What is the appropriate age to allow a child to brush her teeth by herself? My daughter is about to turn three. Is this old enough to allow her to brush her teeth by herself? How long should I watch her brush for? .

Not yet. At three children do not have the dexterity to do an adequate job brushing there own teeth. I usually recommend having a parent do the brushing until about 8 or 9 years old. It is important that every surface of every tooth be cleaned so flossing is also important at this age.
Dr . Dr kaufman has answered wonderfully. I would just like to add that oftentimes our little ones will want to feel they are brushing on their own. I find it works well to let the child brush first the "check" on the job they did while brushing his or her teeth yourself. This is also a great opportunity to check on your child's thoroughness. I also recommend doing this technique to some extent even to age ten or twelve (for boys especially). Slowly backing off and letting them have more and more responsibility in the process. Really. This is a major gift you are giving your child ... Food oral hygiene habits.
A . A general rule of thumb is age 12. Children have good dexterity by that age, but are still young enough to follow directions without giving you grief. Prior to that parents must brush their kids teeth for them. The best way is to let the child brush first, then you repeat making sure you get all the areas they will not be able to clean. As they get older, say around 8, let them brush by themselves in the morning after breakfast and you do it at night to be sure the teeth are clean at bedtime. Discuss this with your child's dentist to be sure their are no specific concerns.
She . She is definitely not old enough to brush her own teeth. A child does not possess the proper manual dexterity until about the age of 7 that will allow her to properly brush her teeth. However, she definitely is it at the right age to develop good oral hygiene habits. Make sure to get into the habit of brushing after breakfast and before school, and after dinner prior to going to sleep. Brush her teeth thoroughly yourself, then allow her to repeat after you. Consult with your pediatric dentist on proper brushing technique. Remember that's extensive dental work resulting from bad oral hygiene, can cost easily as much as college tuition. Give your child is a head start on life.