If your child is fussy about brushing their teeth is can be that they do not care for the taste of the toothpaste in use. There are many kid friendly toothpaste that may make your child want to brush or brush longer.  Colgate has Colgate Kids in strawberry as well as watermelon flavors. 

Crest toothpaste offers a bubblegum flavor. There are other toothpaste that taste like ice cream.  These flavor toothpaste may help making brushing their teeth much easier. However keep in mind that like any other toothpaste they are to still be kept out of reach of small children and use only for brushing their teeth and not for eating.