New High Intensity Light-Emitting Diode (LED) Curing Lights: An in vitro Evaluation of Increased Power Density at Reduced Curing Times

Introduction: The purpose of this study was to evaluate two new light-emitting diode (LED) curing lights with increased power densities at reduced curing times. Methods: Ninety extracted bovine incisors were examined in vitro. The incisors were divided into six test groups and metallic adhesive pre-coated brackets were bonded using either the Valo Otho (Opal Orthodontics, Ultradent) @ 3200 mW/ cm 2 or the Ortholux Luminous {3M Unitek)@ 1600 mW/ cm 2 at curing intervals of 3-, 6-, or 12-seconds. The samples were stored for 24 hours in 37 degree Celsius water and debonded. Brackets were tested using an MTS Mini-Bionix II testing machine at a crosshead speed of .5 mm/minute. The bracket failure interface was analyzed using an adhesive remnant index (ARI) score. Data were analyzed using Shapiro-Wilk t ests two-way ANOVA procedures, and Kruskal Wallis tests (ARI scores). Results: No significant differences were found in the mean shear bond strengths produced by each of the curing lights at the different curing times or between the two lights at the same curing times. Mean (±SD) shear bond strengths (MPa) for the Valo Ortho at 121 6 and 3 seconds were 27.82 ± 7.06, 26.97 ± 4.31, 26.95 ± 6.42, respectively; and for the Ortholux Luminous at 12, 6 and 3 seconds were 28.37 ± 4.92, 25.72 ± 4.98, 24.99 ± 4.92, respectively. In terms of total energy density, the varying power densities at different combinations of curing time did not produce shear bond strengths that were significantly different between any of the test groups. Further, there were no significant differences between ARI scores for each of the LED lights following debonding. Conclusion: These results indicate that there are no statistically significant differences between the bond strengths produced when using the Valo Ortho (Ultradent) or the Ortholux Luminous (3M Unitek) for 3-, 6-, or 12-seconds. Also, 3 second exposure times produced bond strengths that appeared similar to those produced at 6- and 12-seconds when using either light