The Academy of Pediatric Dentistry (AAPD) as well as the Academy of Pediatrics (AAP) have changed their recommendations on when to introduce fluoride toothpaste to the general population of children. Fluoride toothpaste is now recommended for use in children as soon as their first tooth comes in. The important thing to note is the amount by which to use. The following amounts of fluoride toothpaste are recommended for use in children, no more than twice daily.
This daily exposure of topical fluoride has shown to significantly decrease the incidence of cavities occurring in young children, with very little risk of developing fluorosis (a cosmetic condition affecting adult teeth, caused by overexposure to ingested fluoride during early childhood).
If a rice grain of fluoride toothpaste is not enough for you to obtain a proper brushing for your child, I would recommend supplementing the toothbrush with a fluoride-free toothpaste, prior to brushing.
For more detailed information on the use of fluoride toothpaste for children, please go to the Academy websites at www.aapd.org or www.aap.org.