Objective: The study compared 2 Light Emitting Diode (LED) curing units with a universal testing machine for checking the shear bond strength and also evaluated adhesive remnant index (ARI). Methods: This in vitro study was carried out on sound 120 human extracted premolars. All the teeth were bonded with adhesive precoated metal brackets. The brackets were instantly set in place and confidently pressed against the tooth surfaces and polymerization of brackets was done with LED curing units [VALO and ELIPAR]. Both groups were further divided according to different debond times. SBS values in all the cases were measured at a crosshead speed of 1 mm/min and a 50-kg load cell. Significance for all statistical tests was pre-determined at p < .05. Results: In-vitro bond strengths for the LED curing units (Elipar and VALO) were 8.84±3.141 MPa and 9.87±5.591 MPa, respectively. Moreover, the shear bond strength was improving with time from 12 hours to 7 days in both the units. An equivalent distribution of the ARI (Adhesive Remnant Index) scores of 0, 1, and 3 was noticed for all debond times but an ARI score of 2 was not observed in this group. However, in LED unit (VALO) all the ARI scores (0, 1, 2, 3) were observed at different deboning times. Conclusions: The results revealed that the shear bond strength (MPa) improved with time from 12 hours to 7 days in both the curing units.
Key words: Curing lights; Bond strength; Debond time; Orthodontic brackets.