Shear Bond strength of orthodontic bonding materials polymerized by high-intensity LEDs at different intensities and curing times

Abstract

© 2017 Trans Tech Publications, Switzerland. To evaluate and compare shear bond strength (SBS) and Adhesive Remnant Index (ARI) of orthodontic brackets polymerized by high-intensity light-emitting diode (LED) curing units at different intensities and curing times. Sixty extracted human upper premolar teeth were divided into 3 groups of 20 each. The tooth surfaces were prepared and the brackets were bonded on the teeth with light-cured adhesive and cured with 3 different light-curing units and conditions; Group 1 (Bluephase, 1,200 mW/cm2, 20 seconds), Group 2 (VALO, 3,200 mW/cm2, 6 seconds), Group 3 (FlashMax P3, 4,000-6,000 mW/cm2, 3 seconds). Shear bond strength of the specimens were tested after bracket bonding for 5 minutes. The means of shear bond strength among groups were compared by Kruskal-Wallis and Mann-Whitney U tests. ARI were tested by the Fisher's exact test (p < 0.05). The means and standard deviations of SBS in groups 1, 2 and 3 were 21.80 ± 2.85, 21.04 ± 2.87 and 4.75 ± 2.82 MPa, respectively. Group 3 had significantly lowest mean SBS. Significant difference of ARI was found between Bluephase and VALO groups (p = .010). FlashMax P3 curing at 3 seconds generated significantly lowest mean SBS among 3 groups. The SBS generated by VALO curing at 6 seconds was not significantly different from Bluephase curing at 20 seconds. Therefore, VALO can be an option for orthodontic bracket bonding benefited in reducing clinician chairtime and patient discomfort.