The main advantage of Invisalign is that it does not hurt like metal braces. Each aligner only moves the teeth .25 millimeters. That small movement is usually done in 1-2 days. It is a controlled, gentle movement. In addition, it is very easy to clean the teeth after eating. The movements are calculated in a computer-generated treatment plan that simulates the movement of the teeth, tells how many aligners you will need and what potential problems you might have.