How Orthodontics Works UK

How do teeth actually move?

Each tooth sits in a socket of bone, held in place by a periodontal ligament wrapped around its root. When a gentle, sustained force is applied to a tooth — from a wire, a bracket, or an aligner tray — that ligament is compressed on one side and stretched on the other. This triggers a biological remodelling response: bone-dissolving cells (osteoclasts) clear space on the compressed side while bone-building cells (osteoblasts) lay down new bone on the stretched side. Over days and weeks, the tooth physically migrates through the bone into a new position, with the ligament and surrounding bone rebuilding around it at every stage.

How do fixed braces move teeth?

Fixed braces work by bonding a small bracket to each tooth and threading a shaped archwire through them. The archwire is manufactured with a memory for its ideal shape, so when it is engaged into the brackets on crooked teeth, it constantly applies a gentle spring-like force trying to return to that shape — pulling the teeth with it. Orthodontists change wires through treatment, starting with thin, flexible wires for initial alignment and progressing to thicker, stiffer wires for bite correction and fine detailing. Elastics and additional components add specific forces for movements the wire alone cannot achieve.

How do clear aligners move teeth?

Clear aligners move teeth through a pre-planned series of small incremental steps, with each tray in the series nudging the teeth slightly closer to their final position. Small tooth-coloured attachments bonded to certain teeth act as grip points so the smooth plastic tray can apply more precise or complex forces, and elastics may be added for bite correction. Because each tray only makes a very small movement, aligners rely on wearing each one for the prescribed number of hours daily and progressing through the sequence on schedule; missed wear time means the tray no longer matches the tooth position, causing poor tracking.

Why can't orthodontic treatment be sped up indefinitely?

Biology sets a hard limit on how fast teeth can safely move, because bone remodelling is a living cellular process that takes time regardless of how much force is applied. Using excessive force does not accelerate the process — instead it can cut off blood supply to the ligament, increase the risk of root resorption (permanent shortening of the tooth root), cause more pain and swelling, and in aligner treatment, cause trays to stop fitting properly because the tooth cannot keep pace with the plan. Safe, moderate, sustained force applied consistently is what produces reliable, lasting results.

Why do teeth need retainers after treatment?

When active treatment ends, the bone and ligament around each tooth have only just finished remodelling into the new position and have not yet fully matured or stabilised. Without a retainer holding teeth in place during this consolidation period, the same biological forces that allowed movement during treatment allow teeth to drift back towards their original position, a process called relapse. Retainers — whether a fixed wire bonded behind the teeth or a removable clear tray — apply just enough passive resistance to keep teeth still while the surrounding bone fully consolidates, which is why long-term or indefinite retainer wear is recommended.

Useful related pages

This guide is for general information only. It is not a diagnosis, treatment plan, or substitute for advice from a registered dentist or orthodontist.