Sometimes permanent teeth erupt with stained enamel. These spots can be white (like chalk) or brown. They are caused by alterations in enamel mineralization during tooth formation. They occur during pregnancy and there are different degrees of affectation, the most serious is when the enamel breaks and presents as cavities in the tooth. When it affects the molars, they are more susceptible to cavities.
Photos before and after treatment, in this case with porcelain veneers