Our four year old likes to do what her big sister does, so when we decided to switch her big sister to toothpaste with fluoride, I was hesitant because I didn't think our four year old was ready. However, the transition went rather smoothly. I went out and bought some small cups and Barbie Colgate toothpaste with fluoride. Our girls were so excited. We explained to them that they cannot swallow this toothpaste and they had to spit it out. My husband and I advised them to fill the small cup with water, rinse their mouths and spit. We supervise them while they're brushing and we only put a tiny bit of toothpaste on their toothbrushes to be safe. We brush their teeth every morning and night.
Children under the age of six should be supervised while they're brushing with toothpaste that contains fluoride and they should only use a pea-sized amount. It's very important for children using fluoride toothpaste to spit because swallowing too much of it can have toxic effects on the body.
It's important to reinforce safe brushing habits with your children. Have them brush their teeth and spit, even when they're using the fluoride-free toothpaste. This will make the transition to fluoride toothpaste easier.