Table 1. The experimental groups.

Groups	Enamel type	Storage
SE (positive control)	Sound enamel	100mL of deionized water, changed daily for eight weeks
DE (negative control)	Demineralized enamel	100mL of deionized water, changed daily for eight weeks
AS (artificial saliva)	Demineralized enamel	100mL of artificial saliva, changed daily for eight weeks
NaF (0.05% fluoride solution)	Demineralized enamel	Immersed daily for one minute in 1mL of 0.05% NaF solution for eight weeks, then rinsed with deionized water and stored in artificial saliva
Ic (resin infiltration)	Demineralized enamel was resin infiltrated (Icon, DMG, Hamburg, Germany)	100mL of artificial saliva, changed daily for eight weeks