Fluorine is essential for preventing which of the following conditions?

Fluorine plays a crucial role in dental health, particularly in the prevention of tooth decay and the maintenance of healthy enamel. It helps to rebuild weakened tooth enamel and can make teeth more resistant to acid attacks from plaque bacteria and sugars in the mouth. This is why fluorine is associated with the prevention of poor teeth and dental caries.

In contrast, the other conditions listed are not directly related to fluorine. Rickets is caused by a deficiency of vitamin D, calcium, or phosphate, which is necessary for proper bone health. Goiter is primarily associated with iodine deficiency, which affects thyroid function and hormone production. Anemia is typically the result of a lack of iron, vitamin B12, or folate, none of which involve fluorine. Thus, recognizing that fluorine specifically contributes to dental health clarifies its role in preventing poor teeth.