Advancement in orthodontic bonding: comparing 1-second and 5-second light emitting diode (LED) curing lights

Recent advancements in dentistry have introduced new light-curing units such as 1-second and 5-second LED curing lights to orthodontics. We aimed to evaluate the shear bond strength and Adhesive Remnant Index (ARI) of stainless-steel orthodontic brackets cured with 1-second, and 5-second LED curing lights. Ninety human extracted upper premolars were selected based on the inclusion and exclusion criteria. The selected teeth were randomly divided into 2 groups - Group I and Group II. In Group I, the teeth were bonded with Standard pre-adjusted edgewise upper premolar brackets (Orthox, JJ Orthodontics) using Transbond XT and cured with Woodpecker iLED 1-second curing light. In Group II, the same brackets and composite were used to bond and light-cure with 5-seconds Woodpecker LED-D unit. The shear bond strength and the Adhesive Remnant Index (ARI) of brackets in both groups were evaluated. Student t-test was used for the statistical analysis of the data. In Group-I (1-second LED curing light), the shear bond strength was 6.62 MPa, whereas it was 10.32 MPa in group II (5-second LED curing light). A highly significant difference was observed in the shear bond strength between the groups. The ARI scores further revealed that the 5-second curing light resulted in a safer failure mode, with adhesive remaining mostly on the bracket. We found that the 5-second Woodpecker LED-D curing light demonstrated higher shear bond strength compared to the 1-second iLED curing light, although both sets of bond strength values are clinically acceptable.