Enamel specimen preparation
ALDRICH
Twenty extracted pristine human third molars disinfected and stored in 0.5% thymol (Sigma Aldrich, St. Louis, USA) solution at 4 °C for at least 1 week were utilised for preparation of enamel specimens. Using a microtome saw (SYD Mikki Pulley, Aichi, Japan), the enamel specimens were sectioned in the dimensions of 3 × 3 × 2 mmBefore experimental cycles, the enamel specimens were embedded in resin cement (RelyX Unicem, 3 M ESPE, St. Paul, USA) with the enamel surface exposed. Then, the resin-enamel surfaces were sequentially polished with silicon carbide paper of 220, 600, 1000, 2000, and 4000 grit (Buehler, Lake Bluff, IL, USA). The specimens were cleaned in an ultrasonic cleaner (Wise Clean WUC-D10H, Daihan, Seoul, South Korea) for 5 mins while immersed in deionized water (DIW) prior to being subjected to baseline characterizations.