Demineralization-induced white spot lesions (WSL) are early non-cavitated carious lesions, representing the earliest stage of tooth decay, and appear as opaque, milky, porous areas, with a depth of only 40–130 μm. They are frequently found postfixed orthodontic treatment, because of the retentive nature of brackets and wires, and the inherent difficulties in maintaining proper oral hygiene, but can be found in non-orthodontic patients, as well. The main concern is of esthetic nature, but untreated WSL may evolve in dental caries, with important structural and functional consequences. The treatment approach more often uses conservative methods such as remineralization, microabrasion, tooth whitening, and resin infiltration, but, depending on the case, resin restorations and veneers may be involved. This chapter aims to discuss their etiology, characteristics and diagnosis, prevention and treatment methods, and to present three clinical cases of demineralized induced WSL, of orthodontic and non-orthodontic origin, treated by means of a microinvasive method, namely resin infiltration.