Study of the Effect of Different Intensity and Duration of LED Light on Shear Bond Strength and Adhesive Remnant Index of Metal Orthodontic Brackets

Bonding of orthodontic brackets of fixed orthodontic appliance by using acid etch technique was first introduced in 1955. LED-based light sources posses many benefits as minimal heat generation. There is a new generation of LED light cure corporate with three different intensities (standard, high power and extra power).

This study was aimed to evaluate the effect of increasing intensity and decreasing duration of LED light on shear bond strength and adhesive remnant index of metal orthodontic brackets.

Sixty healthy extracted maxillary premolars were divided into three groups of twenty teeth for each, group (I) cure with a standard LED light curing (1000mW/cm²) for 10 seconds, group (II) cured through a high-intensity LED curing light (1400mW/cm²) for 8 seconds, group (III) cured with a extra high-intensity LED curing light (3200mW/cm²) for 6 seconds. The teeth mounted in acrylic resin, Shear bond strength test was done. Then, adhesive remnant index (ARI) was evaluated. Data were analyzed by one-way analysis of variance ANOVA test and LSD, and Fisher exact test.

The results showed that there were statistically significant differences among the study groups. The maximum value of shear bond strength was for group III (17.834 ± 0.367) and the minimum shear bond strength value was for group I (8.888 ± 0.307). ARI scores showed a statistically significant differences among groups, with a high tendency toward score 1 and score 0 in all three groups.

High intensity LED light with low curing duration has advantage of increasing bond strength in addition to reducing chair time taken for curing procedure and enamel cleaning following de-bonding procedure without any effect on the enamel integrity.