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The biology behind braces and aligners, and why steady, gentle force beats hurry.
Teeth move because bone reshapes itself. A gentle, steady push on a tooth tells the bone on one side to make way and the bone on the other side to fill in behind. That is a slow biological process, not a mechanical one, and it is why treatment is measured in months rather than weeks.
A healthy tooth moves about a millimetre a month under light force. Pushing harder does not make it faster; it can make it slower.
Braces work between visits, around the clock. Appointments adjust the direction; the time in between does the moving.
After teeth stop moving, the bone and the fibres around them take a year or more to settle. That is what retainers protect.
Braces and aligners are both just ways of applying a small, constant force to a tooth in a chosen direction. The tooth itself does nothing clever; the bone around it responds. On the side the tooth is moving towards, cells remove a little bone. On the side it is leaving, new bone is laid down. The tooth drifts through the jaw a fraction at a time.
Because the process is biological, it runs at the speed your body sets. Age, general health, and how well the teeth and gums are kept during treatment all play a part.
Heavy force does not speed things up. It can damage the root or the bone, and the tooth can stall. Light, continuous force is what works, which is why the wear rules for aligners and elastics are so specific: force that is on and off achieves less than force that is simply on.
Some stages look slow from the outside. Levelling and rotating teeth early on shows quickly; closing spaces and fine-tuning the bite later on is smaller work that takes just as long.
The plan sets the direction. The hours set the pace.
Last reviewed August 2026