Impact of a High-Power Light-Emitting Diode Unit With Reduced Curing Times on the Shear Bond Strength of Orthodontic Brackets and Their Adhesive Remnant Index Scores

Aim and objectives: This study aims to evaluate the curing time minimally required for bonding stainless-steel (SS) brackets using a high-power light-emitting diode (LED) light curing unit (LCU) and examine the debonded enamel surface for adhesive remnant. Materials and methods: Based on the LED LCU and curing time employed, 80 human maxillary first premolar teeth were equally segregated into four groups. Three groups were cured using a high-power LED unit (Guilin Woodpecker Medical Instrument Co., Ltd., Guilin, Guangxi, China) for one, two, and three seconds. The fourth group served as a control and was bonded with another intensive LED unit (Elipar™ S10 LED Curing Light; 3M, Saint Paul, Minnesota, United States) for 20 seconds. Transbond™ XT Light Cure Adhesive (3M, United States) adhesive was used for bonding the SS brackets. All the samples were exposed to shear bond strength (SBS) testing after a 24-hour immersion period in distilled water at 37°C. A stereomicroscope was used to examine and score the adhesive remnant on the debonded surface using a modified adhesive remnant index (ARI). Kruskal-Wallis-ANOVA and post-hoc Mann-Whitney U tests for multiple pairwise comparisons were performed to analyze the data. Results: Time and intensity significantly affected the SBS (P<0.001). A higher SBS value (16.04 megapascals (MPa)) was obtained in the six-second group when compared to the three-second (11.58 MPa), one-second (10.69 MPa), and 20-second control (13 MPa) groups. The ARI was significantly affected by the curing method. Conclusions: Higher SBSs were recorded for the six-second group using the high-power LED. A greater ARI score is associated with a reduced curing duration and vice versa.