The Complete Guide to Clear Aligner Treatment: Suitability, Process, Wear Time and Results
For adults considering clear aligners: what they can and cannot move, planning, attachments and IPR, wear time, tracking, refinements, discomfort, risks, results and the current fee list. The core point: evidence suggests teeth often fall short of some planned positions with the first set of aligners, so tracking problems and refinements are a normal part of treatment. If an aligner stops fitting closely, tell the dental team treating you.
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Clinically reviewed by Dr Ibraheem Ijaz, dentist · GDC 301711
Medical disclaimer: This page is for general information only. It does not replace an examination or treatment by a dentist.
Dr Ibraheem Ijaz, principal dentist at Deepcar Dental Care, reviewed this guide. He is a General Dental Practitioner with a BDS, a BSc (Hons), an MSc from Leeds, a PG Dip in Implant Dentistry and a PG Cert in Restorative and Aesthetic Dentistry.
What is clear aligner treatment?
Clear aligner treatment straightens teeth with a series of removable plastic trays, each worn in turn to move the teeth a little further. The British Orthodontic Society (BOS) describes aligners as thin, clear, flexible plastic mouthguards that fit closely over the teeth. Working through the series, each appliance shifts the teeth a short way towards their planned position until the final result is reached.
This guide covers what aligners can move, how the plan is made, attachments and interproximal reduction (IPR), wear time, tracking, refinements, discomfort, risks and results. It draws on guidance from BOS and the General Dental Council (GDC) and on published research, and most topics point to a page that goes deeper.
BOS sees aligners as a good fit for adults whose work or lifestyle makes more visible fixed braces hard to wear.
Aligners are custom-made from plastic, and the specific materials have a page of their own: the materials aligners are made from.
At Deepcar Dental Care, the aligner package includes the consultation, the scan and digital plan, and all the aligners; other items in the package are listed on the main clear aligner page, which covers straightening teeth with removable aligners. Smartee clear aligners are the system used at the practice.
What can clear aligners move, and what can they not?
Clear aligners correct mild to moderate orthodontic problems, according to BOS, once a full assessment and a discussion of the options have taken place. They are most often used where the teeth need aligning without extractions.
BOS counts dental irregularity that is mild to moderate, mild spacing, and crowding that can be resolved by mildly to moderately widening the dental arch or by slimming the sides of the teeth among routine aligner treatments. Its examples of when aligner treatment may need extra techniques, such as fixed braces, to reach an ideal result are severe crowding, treatment needing extractions, complicated tooth movements, and problems arising from a mismatch between the jaws in size or position.
Some tooth movements are harder for aligners than others. A 2015 systematic review of 11 studies with 480 patients, in which the aligners all came from one system, said the quality of the studies was not sufficient to draw any evidence-based conclusions. With that warning, it concluded that aligners can align and level the arches in people who have stopped growing, but are not effective in controlling extrusion of the front teeth (moving them further out of the gum) or rotation, of rounded teeth in particular.
Extrusion was the least accurate movement, at 30% in the one study behind that figure, with 0.56 mm attempted on average, in treatment that ended without a finishing or refinement phase. The review added that aligner treatment relies on extras such as attachments, elastics and IPR to make tooth movement more predictable.
A 2026 narrative review, written by one author with no formal grading of its studies, explains part of why some movements are less predictable. Digital planning systems mainly use models that assume tooth movements are linear and standard, while real movement depends on biological processes in the ligament and bone around the roots, with substantial variation from person to person. The review reports lower predictability for torque of the front teeth (tilting a tooth's root), extrusion, intrusion of the front teeth (moving them further into the gum) and rotation of canines and premolars than for tipping a tooth's crown.
Pages on aligners with severe crowding, bite problems, gum disease and decay, and existing crowns, veneers or implants sit among the options in this section.
At Deepcar Dental Care, clear aligner treatment is for adults only. The problems treated include mild to moderate crowding and spacing, and bite correction. Complex and extraction cases are assessed case by case; some need braces or a combined approach.
How is clear aligner treatment planned, and what are its stages?
Clear aligner treatment follows a plan made before treatment starts, and the aligners are custom-made to it, BOS explains.
BOS says that, as with any orthodontic treatment, a proper orthodontic assessment, diagnosis and treatment plan is essential to successful aligner treatment.
As general guidance, the plan starts from a digital scan of the teeth. A 3D treatment plan is made from the scan, you are shown a simulation of how the teeth are planned to move, and the aligners are produced to match it. Your consultation confirms how your own plan is made.
In broad terms, the main stages of aligner treatment include these four. The table sets each one out as general guidance; your plan confirms the steps for your teeth.
| Stage | What happens, in general |
|---|---|
| Assessment | An assessment and diagnosis come before any plan is made |
| Scan and plan | A digital scan is used to make a 3D plan of the tooth movement |
| Aligner series | Each aligner moves the teeth a short way before the next takes over |
| Refinement | Further aligners can be planned if teeth have not reached their planned positions |
Pages on the scan and plan, attachments, IPR, refinements and wear time make up the treatment process section: browse this section.
What are attachments and interproximal reduction for?
Attachments are small composite shapes bonded to the teeth to help aligners grip and move them. Interproximal reduction (IPR) makes space by thinning the enamel on the sides of teeth.
In a 2023 systematic review covering 26 studies, 19 of them laboratory or computer simulation studies and seven in people, the authors concluded that attachments significantly improve tooth movement and the retention, or hold, of the aligners on the teeth. They cautioned that computer simulations give only a general description of what happens, not exact values.
A 2022 systematic review of five clinical studies in adults, all at medium risk of bias and only two randomised, concluded that attachments can improve root torque of the front teeth but may not be enough to control it, and that adding them to more teeth can improve the anchorage of the back teeth. Results for rotation conflicted: of three studies, two found no significant difference with attachments and one gave mixed results.
Attachments could increase movement of the molars along the arch, though that gain may not be clinically significant. Attachments also seem to improve intrusion, but the review found the evidence for intrusion and extrusion lacking, and it called for further studies.
BOS describes IPR as taking off up to 0.5 mm of enamel at the sides of the teeth, to make room for alignment or to improve the shape of teeth. Because removing too much enamel can damage the health of the teeth, BOS says you should understand fully what is involved before you agree to IPR.
How many hours a day are clear aligners worn?
Clear aligners are worn for most of the day and night: BOS says full time, except at meal times.
At Deepcar Dental Care, aligners are worn 22 hours a day, with a new aligner every 2 weeks. As general guidance, aligners come out for eating and for drinking anything other than water, and your plan confirms the routine for your own aligners.
A 2021 retrospective cohort covered 2,644 adults, mainly from Germany, Switzerland and Austria, who finished treatment successfully with one aligner company and were told to wear each aligner at least 22 hours a day. By their own reports in an app, 45.5% reached that on every aligner, 17.7% fell short on more than three quarters of their aligners, and the rest fell in between. The authors noted that self-reports can be biased and warned against applying the results to other groups of people.
Wear time has its own page in the treatment process section, alongside the pages on attachments, IPR and refinements.
To ask about clear aligner treatment, book online or call 0114 288 2121.
What does it mean when aligners are not tracking?
In general, aligners are not tracking when the teeth fall behind the digital plan, so planned and achieved tooth positions start to differ. A 2026 single-author narrative review describes tracking loss as a gap that develops between the aligner and the tooth, which can build with each new aligner because a poorly fitting aligner delivers less force. If an aligner no longer fits closely over your teeth, tell the dental team treating you.
A 2026 retrospective study of 40 adults with mild to moderate crowding, treated without extractions other than wisdom teeth at one hospital with one aligner system, compared the front-tooth positions planned for the first set of aligners with those achieved before any refinement. Every type of movement measured differed significantly from the plan, and the authors reported an overall accuracy, meaning the share of the planned movement achieved, of 50.3%.
In the upper front teeth, accuracy for individual tooth movements ranged from 24.5% (intrusion of the central incisors) to 74.4% (rotation of the central incisors in one direction). In the lower front teeth, it ranged from 39.2% (extrusion of the central incisors) to over 70% (tipping of the canines and central incisors towards the tongue). The study measured the crowns of the teeth, not the roots.
The authors noted that its retrospective design limited control over compliance and did not account for possible overcorrection or additional aligners, and that updates to the system during the study period mean the results may not fully reflect its latest version. The authors said additional refinements would be advisable to achieve excellent outcomes.
Why are refinements a normal part of aligner treatment?
Refinements are further aligners planned after, or partway through, the first series, when teeth have not reached their planned positions. A 2026 single-author narrative review says the majority of cases need at least one further series of aligners, and that refinement should be expected as an integral part of aligner treatment rather than treated as a failure.
In a survey in Brazil published in 2025, 188 of the 350 clinicians working in orthodontics who were invited gave complete answers about their aligner treatments from the previous 24 months, 2,937 in all. The authors concluded that refinements were needed in most cases. The answers were self-reported, and the authors noted that case complexity, patient compliance and the aligner brand also play a part.
A 2026 systematic review of 20 studies found refinement defined in many different ways. Its evidence suggested that the need for refinement may be associated with more complex problems, extraction treatment, IPR strategies, severe spacing, larger corrections and the limits of particular movements. The review concluded that refinement should be understood as an outcome with many causes rather than one standard finishing step, and called for standard definitions and prospective studies.
Refinements have their own page in the treatment process section, alongside the scan and plan, attachments, IPR and wear time.
Do clear aligners hurt or affect speech?
Some discomfort with clear aligners is expected: as general guidance, mild pressure or soreness for the first few days of a new aligner is normal. If soreness lasts beyond those first days, let the dental team treating you know.
Evidence comparing pain with aligners and fixed braces is weak. A 2023 systematic review of 12 studies, 5 of them randomised trials, pooled five studies that measured pain in the first week. Pain was lower with aligners only on the third and fourth days, with no difference at the other time points, and the review rated this evidence very low quality.
Over longer periods three studies disagreed: one found more pain with fixed braces, one found no significant difference and one found more pain with aligners from the second month to the twelfth. The authors said the results should be interpreted with caution. If pain during aligner treatment worries you, raise it with the team treating you.
Speech can change too. A 2023 systematic review of seven studies with 332 patients, five of the studies at serious risk of bias, rated the evidence low. All seven studies reported that aligners could affect the clarity and delivery of speech, similar to fixed braces. Most patients recovered in 7 to 14 days, while a few took 30 to 60 days. The review concluded that speech difficulties appear likely with aligners but that patients adapt quickly, and advised caution in interpreting the results. If speech changes bother you, mention them to the team treating you.
Day-to-day pages on discomfort, speech, cleaning, eating and lost aligners make up a section that opens by answering what does this section cover?.
What risks does clear aligner treatment carry?
Reported risks of aligner treatment include shortening of the tooth roots and the enamel risk of IPR. Evidence on gum health is uncertain. If you notice changes in your gums or teeth during treatment, tell the dental team treating you.
A 2021 systematic review of 16 studies of treatment without extractions, 12 of them retrospective, measured root shortening of the upper incisors, with reported averages from 0.25 to 1.13 mm. It found no randomised trial on its question and called the lack of good-quality prospective studies a drawback. Nine studies went into its pooled analysis, only three of them with aligners, and the aligner patients were older on average (28 against 17 years).
It concluded that neither aligners nor fixed braces lead to clinically significant root shortening of the upper incisors, which it set at 1 mm, and that the amount did not differ significantly between them, except at one upper lateral incisor, where fixed braces showed significantly more. It found no studies of root shortening in extraction cases with aligners. Ask about this risk before you agree to treatment.
Gum health evidence is weak. A 2026 systematic review of six randomised trials found gum measurements significantly better with aligners than with fixed braces. Five of the trials were at high risk of bias, and the certainty of evidence was low for gum health and very low for oral hygiene. The review concluded that any advantage of aligners for oral hygiene and gum health depends heavily on compliance, and that no firm conclusion could be drawn.
What results can clear aligners achieve?
A 2019 systematic review found clear aligners and fixed braces both effective for malocclusion (misaligned teeth or bite), with braces stronger on several measures. It covered eight studies, two of them randomised trials, comparing one aligner system with fixed braces in 706 people, published from 2005 to 2018. Its finding that both were effective rested on a similar overall score pooled from two studies with very different results, and the authors said that result should be interpreted with caution.
In both of those studies a smaller share of aligner cases reached a passing score: 20.8% against 47.9% in one, a significant difference, and 66.7% against 75% in the other, which was not significant.
The 2019 review concluded that braces were more effective at achieving great improvement, producing adequate contact between the teeth, controlling torque, increasing arch width and retention (keeping the result stable afterwards). Two studies scored great improvement on one index: one favoured braces and the other, with a wider definition, found no significant difference. Two studies measured arch width: in one, braces widened the upper arch more at the canines and premolars but not the molars, and in the other, aligners tended to widen across the lower canines while braces did not.
Retention came from one study of 22 people, where alignment relapsed more with aligners but the overall score did not differ significantly. It also concluded that aligners had an advantage in shorter treatment time, but that result came from patients without extractions, and 3 of the 7 studies in those patients found no significant difference, including the only randomised trial among them.
In one trial of extraction treatment, aligners took 44% longer. The authors noted that aligner technique keeps evolving and that more recent studies reported better aligner outcomes.
How the two appliance types compare for different problems is covered on our page about fixed braces compared with aligners.
What happens after aligner treatment ends is explained in our guide to retention after treatment.
How long does a course of clear aligners take?
How long aligner treatment takes depends, as general guidance, on how far your teeth need to move.
Small front-tooth corrections can take a matter of months, while fuller treatment often takes 12 months or more, and your 3D plan shows the planned length before you commit. Your consultation confirms the expected length for your teeth.
Because a new aligner follows every 2 weeks, the number of aligners in your plan and the length of treatment are linked. The changes in the ligament and bone around the roots that let teeth move are the subject of our page on the biology of tooth movement.
How much does clear aligner treatment cost?
The practice's current fee list, which gives “from” prices, shows this price:
- Clear aligners: from £1,495 per arch
The fee list does not say whether this line covers braces.
Frequently asked questions
How many aligners will you need?
No fixed number applies to everyone. As general guidance, your treatment plan sets the number of aligners, and because a new aligner follows every 2 weeks, more aligners means a longer treatment. The 3D plan shows its planned length before you commit, and any refinements add further aligners to the plan.
What happens to attachments when aligner treatment ends?
In general, attachments are removed. A 2026 systematic review of three laboratory studies found removal appears to be associated with measurable enamel loss and leftover composite, largely depending on the instruments and magnification used. With no clinical trials, it said the findings cannot be applied directly to routine practice. You can ask about this before you agree to treatment.
Why do aligners stop tracking?
Several factors can contribute. A 2026 single-author narrative review groups the causes of inaccurate movement into how people's teeth respond, the limited forces aligners deliver, force lost by the material during wear, and compliance, calling too little wear time one of the most common causes of tracking failures. If an aligner stops fitting closely, tell the dental team treating you.
Do you need an in-person examination before aligner treatment?
Yes, in the GDC's view. Its statement on direct-to-consumer orthodontics says clinical judgements about whether a course of orthodontic treatment suits you must rest on a full assessment of your oral health, and that, for now, nothing effectively replaces a physical, clinical examination as the basis for that assessment.
Can clear aligners widen a narrow arch?
Within limits, and sources differ. BOS calls mild to moderate arch expansion for crowding routine. A 2026 single-author narrative review placed upper-arch widening among the more predictable; a 2026 systematic review listed arch widening among the less predictable. A 2019 review favoured braces on one upper-arch study, though a second study found aligners tended to widen across the lower canines.
Can vibration or laser devices help aligners work?
Not consistently, on current evidence. A 2026 systematic review of seven randomised trials (266 participants), six of vibration devices and one of low-level laser, found no consistent, clinically meaningful benefit from adding them to aligner treatment. Certainty was low to very low, so further well-designed trials are likely to change the estimates.
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