Why do you need to brush your baby teeth that are going to fall out?

What did people use to brush their teeth before the toothbrush was invented? What food can be used as an emergency toothbrush? How much toothpaste should you use? For free home activities sign-up at www.WhoSmarted.com See Privacy Policy at https://art19.com/privacy and California Privacy Notice at https://art19.com/privacy#do-not-sell-my-info.