In order to get the best results from brushing your teeth a person need to brush for at least two to three minutes. Even though most people will state they brush three to four on average a person brushes their teeth less then a minute.
Most people are not really timing themselves so what feels like two to three minutes is really much shorter. Therefore a good way to make sure you are brushing a full two to three minutes is by brushing to a song. The average song is about three minutes which is the right amount of time to get the best results from brushing.