Eco etch

After preparing the enamel surface, it was etched for 30 s using 37% orthophosphoric acid gel (Eco-Etch Ivoclar Vivadent), properly washed with water, and gently dried with oil-free air.
The next step involved applying a thin coating of TE-Econom Bond Dental Adhesive (Ivoclar Vivadent), gently blowing it with a jet of oil-free air, and then curing the adhesive for 20 s using a 1200 mW/cm² LED-curing light (LED-D Light Cure, Guilin Woodpecker Medical Instrument Co., Ltd., China).

The study involved 40 caries-free human maxillary premolar teeth that had been freshly extracted as part of courses of orthodontic treatment. The teeth were cleaned using an ultrasonic scaler and stored in distilled water at 37°C.
The teeth were randomly divided into two groups of 20 (A and B). Nano-Bond adhesive (Pentron Clinical Technologies LLC, Orange, CA, USA) without additives was used for Group A (the control group) while the Nano-Bond adhesive with 0.05% AgNPs was used for Group B. Both groups were divided into four subgroups, each containing five teeth. The teeth were subjected to subgroup-specific thermal and loading stress, as shown in Table 1. The bracket bonding procedure was based on acid etching the enamel, following the procedure developed by Buonocore in 1955,[12 ] using phosphoric acid gel at a concentration of 37% (Eco-Etch, IvoclarVivadent AG, Schaan, Liechtenstein). The enamel was then rinsed with water and dried with oil-free stream for five s. Primer was applied to the etched surface using an applicator brush the excess primer was removed using a dry applicator brush, but the surface was left with a very wet appearance. The enamel was then light-cured for 10 s using a 430-490 nm light-emitting diode (LED; BG Light Ltd, Plovdiv, Bulgaria).