Effect of Different Bleaching Techniques on Microleakage under orthodontic Brackets: In Vitro Study

Statement of problem: Numerous studies report significant changes in tooth color that occur during orthodontic treatment. The adverse effects of bleaching procedures during orthodontic treatments have not been studied comprehensively.
This study investigated the effects of two methods of dental bleaching on the degree of microleakage beneath orthodontic brackets.
We selected 45 extracted premolar teeth and bonded them to orthodontic brackets. These teeth were stored in normal saline for 24 hours and thermocycled. We randomly divided the samples into 3 groups of 15 teeth per group. The first group (control) received no bleach treatment; the second group (office bleaching) was treated with 35% hydrogen peroxide (Whiteness HP Maxx); and the third group (home bleaching) was treated with 22% carbamide peroxide (Whiteness Perfect). The apices were sealed with sticky wax, rinsed in tap water, and air-dried. We applied nail varnish to the entire surface of each tooth, except for an area approximately 1 mm away from the brackets. The samples were immersed in basic fuchsine and cleaned after 24 hours. Microleakage was determined by direct measurement using a stereomicroscope. Kruskal-Wallis and Dunn post-hoc statistical tests, and SPSS software were used for statistical analysis. The significance level was set at P≤0.05.
The office bleaching group had significantly more microleakage scores under the brackets at both the occlusal (P=0.04) and gingival (P =0.040) margins of the brackets compared to the home bleaching group. The home bleaching group showed statistically more significant microleakage scores than the control group in both the gingival (P=0.006) and occlusal (P=0.014) margins of the brackets. All three groups had statistically more significant microleakage at the gingival margins of the brackets than the occlusal margins.
Office bleaching caused the most microleakage under the brackets and home bleaching caused more microleakage than the control group. We observed more microleakage at the gingival margins of the brackets compared to the occlusal margins.