Invisalign can fix a wide range of orthodontic issues, including crowded teeth, gaps, overbites, underbites, crossbites, and open bites. It works best for mild to moderate cases, though advances in aligner technology have expanded what’s treatable. Most people finish treatment in 9 to 18 months, with some simpler cases wrapping up in as little as 6 months.
Crowded Teeth
Crowding is one of the most common reasons people get Invisalign, and it’s one of the things aligners handle best. Research published in Progress in Orthodontics found that clear aligners resolved 87% of upper arch crowding and 81% of lower arch crowding in patients who started with severe irregularity (averaging 7 to 8 millimeters of overlap). That’s a strong result, though most patients still needed refinement trays to close the remaining gap between where their teeth ended up and where they needed to be.
Mild crowding, where teeth overlap just a few millimeters, tends to resolve quickly and predictably. Moderate crowding responds well too, though your orthodontist may use small tooth-colored attachments bonded to certain teeth to give the aligners more grip. In some cases, a tiny amount of enamel is shaved between teeth (a painless process called interproximal reduction) to create the space teeth need to shift into position.
Gaps Between Teeth
Invisalign can close most gaps up to about 10 millimeters wide. Small to moderate gaps, the kind you might have between your front teeth or scattered throughout your smile, respond well to aligners alone. Larger gaps (6 millimeters and above) sometimes require additional tools like light elastics or precision springs to guide the roots into their final positions, not just the visible crowns.
Gaps that result from missing teeth are a different situation. Aligners can sometimes close the space left by a missing tooth, but more often orthodontists will use Invisalign to redistribute spacing evenly so a dental implant or bridge fits properly later.
Overbites and Underbites
An overbite, where your upper front teeth overlap too far over the lower ones, is treatable with Invisalign in mild to moderate cases. The aligners use a feature called precision wings, small built-in extensions that encourage your lower jaw to shift forward into better alignment with the upper jaw. Combined with attachments that help grip and reposition individual teeth, this approach can meaningfully reduce an overbite over the course of treatment.
Underbites, where the lower teeth sit in front of the upper teeth, are trickier. Invisalign can correct underbites caused by tooth position, meaning the jaw itself is fine but the teeth have drifted into a poor relationship. If the underbite stems from the lower jaw being physically larger or more forward than the upper jaw (a skeletal issue), aligners alone typically can’t fix it. Those cases often require jaw surgery or a combination of braces and surgical correction.
Crossbites
A crossbite happens when some upper teeth sit inside the lower teeth instead of outside them. Invisalign can correct dental crossbites, where the issue is tooth tilt rather than jaw structure, by gradually pushing the affected teeth outward or inward into their proper positions. Attachments are almost always used in crossbite cases to give the aligner enough leverage.
For children still developing their jaws, a product called Invisalign First can achieve up to 8 millimeters of dental arch expansion, which helps correct crossbites early and creates room for permanent teeth to come in properly. This early treatment (called Phase 1) often simplifies or shortens a second round of orthodontics during the teen years.
Open Bites
An open bite means your front teeth don’t touch when you bite down, leaving a visible gap even with your back teeth fully together. Invisalign can treat anterior open bites, but the results tend to fall short of what the software predicts. A study in the American Journal of Orthodontics found that patients achieved about 66% of the planned bite closure. That’s meaningful improvement, but it means your orthodontist will likely need to build in extra movement to compensate for the shortfall.
Interestingly, the study found that changing trays every two weeks (rather than weekly) actually produced about half a millimeter more bite closure on average. The specific method used to close the bite, whether by pushing front teeth down, pushing back teeth up, or a combination, didn’t significantly change the outcome.
What Invisalign Struggles With
Not every tooth movement is equally predictable with clear aligners. Rotation is one of the hardest movements to achieve, especially for canines (the pointed teeth next to your front teeth). Research from UT Health San Antonio found that canine rotations greater than 15 degrees were significantly less accurate than smaller rotations. The accuracy rate for rotating upper canines was just 32%, compared to about 54% for front incisors. If your canines need substantial rotation, your orthodontist may recommend traditional braces for that phase of treatment.
Vertical tooth movements are another weak spot. Pushing teeth up into the gumline (intrusion) is notoriously unreliable with aligners. Some studies have found 0% accuracy for intrusion because the teeth actually moved in the wrong direction. Pulling teeth downward (extrusion), on the other hand, tends to be highly accurate, sometimes exceeding the planned movement.
Cases That Need a Different Approach
Certain conditions fall outside what Invisalign can reliably handle. Severe crowding or spacing that requires tooth extractions is generally not a good fit for clear aligner therapy alone. The large-scale tooth movements needed after pulling teeth, especially moving roots through bone over long distances, demand more force and control than plastic trays can deliver.
Complex skeletal discrepancies, where the problem is jaw size or position rather than tooth alignment, also go beyond Invisalign’s scope. If your bite issues originate in the jaw joints, realigning teeth won’t solve the underlying problem. Active gum disease or uncontrolled tooth decay also need to be resolved before starting any orthodontic treatment, since moving teeth through unhealthy bone and tissue can make those conditions worse.
For children with developmental concerns, clear aligners may not provide the stability and control needed for proper jaw growth. Invisalign First works well for specific early interventions like arch expansion, but traditional appliances remain the standard for more complex pediatric orthodontic needs.
How Long Treatment Takes
Most Invisalign cases take 9 to 18 months from start to finish. Simple cases like minor crowding or a small gap between front teeth can wrap up in about 6 months. Complex cases involving bite correction, significant crowding, or multiple issues at once may stretch to 24 months. You’ll switch to a new set of trays every one to two weeks, with check-in appointments roughly every 6 to 8 weeks.
One thing many people don’t realize is that the first round of trays often doesn’t finish the job. Refinement trays, essentially a second (or third) set of aligners based on updated scans, are common. The crowding study mentioned earlier found that even after a full set of aligners, patients still had about 2.7 millimeters of irregularity remaining in both arches. Refinements closed most of that remaining gap, but they add weeks or months to the total timeline. When your orthodontist quotes a treatment duration, ask whether that estimate includes likely refinements.