Comparison of shear bond strength of orthodontic bracket bonding to teeth using light-curing units between halogen and LED: An in vitro study

Abstract

Background: Light-cured bonding systems have been widely accepted among orthodontists. Various light curing units are available now. Recently, the light emitting diode (LED) has been introduced alongside halogen light curing units. There is lack of information on the advantages and disadvantages of different light curing systems. The aim of this in vitro study was to compare the shear bond strength of orthodontic brackets and adhesive remnant index (ARI) of an adhesive cured with two different orthodontic light sources i.e. LED and halogen. Methods: Forty four (22 in each group) extracted human premolars without any defects were etched with 37% phosphoric acid and cleansed with water spray and air dried. The sealant (Ortho Solo) was applied on the tooth surface and the brackets were bonded using adhesive (Enlight). Adhesives were cured with Halogen (Litex) and LED (D-LUX) for 40 seconds. Then the specimens were debonded later using a universal testing machine, with crosshead speed of 0.2 mm/min until the brackets were detached. Adhesive remnant index (ARI) scores were assessed under stereomicroscope at ×10 magnification. Results: The shear bond strength in Halogen group was 19.73 ± 3.44 MPa and in the LED group 20.81±3.02 MPa which is little higher than halogen group. The proportion of being adhesive remaining index for ARI Score 1 in Halogen group was 5 (22.7%) and in LED group 7 (31.8%). While ARI Score 2 in the Halogen group was 13 (59.1%) compared to LED group 8 (36.4%). However, ARI Score 3 in Halogen group was 4 (18.2%) and in LED group 7 (31.8%). The overall model showing no significant difference. Conclusion: Within limitations, this in vitro study showed the shear bond strength of orthodontic adhesives cured with a LED was statistically equivalent to those cured with a halogen light curing unit. There were significant differences in the ARI scores of the light-curing units tested. LED light-curing units can be suggested for the polymerization of orthodontic bonding adhesives because it showed a balanced effect on ARI index. Bangladesh Med Res Counc Bull 2019; 45: 17-22