Effect of Different Light-tip Distances on Shear Bond Strength of Orthodontic Brackets Cured with Light-emitting Diode and High-intensity Light-emitting Diode

Abstract

Aim: The aim was to find out whether the light-tip distance affected the shear bond strength of orthodontic brackets when cured with light-emitting diode (LED) and high-intensity LED at four different light-tip distances. Materials and methods: Extracted human premolars were divided into eight groups. Each tooth was embedded in the self-cure acrylic resin block, and brackets were bonded and cured with different lights and different distances. Shear bond strength tests were performed in vitro using the universal testing machine. Data were analyzed using one-way ANOVA test. Results: The descriptive statistics for shear bond strength of orthodontic brackets cured with LED light at 0 mm was 8.49 ± 1.08 MPa, at 3 mm was 8.13 ± 0.85 MPa, 6 mm was 6.42 ± 0.42 MPa, and at 9 mm was 5.24 ± 0.92 MPa, and those cured with high-intensity light at 0 mm was 19.23 ± 4.83 MPa, at 3 mm was 17.65 ± 3.28 MPa, at 6 mm was 13.04 ± 2.36 MPa, and at 9 mm was 11.74 ± 1.4 MPa. Mean shear bond strength was found to decrease as the light-tip distance increased with both light sources. Conclusion: Shear bond strength is higher when the light source is close to the surface to be cured, and it decreases as the distance increases. The highest shear bond strength was achieved with high-intensity light. Clinical significance: Light-emitting diode or high-intensity units can be used for bonding orthodontic brackets without compromising the shear bond strength of the brackets, and that shear bond strength is stronger when the light source is close to the surface to be cured, and it decreases as the distance increases between the light source and the surface.