Dental fluorosis occurs because of the excessive intake of fluoride either through naturally occurring fluoride in the water, water fluoridation, toothpaste, or other sources. The damage in tooth development occurs between the ages of 6 months to 5 years, from the overexposure to fluoride. Teeth are generally composed of hydroxyapatite and carbonated hydroxyapatite; when fluoride is present, fluorapatite is created. Excessive fluoride can cause yellowing of teeth, white spots, and pitting or mottling of enamel. Consequently, the teeth become unsightly. Fluorosis can not occur once the tooth has erupted into the oral cavity. At this point, fluorapatite is beneficial because it is more resistant to dissolution by acids (demineralization).

Although it is usually the permanent teeth which are affected, occasionally the primary teeth may be involved. In mild cases, there may be a few white flecks or small pits on the enamel of the teeth. In more severe cases, there may be brown stains. The differential diagnosis for this condition may include Turner's hypoplasia (although this is usually more localized), some mild forms of amelogenesis imperfecta, and other environmental enamel defects of diffuse and demarcated opacities.