Use drawing activities to engage your students in the subject of dental care. Give them all some drawing paper and crayons. Tell them to draw a picture of all the things they need to take care of their teeth, such as toothpaste, a toothbrush and a box of dental floss. They could then draw a picture of someone using these things to clean his teeth.
Have your kids put on a simple classroom production about taking care of their teeth. Help them make costumes out of cardboard boxes that you then paint to look like teeth. Each child will say a line in the play about teeth, such as, "Smiles should be shiny."
While the kids in your class should be brushing after every meal, they may not be doing it properly. One way to address this is to bring in some toy fake teeth and have them practice with these. Give them each a toothbrush, some toothpaste and a bowl of water; tell them to practice brushing the fake teeth. By doing it this way, you can more easily tell when a child isn't doing it right and help her improve.
Another aspect of proper tooth care is diet and nutrition. To address this, help your students create a display on a table that represents the things that are good and bad for your teeth. Make up a lists of these things and then give each child the task of bringing back one of those things the next day. Of course, they don't actually have to bring in the whole thing. Since an empty can of soda will do fine for representing it as one of the bad things.