Quercetin solution

The content of flavonoids in the plant extracts was determined as described by Macioszek et al. [35 (link)]. Briefly, 600 µL of plant extract, 1800 µL of 80% methanol, 120 µL of 10% aluminum chloride hexahydrate, and 120 µL of 1 M sodium acetate were mixed. After 30 min of incubation in the dark, the samples were transferred to a 96-well plate and analyzed spectrophotometrically at a wavelength of 415 nm. The content of flavonoids was calculated based on the absorbance of the standard quercetin solution (Sigma-Aldrich, Poznan, Poland) and expressed as mg g⁻¹ FW.

The teeth were randomly divided into four groups (n = 24) based on the pretreatments used: (1) Group A (control): no pretreatments; (2) Group B: 2% CHX solution (Consepsis; Ultradent, South Jordan, UT, USA) (Coelho et al., 2020 (link)); (3) Group C: a 10% α‐tocopherol solution was prepared by dissolving 10 g of α‐tocopherol gel (Sigma‐Aldrich, St. Louis, MO, USA) in 100 ml of ethyl alcohol in a standard flask (Kavitha et al., 2016 (link)); and (4) Group D: a 1% quercetin solution (Sigma‐Aldrich) was prepared by dissolving 1 g of quercetin powder directly into pure ethanol under water‐bath heating at 37°C (Li et al., 2017 (link)). The pretreatment solutions were actively applied to the dentin surface by tapping with a microbrush. After 60 s, the teeth were rinsed with water for 10 s and gently dried with a cotton roll.