What clear aligners can and cannot treat

Clear aligners move teeth. In the right case they can straighten crowded teeth, close small gaps and improve many bite problems, often with help from small tooth-coloured bumps called attachments, elastic bands, or a little reshaping between some teeth. They cannot move an adult's jaws, replace a missing tooth, move an implant, or treat decay, gum disease or tooth colour. Whether aligners suit your teeth depends on what is causing the problem and how severe it is, and an in-person examination works that out.

The British Orthodontic Society describes clear aligners as a way of correcting mild to moderate problems, after a full assessment and a discussion of the options. Mild cases are not automatically suitable, and some more complex cases can still be treated after a full examination.

Problem by problem

The table sets out the general pattern in British Orthodontic Society guidance and the research below. It is a guide for the conversation with a dentist or orthodontist, not a self-diagnosis, because the same label can describe a small tooth problem or a large jaw problem.

Some movements are harder for aligners than for fixed braces. A 2019 systematic review comparing the two found aligners less effective at widening the arch, controlling the angle of tooth roots, and getting the back teeth to meet firmly.

Why the cause matters more than the label

An overbite, underbite, crossbite or open bite can come from where the teeth sit, from the size and position of the jaws, or from both.

Aligners work on the first. They move teeth through the bone that holds them, and they leave the jaw bones where they are.

When the problem is mainly in the teeth, aligners can often do the job, sometimes with help:

• Attachments are small pieces of tooth-coloured filling stuck to some teeth so the tray has something to grip.
• Elastics are small bands hooked between the upper and lower teeth to help correct how they meet.
• Reshaping between teeth, which dentists call interproximal reduction or slenderising, removes a thin layer of enamel from the sides of some teeth so crowded teeth have room. The British Orthodontic Society says it can also be used to improve the shape of teeth, and that removing too much enamel can harm the teeth. Gaps are usually closed by moving teeth together rather than by reshaping. Whether your plan needs reshaping or extractions depends on your teeth, so ask.

Fixed braces may also be needed when the crowding is severe, when teeth need to come out, when the movements are complex, or when the jaws differ in size or position. An orthodontist can combine aligners with fixed braces or other methods.

When the jaws are the main cause, the treatment changes: if the jaws are not in the right position, orthodontics alone cannot correct the bite. Surgery moves the jaws, with fixed braces before and after it, and it is usually done once growth has finished. A good assessment will say which kind of problem you have before any trays are made.

How closely teeth follow the plan

Before treatment you are usually shown a digital model of where your teeth should end up. Real teeth often fall short of it. A 2020 study of 38 adults who wore Invisalign as instructed measured how far each tooth moved compared with the movement planned for it. On average, teeth achieved about half of the planned movement, and turning teeth was the least accurate. That measures the accuracy of individual movements, not whether treatment worked: of the 19 finished cases graded against a standard orthodontic score, 14 passed. It is one system in one study, but it shows the plan is a target. Extra trays, called refinements, are a common way of closing the gap, so ask before you start how many are included.

What aligners do not treat

Decay and gum disease. These are checked at the examination and treated before teeth are moved. Teeth can be moved at any age if the teeth and gums are healthy, but decay is a risk if they are not kept clean during treatment. Ordinary dental check-ups should continue throughout.

Missing teeth and implants. Where a tooth is missing, there are two different plans. Aligners can sometimes close the space by moving the neighbouring teeth together, in which case no replacement may be needed. Or they can open or hold the space so that a bridge or implant can fill it. Your clinician should say which plan you are on before treatment starts. An existing implant is fused to the bone and does not move, so the plan has to work around it. Crowns, bridges and heavily filled teeth also belong in the examination; ask about them before treatment starts.

Tooth colour and shape. Whitening is a separate treatment. Aligners leave a chipped, worn or pointed tooth in the shape it already has; bonding or veneers are separate treatments.

Keeping the result. Teeth tend to move back, so retainer wear is lifelong. Care after the last aligner is covered in care after clear aligners.

Children and teenagers

The British Orthodontic Society says aligners are ideally suited to adults whose work or daily life makes a fixed brace difficult. A teenager can still be assessed, but growing jaws and teeth that have not come through yet change the assessment. The NHS says braces are often considered once the adult teeth have come through, and that under-18s may be assessed for NHS treatment when a dentist refers them and the problem affects everyday life, such as eating or cleaning. Where NHS treatment is offered, it is usually a fixed brace; clear aligners are not routinely provided on the NHS.

A minimum age on a company's website is a commercial condition. Under-18s with a problem that affects daily life should be assessed for NHS treatment before anyone discusses a private fee.

How private fees are put together is in what clear aligners cost in the UK.

What the examination should tell you

The General Dental Council said on 13 May 2021 that there is no effective substitute for a physical examination when deciding whether direct-to-consumer orthodontic treatment is suitable, and that you should know the name of the dentist responsible and be able to contact them directly. Photos can show what is visible. The examination, and X-rays where needed, cover the teeth, roots, gums and bite.

Questions that make the examination useful:

• Is my problem mainly in the teeth, the jaws, or both?
• Which teeth will the plan move, and which parts of my bite will it leave as they are?
• Will I need attachments, elastics, reshaping between teeth, or fixed braces for part of the treatment?
• Do I have decay, gum disease or dental work that should be dealt with first?
• What happens if my teeth do not follow the trays, and are extra aligners included?
• How long will I wear retainers, and are they included?

How a clinic plan and a remote plan differ is covered in Invisalign and at-home aligners in the UK. If a tray does not fit fully, or pain lasts beyond the first few days, see when clear aligner treatment goes wrong.