Which of the following is not a property of fluoride?

Fluoride has several well-established properties that contribute to its role in dental health, particularly its protective effects against tooth decay. However, one property that does not apply to fluoride is its ability to produce extrinsic tooth stain.

Fluoride helps to strengthen tooth enamel and makes it more resistant to acid attacks, thereby reducing the risk of cavities. While excessive exposure to fluoride can lead to dental fluorosis, which may result in intrinsic staining or mottling of the teeth, this stain is not considered extrinsic. Extrinsic stains, by contrast, are typically caused by external factors such as food, drink, or tobacco products, and they occur on the surface of the teeth due to the accumulation of substances.

The other options represent properties of fluoride that are well-documented in dental studies. Fluoride can cross the placental barrier, meaning it can affect developing teeth in a fetus. It deposits in bone as it is consumed and absorbed, contributing to mineralization. Lastly, fluoride is also rapidly excreted by the kidneys, which helps regulate its levels in the body and prevent toxicity.