This case report presents the technique of deep infiltration for the treatment of hypomineralized enamel lesions in a patient affected by molar incisor hypomineralization (MIH) with the purpose of obtaining an aesthetic improvement in the affected vestibular enamel. Deep infiltration treatment involves a sequence of steps starting with an initial mechanical abrasion of the outside surface of the enamel, followed by a phase of chemical erosion using 15% hydrochloric acid, penetration through the porosity of the enamel by a very fluid resin, and finally the repair of the thin layer of lost enamel using a composite. The aesthetic improvement of the elements affected by hypomineralized lesions is discernible immediately following treatment and becomes more accentuated with time. At the expense of minimal damage to surface enamel, deep infiltration enables treatment of all types of white spot enamel lesions, regardless of aetiology, offering the possibility of restoring an aesthetically pleasing smile for patients.