Treatment and erosive cycles
A single trained examiner applied a thin layer of varnish to the enamel specimens randomly distributed to the respective groups, primarily based on PLM and experimental/control treatment. The varnish coated specimens were then immersed in 15 ml of artificial saliva for 6 h. Then, the varnish was gently removed from the specimens with the help of a scalpel blade, and the specimens were rinsed in DIW and dried using fibreless laboratory napkins (Kimwipes, Kimberly-Clark Professional, TX, USA). Erosive challenge by the PLM then commenced. The specimens were subjected to 5 min of erosive attack by the respective PLM every 12 h, for 4 days. After each erosive attack, the specimens were rinsed with DIW, dried, and suspended in freshly prepared artificial saliva. After the last erosive challenge, the specimens were stored in 15 ml of artificial saliva for 24 h, before being removed for post-erosive cycle characterizations. While awaiting characterizations, the specimens were stored in a 100% moist environment assembled using 0.5% thymol solution.