Understanding dental caries, its progression and proper diagnosis in early stages has become a challenge in clinical practice, research, and prevention. Tooth decay is a dynamic disease affecting the tooth’s surface in contact with bio-film, resulting in mineral loss, which leads to the localized destruction of the tooth’s hard tissue. During the early stages of the carious lesions there is an increase in enamel micro-porosity, which clinically appears as opacity or a stain that can be either white or brown. As micro-porosity increases, tooth structure collapses forming a cavity. This process is slow, and according to the evidence it can be stopped before the cavity appears. The carious process is highly variable, with periods of progression alternating with periods of stability; therefore, diagnostic methods must seek to detect the aforementioned changes, in order to determine the stage at which the disease can be arrested. In consequence, the development of an effective diagnostic method has been the goal of many researchers for a long time.