Too much fluoride
Now, fluoride is usually beneficial for dental hygiene. However, excessive fluoride consumption can lead to a condition called fluorosis, which can lead to white spots on developing teeth.
“Too much fluoride, either administered from over-fluoridated water sources or excessive ingestion of fluoride supplements during tooth development, may contribute to tooth discoloration by causing the development of white or brown spots or pitting of the enamel, which can darken over time,” says Dr. E. Lisa Reid, DMD, a prosthodontist in New York City, to Allure.