Hard boil eggs seven minutes with a few teabags in the water. The eggs will come out slightly brown. Place paper towels in the bottom of a basket or plastic container then top it with an egg. Allow the children to put toothpaste on a brush and brush the egg clean. The tea stain should come off easily, showing them how the toothbrush made it clean and white.
Print a picture of a big tooth on gray or pale yellow paper. Mix white paint with a little white mint-flavored toothpaste and some glitter and make sure they do not put it in their mouths. Instead they will take a cheap toothbrush, dip it in the paint mixture and scrub the tooth bright and shiny.
Give children a piece of paper suitable to work for painting. Draw a big smile on the paper with marker. Pour different colored paints in small containers and give each child a toothbrush. Have them use a toothbrush to go up and down and to the side to brush the teeth and make an abstract painting.
Combine 1/2 teaspoon salt, 1 teaspoon water, 4 1/2 teaspoons baking soda and 1 drop food coloring (any color) in a sealable plastic bag. Have the kids squish the bag to mix the ingredients then dip a toothbrush in and brush their teeth. Add a drop or two of mint or orange flavoring if desired.
Explain that the toothbrush was invented about 500 years ago and toothpaste 100 years ago. Before that ancient people used what they had around to brush their teeth. They rubbed sage leaves on their teeth or rubbed powdered chalk or charcoal on them. They might swish their mouths with lemon juice or use ashes from the fireplace and rinse really well. Sometimes they even chewed tobacco with honey in it. The only safe option for activity is to use the sage leaf. Give each child a fresh one and let them rub their teeth with it to see how it works and tastes.