Orthodontic treatment can be completed in as short as 6 months for very minor tooth movements or it can take up to 2 years for more complex treatments. Most cases will generally take 12 to 18 months for the teeth to line up neatly. It all depends on whether the teeth were very crowded to begin with or just a little. Teeth can start to move quite quickly and with Invisalign type braces you will move to the next aligner every 1-2 weeks. With fixed braces you will need to see the orthodontist every 6 -8 weeks.