How teeth aligners work

Treatment with Teeth Aligners works in five stages: an assessment with a clinician, impressions of your teeth, a movement plan approved by a clinician, trays made in our own laboratory in Pakistan, then wear and follow up until a retainer holds the result.

• Stage 1, assessment: in person in one of five cities, or by video call from abroad.
• Stage 2, impressions: taken at the clinic, or with an impression kit couriered to you overseas.
• Stage 3, plan: tray by tray movement planned and approved by a clinician, not an algorithm.
• Stage 4, manufacture: models 3D printed, trays thermoformed on USA imported sheet, trimmed and polished by hand.
• Stage 5, wear and retain: a new tray roughly every week, at least 22 hours a day, then about six months of retainer wear.

While you wear an aligner, the tray presses on one side of a tooth, and the bone around its root slowly reshapes in response: bone is removed on the side the tooth is moving towards and laid down on the side it is moving away from. The tooth travels with the bone, a fraction at a time.

Teeth are not fixed rigidly into the jaw. Each root sits in a socket, held by a thin layer of fibres called the periodontal ligament. Light pressure on the tooth is felt through those fibres, and the body responds by remodelling the bone around the root. This is the same process braces rely on.

Two things follow from this. First, the pressure has to be steady: if a tray is out for long periods, the process stalls and the tooth can drift back. Second, the bone needs to be healthy. That is why gums and bone are checked before any straightening starts, and why gum problems are treated first.

Watch the journey

What does the aligner journey look like in practice?

In practice, the aligner journey is a routine: a new tray about every week, the trays out only to eat, drink and brush, and a check on progress along the way. Our video walks through the full journey, step by step.

Most patients say the first two weeks are the adjustment: getting used to the feel, the slight pressure and the habit of brushing before the trays go back in. After that, aligners become part of the day.

You wear aligners about 22 hours a day. They come out only to eat, to drink anything other than plain water, and to brush and floss, and they stay in while you sleep. Two hours a day out of your mouth, in total, is the budget.

The reason is biological. The bone around the roots responds to steady pressure. Wearing trays for twenty two hours keeps that pressure almost constant; wearing them for twelve gives the teeth half the day to start drifting back.

In practice, this means planning meals. Patients who graze all day find aligners hard; patients who eat three meals and a snack find twenty two hours easy. Keep the case with you, take the trays out for the meal, brush, and put them straight back in.

Making space

What is IPR, and why is it done with aligners?

IPR, interproximal reduction, is the careful polishing of a very thin layer of enamel from between some teeth to make room for crowded teeth to line up. It is planned in advance, measured in fractions of a millimetre, and usually done in a few short steps during treatment.

IPR often avoids the need to remove a tooth to create space. It is not painful, because the enamel has no nerves, and the polished surfaces are left smooth. Our video explains when IPR is used and why it helps.

Clear aligners do not usually hurt, but most people feel pressure or mild soreness for a day or two when they start a new tray. That pressure is the tray working, and it fades as the teeth move into the tray's shape.

The first tray is usually the most noticeable, simply because the feeling is new. Many patients switch to a new tray at night, so the first hours of pressure pass while they sleep. Soft food for the first day of a tray helps too.

What is not normal is sharp pain or a tray that cuts the gum. A rough edge can be smoothed in a minute, so tell us rather than putting up with it.

Progress is checked by a clinician at regular points during treatment: in person for patients in Pakistan, and from a clear photo about twelve days into each new tray for overseas patients. The check confirms the teeth are following the plan and the trays are fitting.

A well fitting tray sits flush against every tooth, with no gap at the edges. If a gap appears, the tooth is lagging behind, and catching that early is what keeps treatment on schedule. Chewies, small soft rolls you bite on, help each new tray seat fully; see our guide to using aligner chewies.

Between checks, the routine is yours: wear the tray, change on schedule, keep the trays clean. Tell us straight away if a tray stops fitting, cracks or is lost.

A 3D scan records your teeth with a small handheld camera that builds a digital model in minutes, with no putty in your mouth. Impressions record the same shape by biting into a soft material that sets. Both give an accurate starting point for aligner planning; the scan is quicker and more comfortable.

Our short video on 3D scanning shows how the camera moves around the teeth and how the model appears on screen as it goes. Patients who gag easily usually find scanning far easier than impressions.

For patients who cannot visit, an impression kit can be sent home, with instructions for taking impressions yourself. Whichever method is used, accuracy matters more than anything else at this stage, because every tray in the plan is built on that first record.

Aligner trays are made by printing a physical model of your teeth for each stage of the plan, forming a sheet of clear plastic tightly over each model with heat and pressure, then trimming the tray to follow the gum line and polishing the edges smooth. Every tray is then checked, numbered in wear order and packed.

In our laboratory in Pakistan, the models come from 3D printers and the trays are finished by hand. The trimming line matters more than people think: a tray cut too short grips poorly, and one cut too long rubs the gum.

Because the whole series comes from one case file in one place, a replacement or a refinement tray can be made from the same data without starting again.

Aligners work around most crowns and veneers, but dental implants cannot be moved by aligners or braces, because an implant is fused to the bone. The plan simply moves the natural teeth around an implant, treating it as a fixed point.

Crowns and veneers move with the tooth underneath them. The only difference is that attachments bond less readily to porcelain than to enamel, so the clinician may place them on other teeth or use a different approach.

Tell us about any crowns, veneers, bridges or implants at the assessment. They do not usually rule aligners out, but they do change how the plan is built.

How teeth aligners work depends on the problem being fixed. For crowding, the trays first make space and then line the teeth up; for gaps, they walk the teeth towards each other; for bite problems, they move the teeth of both arches so the upper and lower teeth meet correctly.

Crowding

Space comes first. The plan may widen the arch slightly, tip teeth into better positions or use IPR to create the room each tooth needs, then the trays guide the teeth into line.

Gaps

Teeth are moved towards each other in sequence, and the final trays hold the closed gap while the bone settles. A retainer then keeps it closed.

Rotations

Attachments give the tray something to push against, so the tooth can be turned a little with each tray.

Bite problems

Overbites, crossbites and open bites need both arches planned together. Understanding how teeth aligners work on the bite is why these cases are always assessed in person first: the cause, whether teeth or jaw, decides whether aligners can correct it.

Look after aligner trays by rinsing them every time they come out, brushing them gently each day with a soft brush and cool water, and keeping them in their case whenever they are not in your mouth. Avoid hot water, which can warp the plastic, and coloured or abrasive toothpaste, which can scratch and dull it.

Clean teeth keep trays clean. Brush and floss before putting trays back after a meal, so food and sugar are not held against the teeth for hours. A water flosser helps clean around attachments and between the teeth quickly.

Our short video on cleaning aligners shows a simple five step routine. Each tray is only worn for about a week, so a little daily care keeps it clear and fresh until it is time to change.

Aligners stop working when they are not worn enough, when trays are changed too early, or when a tray is used after it has stopped fitting. All three let the teeth fall behind the plan, and the further behind they fall, the harder it is to catch up.

Not enough wear

Less than about 22 hours a day is the most common reason aligners underperform. The trays move teeth only while they are in.

Changing trays early

Moving to the next tray before the current one has done its work means the new tray does not fit, and the teeth are pushed further than they can follow.

Hot drinks and heat

Very hot drinks, or leaving trays in a hot car, can warp the plastic so it no longer fits the teeth.

Skipping checks

Small problems caught at a check are easy to fix. The same problems found months later can mean refinements or a revised plan.