Should parents use rewards to get children to brush their teeth?
We would discourage the use of rewards or treats to encourage a child's dental hygiene, for a couple of reasons. First, it can send the wrong message. Hygiene is something kids should be doing as a matter of daily living, not something they're paid to do. Bribing or threatening kids can therefore send the wrong message. There are many reasons we brush our teeth: to keep our teeth healthy, to have a great looking smile, to avoid painful cavities, and so on. These are the real rewards you should focus on, not artificial ones. Plus you'll eventually need to withdraw the rewards, which can cause problems later.
That said, parents are free to try a small reward system for younger children in order to develop the habit, just be sure to emphasize that this has an end date: you're rewarding them to give them extra motivation so that they can get in the habit of brushing their teeth, and set up a specific time frame, such as two or three months, when the rewards will end. Once that happens, they'll be expected to continue the habit on their own.
If you go this route, use some sort of calendar system in which kids get a sticker for each no-fuss brush day, which translates into a small reward at the end of the week. Be sure the reward is meaningful yet modest; the higher the bribe, the more problems you'll have trying to withdraw it later.