reduction between no cycles and 10,000 cycles (P<.05). Table III shows the distribution of ARI scores expressed as the frequency of occurrence.