To protect the teeth against dental decay itâs important to use toothpaste when brushing. Cavities in the teeth develop when the harmful bacteria that exists in the mouth produce acids which then eats a hole in the toothâs enamel. By brushing your teeth with a toothpaste containing fluor twice a day, the teeth are protected and the risk of developing cavities are reduced. Mouthwash can be used as a supplement to toothpaste to strengthen the enamel and prevent cavities.