Final answer:
Fluorosis affects the enamel, the outermost layer of the tooth, causing discoloration and surface irregularities due to high fluoride levels. In contrast, optimal fluoride levels strengthen the enamel by forming fluorapatite and helping to prevent cavities.
Step-by-step explanation:
Impact of Fluorosis on Tooth Layers
Fluorosis primarily affects the enamel layer of the tooth. Enamel is the outermost layer that provides protection against decay. When fluoride levels in drinking water are high, it can lead to dental fluorosis, which alters the appearance of the enamel. It can cause discoloration and surface irregularities. However, fluoride at optimal levels is beneficial, as it reacts with the hydroxyapatite in enamel to form fluorapatite, making the enamel more resistant to acid attacks by bacteria in the mouth, therefore, preventing cavities.
Excessive fluoride, on the other hand, can disrupt the normal development of enamel, leading to the characteristic mottling of fluorosis. While the intent of water fluoridation and fluoride-containing dental products is to support oral health by preventing tooth decay and promoting remineralization, careful monitoring of fluoride levels is essential to avoid the adverse effects of fluorosis.