Excess presence of which of the following causes tooth decay in children?

Tooth decay in children is primarily caused by the excess presence of fluoride. Fluoride is a naturally occurring mineral that can be found in various sources such as water, food, and dental products. It is commonly added to toothpaste and water supplies to help prevent tooth decay.
However, when there is an excessive amount of fluoride, it can have negative effects on dental health. This is particularly true for children whose teeth are still developing.
Excess fluoride can cause a condition called dental fluorosis, which affects the outer layer of the teeth called the enamel. Dental fluorosis leads to the formation of white or brownish stains, and in severe cases, it can cause pitting or mottling of the teeth.
It's important to note that fluoride in optimal amounts is beneficial for dental health, as it helps to strengthen enamel and prevent tooth decay. The key is to ensure that children are exposed to fluoride in appropriate concentrations.
In summary, the excess presence of fluoride can cause tooth decay in children by leading to dental fluorosis, resulting in discoloration and damage to the tooth enamel.