White spots on teeth may be underdeveloped enamel or fluorosis. A common cause of white spots on teeth is enamel hypoplasia. The outermost part of the tooth is the enamel, which is normally colorless and transparent, and if calcium deficiency causes poor mineralization during calcification of the developing teeth, enamel hypoplasia of the teeth can occur. The teeth appear as opaque white patches. The period of calcification of teeth is during the fetal period, so maternal calcium deficiency during pregnancy may lead to incomplete calcification of teeth, and after birth, the calcification channels of teeth are closed, and then calcium supplementation is not effective, so dental calcium supplementation should be carried out during the fetal period. White spots on the teeth may also be caused by dental fluorosis, which can occur during fetal life or before the age of seven with a history of living in a high fluoride area, or if the fluoride content in drinking water is excessive. A chalky white change will appear on the surface of the teeth, and dental fluorosis is also a manifestation of systemic fluorosis in the mouth. In severe cases, cosmetic dental resin restoration is required. Tooth fluorosis needs to be solved at the root of the problem by controlling the fluoride content in water, solving industrial pollution, and treating industrial waste. Therefore, white spots on teeth may be caused by calcium deficiency during tooth development, or the manifestation of systemic fluorosis in the oral cavity.