The Effect of Different Light Intensities of LED Curing Units on the Bond Strength of Next-Generation Self-Adhesive Coated Metal Brackets

Background: Effective orthodontic bonding relies on proper light-curing techniques, as variations in curing mode and intensity can influence adhesive performance and clinical outcomes. This study aimed to investigate the effects of light emitting diode (LED) curing unit intensity and exposure duration on the shear bond strength (SBS) of APC Flash-Free metal brackets under in vitro conditions. Methods: Sixty human premolars were divided into three groups (n = 20). All procedures were identical, except for light-curing parameters. The curing process was carried out using an LED light-curing unit (VALO Ortho; Ultradent Products, South Jordan, Utah). Group 1 was cured in standard power mode (1200 mW/cm²) for 1 × 10 seconds; Group 2 was cured in high power mode (3200 mW/cm²) for 2 × 3 seconds; and Group 3 was cured in quadrant high power mode (3200 mW/cm²) for 2 × 3 seconds. SBS tests were performed using an Instron machine (Lloyd LF Plus; Ametek, UK). Shear bond strength (SBS) values and Adhesive Remnant Index (ARI) scores were analyzed using the Kruskal-Wallis H test (α = 0.05). Results: The highest mean SBS was observed in the standard mode group, and the lowest in the quadrant high-power mode group, but differences were not statistically significant (P = .670). Curing modes also showed no significant effect on ARI scores (P = .293). Conclusion: All tested modes showed comparable outcomes under in vitro conditions. For clinical applications, the use of the high-power mode is recommended, as it enables shorter polymerization durations; however, clinical studies or in vivo validation are required to confirm these findings.