Can Invisalign Fix Crooked Teeth? Who It Helps, Its Limits, and When Braces May Fit Better

Short answer

• Clear aligners, including the Invisalign system, can fix many crooked teeth. The American Association of Orthodontists (AAO) lists crooked, crowded, and gapped teeth among the conditions aligners commonly treat, along with many overbites, underbites, crossbites, and open bites. Each aligner is typically worn for about one week, at least 22 hours a day, and moves teeth a fraction of a millimeter at a time, and aligners are removed for eating, drinking anything other than water, and brushing and flossing. Peer-reviewed research sets the limits: aligners align and level teeth well, but extrusion, which is moving a tooth outward from the gum, was the least accurate movement in a major systematic review, followed by rotation, especially of rounded teeth, and a comparison with fixed braces found braces more effective for producing good bite contacts and controlling root torque. Severe crowding, severe malocclusion, significant rotations, and large gaps may therefore be treated more predictably with braces, sometimes combined with aligners, and very short teeth are a separate problem, because a tray needs enough tooth surface to grip. After treatment, a retainer is needed, because teeth tend to drift back without one.

By Emma Hudson

Yes, in many cases, but not in every case. That short version is the honest answer to the question in the title, and the rest of this article explains where the line falls. Invisalign is the best-known brand of clear aligner: a series of removable, custom-made clear plastic trays that move teeth gradually, in small planned steps. Aligners handle mild to moderate crowding, spacing, and minor bite problems well. They are less predictable for severe rotations, teeth that need to move up or down a long way, large gaps, complex bite corrections, and teeth too short for a tray to grip. Which side of that line a particular smile falls on cannot be judged from a mirror or a photograph. It is decided by an orthodontist or a dentist trained in aligner treatment, after an examination with records such as X-rays, photographs, and digital scans. This article is general information only. It does not diagnose any individual case and it does not replace that assessment.

What Invisalign is and how it works

Invisalign is one brand of clear aligner, made by Align Technology. Other clear aligner systems exist, and the mechanics described here apply to clear aligner treatment generally. An aligner is a thin, clear, plastic-like shell that snaps over the teeth. A treatment is a series of shells, each shaped very slightly closer to the planned final position than the one before, so wearing the sets in order applies gentle, continuous pressure and repositions teeth a fraction of a millimeter at a time.

The AAO describes the usual rhythm clearly: each aligner is typically worn for one week, at least 22 hours a day, although some guidance and some plans use one to two weeks per set and 20 to 22 hours a day, always as prescribed. Aligners come out for eating, for drinking anything other than water, and for brushing and flossing. That removability is the central trade-off: it makes eating unrestricted and cleaning straightforward, and it also means the appliance only works while it is in the mouth.

Treatment starts well before the first tray. The AAO explains that the orthodontist first checks the teeth and jaws using X-rays, photographs, and digital scans, makes a diagnosis, and then designs the plan, detailing which tooth moves where and in what order. The aim is a healthy bite across the whole mouth, not only straighter front teeth. The American Dental Association (ADA), in its MouthHealthy patient guidance, makes the same point about orthodontics generally: treatment is used to correct bad bites, or malocclusion, where teeth are crowded or crooked or the jaws do not meet properly, and removable aligners are one option under the direct supervision of a dentist or orthodontist.

Fixed braces work differently. Small brackets are cemented to the teeth and connected by a wire that is periodically adjusted, so the appliance stays on and works around the clock. Braces can pull, rotate, and upright teeth through the bracket and wire in ways a removable tray, which pushes by wrapping around the crowns, cannot copy exactly. That mechanical difference, not appearance, explains most of the limits covered below.

Why two similar smiles can get different advice

Crooked is a description, not a diagnosis. Two people whose front teeth look equally overlapped may need quite different movements underneath. One may need teeth tipped slightly into line, which aligners do readily. The other may need a rounded tooth rotated a long way, a tooth brought down into the arch, roots uprighted, and a bite corrected at the same time, which is a much harder program.

That is why responsible assessment looks at more than the smile: the type and severity of crowding or spacing, how the upper and lower teeth meet, jaw relationship and, in younger patients, jaw growth, the shape and height of each tooth, gum and bone health, and any decay or gum disease needing treatment first. NHS orthodontic guidance adds that treatment should not begin unless oral hygiene is good, because treatment can increase the risk of tooth decay and gum problems.

Families weighing this question for a teenager have a companion guide on this site: our article on Invisalign for teens, written for parents, covers eruption, growth, school-day wear, and the questions to ask when the patient is still growing.

The movements aligners handle well

Aligners are at their best aligning and leveling the arches in mild to moderate cases. The systematic review by Rossini and colleagues, published in The Angle Orthodontist in 2015, concluded that clear aligner treatment aligns and levels the arches, is effective in controlling anterior intrusion, which is pressing front teeth slightly back into the gum, and posterior side-to-side inclination, and is effective in controlling upper molar bodily movement of about 1.5 millimeters, with the highest predictability in that review, at 88 percent, for upper molar distalization of at least that amount. In everyday terms, the reliable territory includes:

• Mild to moderate crowding, where overlapped teeth need to be tipped and shuffled into line.
• Spacing and small to moderate gaps, where teeth need to be drawn together in a controlled sequence.
• A single crooked front tooth or mildly crooked lower front teeth, where the movement needed is mainly tipping or a small rotation and the tooth offers a good surface for the tray to grip.
• Mild bite problems, including some overbites, underbites, crossbites, and open bites, in the forms the AAO lists as commonly treated with aligners.
• Relapse after earlier orthodontic treatment, where teeth have drifted modestly, provided retention is then taken seriously.

A 2025 expert consensus in the International Journal of Oral Science gives a similar pattern, rating molar distalization and expansion as the more predictable movements.

The movements aligners handle poorly

The same evidence is candid about the weak spots, and readers should weigh these more heavily than any general claim that aligners can fix everything.

Extrusion is the hardest movement. Rossini and colleagues found extrusion was the most difficult movement to control, at about 30 percent accuracy, meaning only about a third of the planned outward movement was achieved on average in the studies reviewed. Rotation came next, and the review concluded that aligner treatment is not effective in controlling rotation of rounded teeth in particular. Rounded teeth, such as canines and some premolars, give a smooth tray little to push against, so the tooth can slip inside the tray instead of turning. The 2025 expert consensus reaches a consistent conclusion, rating extrusion at about 30 percent predictability, with rotation and torque control also limited.

Torque and bite contacts are the other consistent gap. Ke, Zhu, and Zhu, in a 2019 systematic review in BMC Oral Health comparing aligners with fixed appliances across eight studies, concluded that both treatments were effective for malocclusion, but that aligners were not as effective as braces in producing adequate occlusal contacts, which is how well the upper and lower teeth meet, in controlling tooth torque, which is the tilt of the root as well as the crown, or in increasing transverse width and retention outcomes. Their finding of shorter aligner treatment duration in the included studies should not be read as a promise for an individual case.

The AAO summarizes the practical consequence: clear aligners may not work as predictably for severe malocclusions, significant tooth rotations, and large gaps, and traditional braces may offer more precision in those cases. Aligners are a real orthodontic appliance with real limits, not a cosmetic cover and not a universal substitute for braces.

Who aligners help most, and who they may not

Aligners tend to help most when crowding or spacing is mild to moderate, the bite problem is minor or mainly about tooth position rather than jaw position, the teeth offer enough height and surface for a tray to grip, permanent teeth are mostly in place, gums are healthy, and the patient will genuinely wear the trays as prescribed, every day, for months. They may be a poor fit when crowding is severe, several teeth need large movements in different directions, a tooth needs major vertical movement, the bite discrepancy is large or skeletal, teeth are very short, worn, or partly erupted, or a removable appliance will spend too much time in its case. The 2025 expert consensus states two of those points directly: clear aligners are not recommended for patients with clinically short crowns or poor compliance.

Can aligners fix very crooked teeth?

Sometimes, with help, and sometimes not predictably. Experienced orthodontists treat some complex cases with aligners by staging movements carefully, adding attachments and elastics, planning extra space, and accepting additional refinement stages. Other cases are treated in stages, with braces for the hardest movements and aligners for part of the program. The AAO notes that aligners can be paired with orthodontic elastics, that some cases are treated more predictably with braces, and that an orthodontist may recommend aligners, braces, or a combination.

Treat with caution any blanket claim that aligners can fix every crooked smile, or a plan offered without an in-person examination, records, and a discussion of limits.

Short teeth, grip, and why tooth shape matters

Aligners move teeth by wrapping around the visible part of the tooth, called the clinical crown. A tooth that is very short, heavily worn, small and pointed, or only partly erupted gives the tray little surface to hold and little leverage to apply a turning or lifting force. The tray can slide, fail to seat fully, or deliver tipping when the plan needed something more controlled.

Attachments can help, within limits. They are small, tooth-colored shapes of dental composite bonded to selected teeth for the course of treatment. The AAO explains that tooth-colored attachments are frequently placed to help aligners guide teeth into place. An attachment gives the tray a ledge to push against, which can improve grip and help with rotations. Attachments are removed at the end of treatment. They do not turn a very short tooth into a long one, and the expert consensus position is that clinically short crowns remain a reason to steer away from aligners. If you have short teeth, ask specifically about grip, about which teeth would carry attachments, and whether braces, which bond a bracket directly to the tooth, would control those teeth more reliably.

Attachments, elastics, and interproximal reduction

Three additions extend what an aligner plan can attempt. Attachments improve how force is applied, as described above, and are common rather than a sign that a case has gone wrong. Elastics are small orthodontic rubber bands worn between the upper and lower teeth, hooked to attachments, buttons, or cutouts in the trays, to help correct how the bite meets, something a tray acting on one arch alone cannot do. Like the trays, they only work while worn.

Interproximal reduction, often shortened to IPR, is the planned removal of a very small amount of enamel from the sides of teeth where they touch, to create space for crowded teeth to move into line. It is irreversible, so it should be explained in quantity and purpose before it is done. A systematic review by Gomez-Aguirre and colleagues (2022) found no enamel demineralization, no increase in caries incidence, no periodontal changes, and no dental sensitivity after IPR in the studies included, while grading the overall quality of that evidence as low to very low. The balanced reading is that IPR is an established technique with reassuring but thin safety evidence, not a step to accept without a clear explanation. None of these additions makes extrusion or a large rotation of a rounded tooth as predictable as braces can make it.

Compliance: the 22-hour rule is the treatment

No section of this article matters more in daily life. The AAO puts the requirement at at least 22 hours a day on its aligner page, and at 20 to 22 hours a day in its aligner therapy guidance, in both cases as prescribed. In practice that leaves roughly two hours a day for all meals, snacks, drinks other than water, and cleaning combined. A tray in a case, in a napkin, or on a desk applies no force at all, and teeth under-treated day after day do not arrive at the position the next tray was built for. The result is called poor tracking: the aligner stops seating fully, progress stalls, treatment lengthens, and extra stages may be needed.

Honest self-assessment before treatment is therefore part of candidacy. Frequent snacking makes aligner life harder, because every snack restarts a remove, eat, clean, and replace cycle. Readers who graze through the working day may find our guide to hydration and healthy snack swaps for workdays useful for the same reason it helps here: fewer, planned eating occasions are easier to manage around an appliance. The AAO warns specifically against drinking soft drinks, flavored waters, or sports drinks with aligners in, because liquid seeps under the tray and, if it contains acid, sugar, or both, can rapidly stain teeth and cause extensive decay. Water is the only drink to have with trays in.

Discomfort is the other common reason trays stay out. A new set usually feels tight, because it is shaped a step ahead of the teeth, and mild pressure for a few days after a change is the normal pattern described by the AAO. Severe pain, a sharp edge, a tray that will not seat, a cracked tray, or a bite that suddenly feels very wrong are different: contact the treating office promptly. Short-lived sensitivity is also common when teeth are moving, and our article on sensitive teeth and cold food explains which patterns are ordinary and which deserve a prompt appointment.

Refinements: extra aligners are normal, not a failure

Because aligners do not achieve every planned movement exactly, many treatments include refinements: a fresh scan partway through or near the end, followed by an additional series of trays to finish movements that fell short. A survey study published in Dental Press Journal of Orthodontics, in which 188 orthodontists reported on their own aligner cases, found that at least one refinement was requested in 70.31 percent of cases, and a second refinement in 21.95 percent. More experienced specialists requested refinements more often, which supports reading them as a normal finishing tool rather than a mistake.

Ask at the start whether refinements are expected and included in the quoted fee. A plan that presents the first series of trays as a guaranteed finish, with no mention of refinements, is less honest than a plan that builds them in.

Protruding teeth, overbite, and the limits of moving teeth

Protruding upper front teeth, often called buck teeth, illustrate the difference between a tooth position problem and a jaw position problem. When protrusion is mild and mainly about the angle and position of the front teeth, aligners may be able to tip and retract those teeth, sometimes helped by IPR or by moving molars back in sequence. When protrusion reflects the relationship of the jaws, or a large overbite with a deep bite, treatment is more complex. Aligners move teeth. They do not change jaw growth or facial structure on their own, and a growing patient with a skeletal problem may need growth guidance, braces, elastics, or, in severe adult cases, a combined orthodontic and surgical discussion.

Poorly planned treatment, or trays worn inconsistently so that some teeth move and others do not, can also leave a bite feeling uneven. That is an argument for supervised treatment with regular checks, and for reporting a bite that feels wrong promptly.

Aligners compared with braces

The AAO publishes a side-by-side comparison of braces and aligners, and the table below follows it closely, with the evidence limits from the reviews above added to the final row.

The AAO’s central point is that one appliance is not inherently better than another. What matters is the diagnosis, the goals of treatment, and the patient’s lifestyle and habits. For some adults, being able to speak and present at work without a visible appliance is a genuine reason to choose aligners, and our guide to how to build confidence in public speaking covers the wider confidence side of that concern. Appearance is a legitimate factor, to sit alongside, not instead of, the movement evidence above.

Oral health during aligner treatment

Straightening teeth can make some crowded areas easier to clean, and aligners have one real hygiene advantage over braces: they come out, so brushing and flossing follow the normal routine. The ADA’s MouthHealthy guidance lists tooth decay, gum disease, tooth loss, affected speech or chewing, abnormal enamel wear, and jaw problems among the possible consequences of leaving an abnormal bite uncorrected. Those are reasons to treat a genuine malocclusion, not a guarantee that straightening alone prevents decay.

Aligners also create their own hygiene risks. A tray worn over unbrushed teeth traps food, plaque, and sugary liquid against the enamel for hours. The AAO warns that aligners can trap liquids and food particles against the teeth, increasing the risk of cavities and gum disease, and that teeth need to be spotless when aligners go back in. White marks, an early sign of enamel demineralization, are a recognized risk in orthodontic treatment generally. The practical routine is unglamorous: brush after eating before trays go back in, clean the trays as instructed, drink only water with trays in, and keep regular dental checkups running alongside orthodontic visits, as our guide to how often you should go to the dentist explains. Bleeding or swollen gums during treatment should not be ignored; our article on the signs of gum disease sets out the warning signs that need a dental appointment in their own right.

Retention: the part that keeps teeth straight

Finishing the last aligner is not the end of treatment. Without a retention phase, teeth tend to return toward their original positions, a process called relapse. The Cochrane systematic review of retention procedures, updated in 2023 and covering 47 studies with 4,377 participants, states that background plainly: without retention there is a tendency for teeth to relapse, and almost every person who has orthodontic treatment will require some type of retention. The same review is honest that the evidence comparing retainer types is low to very low certainty, so no single retainer type or wear pattern can be presented as proven best.

Retainers are either removable, including clear plastic retainers that resemble a passive aligner, or fixed, typically a thin wire bonded behind the front teeth. NHS orthodontic guidance explains that retainers hold teeth in place while the surrounding gum and bone adjust, that tooth position can continue to change throughout life, and that some movement is likely if a retainer is stopped. Wear the retainer exactly as advised, for as long as advised, which is commonly long-term and often indefinite part-time wear, and report a lost, broken, or no longer fitting retainer promptly. Budgeting for retainers and their replacement is part of the real cost of straight teeth.

Questions to ask before starting

• Is my case mild, moderate, or complex, and which specific movements does it need?
• Which of those movements do aligners do least predictably, in my case?
• Would braces, or a combination of braces and aligners, give a more predictable result, and why?
• Are my teeth tall enough for a tray to grip, and will I need attachments?
• Will I need elastics, or interproximal reduction, and if IPR is planned, how much enamel, from which teeth, and for what space?
• How many hours a day must I wear the aligners, how many sets are planned, and how often will progress be checked?
• Are refinements expected, how many rounds are included in the fee, and what happens if a tooth does not track?
• What will treatment cost in total, including refinements, replacement trays, retainers, and retainer replacement?
• What is the retainer plan afterwards, what type, worn how often, and for how long?
• What should I do, and who should I contact, if a tray is lost, cracks, or stops fitting, or if my bite starts to feel wrong?

Clear, specific answers, tied to your own examination, are the sign of a careful assessment.

Frequently Asked Questions

Can Invisalign fix a crooked front tooth?

Often yes, if the movement needed is mild to moderate, mainly tipping or a small rotation, and the tooth is tall enough for the aligner to grip, helped where needed by an attachment. A severe rotation, a tooth that needs to move a long way up or down, or a front tooth in a complex bite may need braces or a combined approach.

Can I get Invisalign if my teeth are really crooked?

It depends on the type of crookedness, not only on how crooked the teeth look. Severe crowding, large rotations, major vertical movements, and complex bite problems are the cases where the evidence and the AAO both say braces may be more predictable. Some complex cases are still treated with aligners using attachments, elastics, space creation, and refinements, but that judgment belongs to the orthodontist who has examined you.

Can Invisalign fix short teeth?

Short teeth are difficult for aligners, because the tray needs enough tooth surface to grip. Attachments can improve grip in some cases. The 2025 expert consensus lists clinically short crowns as a reason aligners are not recommended, so braces, which bond directly to the tooth, may be better where teeth are very short, worn, or partly erupted.

Will Invisalign work if I do not wear it enough?

Not as planned. Aligners only move teeth while worn, and AAO guidance is at least 22 hours a day, or 20 to 22 hours as prescribed. Persistent under wear leads to poor tracking, longer treatment, extra refinements, or a compromised result. If you cannot sustain that wear pattern, say so before treatment: braces do not depend on it.

Does Invisalign give perfect teeth?

No treatment can guarantee perfect teeth. Aligners can improve alignment and, in suitable cases, the bite, but results depend on the starting position, the movements needed, wear time, oral health, and retention. Aligners also do not change tooth shape, size, or color.

Do I need a retainer after Invisalign?

Yes. Teeth tend to drift back after any orthodontic treatment, and the Cochrane review of retention concludes that almost everyone treated needs some form of retention. Your clinician will advise a removable retainer, a fixed wire retainer, or both, and for how long, which is commonly long-term part-time wear.

Sources & references

• American Association of Orthodontists (AAO), Clear Aligners: Discreet Ways to Straighten Teeth, aaoinfo.org. Aligners as clear trays applying gentle pressure; each aligner typically worn for one week, at least 22 hours a day, moving teeth a fraction of a millimeter at a time; removal for eating, drinking, and brushing and flossing; conditions commonly treated, including crooked, crowded, and gapped teeth, overbite, underbite, open bite, and crossbite; aligners not right for everyone, with some cases treated more predictably with braces or a combination.
• American Association of Orthodontists (AAO), Clear Aligner Therapy: The Discreet Way to Straighten Teeth, aaoinfo.org. Wear of 20 to 22 hours a day as prescribed; assessment with X-rays, photos, and digital scans before planning; attachments; limits for severe malocclusions, significant tooth rotations, and large gaps, where braces may offer more precision; compliance as a condition of success; risk of cavities and gum disease when liquids and food are trapped against the teeth.
• American Association of Orthodontists (AAO), Aligners vs. Braces: A Comparison, aaoinfo.org. No single right way and no appliance inherently better than another; diagnosis from orthodontic records as the starting point; side-by-side comparison of visibility, removability, diet, hygiene, discomfort, and treatment scope; retainers needed by all patients after treatment; teeth must be spotless before aligners are replaced; sugary and acidic drinks with aligners in can rapidly stain teeth and cause extensive decay.
• American Dental Association (ADA), MouthHealthy, Braces, mouthhealthy.org. Braces and orthodontic treatment used to correct bad bites, or malocclusion, where teeth are crowded or crooked or jaws do not meet properly; possible consequences of an uncorrected abnormal bite, including tooth decay, gum disease, tooth loss, affected speech or chewing, abnormal enamel wear, and jaw problems; brackets and wire described; removable aligners as an option under the direct supervision of a dentist or orthodontist; treatment of one to three years for most people, followed by a retainer period; healthy teeth can be treated at any age.
• NHS 111 Wales, Orthodontics, adapted from NHS UK content, 111.wales.nhs.uk. Orthodontic treatment improves the appearance and alignment of crooked, protruding, or crowded teeth and corrects bite problems; assessment with X-rays, models, and photographs; treatment not begun unless oral hygiene is good, because treatment can increase the risk of tooth decay and gum problems; retainers hold straightened teeth while gum and bone adjust, can be removable or a thin wire fixed behind the teeth, and tooth movement is likely if a retainer is stopped, with position changes continuing throughout life.
• University of Iowa College of Dentistry and Dental Clinics, Traditional Braces vs. Invisalign: What the ADA and NIH Say, dentistry.uiowa.edu. University dental school summary drawing on ADA and National Institutes of Health material: braces offer precise control including vertical shifts and rotation, which can be challenging with clear aligners, and work continuously without relying on patient compliance; aligners must be worn 20 to 22 hours a day, are removable for eating and cleaning, and may not be suitable for severe rotations, vertical movements, or complex bite corrections; aligners replaced every one to two weeks in that summary.
• Rossini, G., Parrini, S., Castroflorio, T., Deregibus, A., and Debernardi, C. L., Efficacy of clear aligners in controlling orthodontic tooth movement: a systematic review, The Angle Orthodontist, 2015, 85(5), 881 to 889, PubMed PMID 25412265. Eleven studies: aligners align and level the arches, control anterior intrusion and posterior inclination, and control upper molar bodily movement of about 1.5 millimeters, with upper molar distalization the most predictable movement at 88 percent; extrusion the most difficult movement at about 30 percent accuracy, followed by rotation, with rotation of rounded teeth not effectively controlled; conclusions to be read with caution because of the number, quality, and heterogeneity of the studies.
• Ke, Y., Zhu, Y., and Zhu, M., A comparison of treatment effectiveness between clear aligner and fixed appliance therapies, BMC Oral Health, 2019, 19, 24. Eight studies, two randomized trials and six cohort studies: both aligners and braces effective for malocclusion; aligners not as effective as braces for producing adequate occlusal contacts, controlling tooth torque, increasing transverse width, and retention; aligner treatment duration shorter in the included studies, which is not an individual promise.
• Wang, Y., Long, H., Zhao, Z., and colleagues, Expert consensus on the clinical strategies for orthodontic treatment with clear aligners, International Journal of Oral Science, 2025, 17, 19. Expert consensus: aligners provide a pushing force through elastic material covering the clinical crowns, with efficiency varying by movement type; predictability rated highest for molar distalization and expansion and lowest for extrusion, with torque and rotation also limited; aligners not recommended for patients with clinically short crowns, extensive posterior mesial movement needs, or poor compliance; attachments recommended to enhance grip, including for short crowns and complex movements.
• Gomez-Aguirre, J. N., Argueta-Figueroa, L., Castro-Gutierrez, M. E. M., and Torres-Rosas, R., Effects of interproximal enamel reduction techniques used for orthodontics: a systematic review, Orthodontics and Craniofacial Research, 2022, 25(3), 304 to 319, PubMed PMID 34865310. Eight clinical studies: no enamel demineralization, no increase in caries incidence, no periodontal changes, and no dental sensitivity found after interproximal reduction, with overall evidence quality graded low to very low and better trials called for.
• Ladewig, N. M., and colleagues, Does the need for refinement sets of orthodontic clear aligners correlate with professional experience?, Dental Press Journal of Orthodontics, SciELO. Survey of 188 orthodontists: at least one refinement requested in 70.31 percent of aligner cases and a second refinement in 21.95 percent; mild and moderate crowding the most indicated malocclusions, and extraction and presurgical treatments the least.
• Martin, C., Littlewood, S. J., Millett, D. T., and colleagues, Retention procedures for stabilising tooth position after treatment with orthodontic braces, Cochrane Database of Systematic Reviews, 2023, CD002283, PubMed PMID 37219527, PMCID PMC10202160. Forty-seven studies with 4,377 participants, in patients treated with braces: without a retention phase, teeth tend to relapse to their initial position, and almost every person treated will require some type of retention; evidence comparing retainer types and strategies is low to very low certainty, so no single approach can be presented as proven best.