The mineral commonly used in toothpaste is fluoride. Fluoride is added to toothpaste because of its ability to strengthen tooth enamel and helps prevent cavities. It works by remineralizing the enamel surface, making it more resistant to acid attacks from bacteria and sugary foods. Additionally, fluoride can inhibit the growth of harmful bacteria in the mouth. Its effectiveness in dental care has led to widespread use in oral hygiene products, contributing to better overall dental health and reducing the incidence of tooth decay among populations.