Invisalign works best for mild to moderate alignment issues, generally handling up to 5 mm of crowding or spacing in a single course of treatment. It can correct a range of common problems including crooked teeth, gaps, overbites, underbites, crossbites, and open bites, but it has real limits once cases become more complex. Understanding where those limits fall can help you figure out whether clear aligners are a realistic option for your teeth.
Crowding and Spacing
Crowding and spacing are the two most common reasons people look into Invisalign. When teeth overlap or sit too close together, the aligners apply gradual pressure to shift each tooth into its correct position. For gaps between teeth, the process works in reverse, pulling teeth closer together over a series of trays.
The sweet spot for Invisalign is 1 to 5 mm of crowding or spacing. Cases beyond 5 mm become significantly harder for aligners to manage, and anything past 6 mm of space per arch (your upper or lower row of teeth) falls outside what Invisalign can reliably close. If you have severe crowding that would require tooth extractions to create room, traditional braces are typically the better route, since Invisalign isn’t designed to manage the large-scale tooth movement that follows extractions.
Overbites and Deep Bites
An overbite is the vertical overlap between your upper and lower front teeth. Some overlap is normal. Dentists describe it as a percentage, and 5 to 25 percent is considered ideal. When the overlap is significantly larger than that, it’s called a deep bite, and it can cause your lower teeth to wear down or create jaw pain over time.
Invisalign can correct overbites and deep bites, though the results don’t always match the digital prediction perfectly. One clinical study found that actual overbite correction achieved with Invisalign was about 29 to 39 percent of what the software initially predicted. That doesn’t mean treatment fails, but it does mean many patients need additional rounds of aligners (called refinements) to get closer to their goal. On average, Invisalign patients go through about 2.5 refinement scans before finishing treatment, and only about 6 percent complete their plan without any refinements at all.
Underbites and Crossbites
An underbite occurs when your lower teeth sit in front of your upper teeth. A crossbite is similar but may affect just a few teeth on one or both sides. Invisalign can address mild versions of both, particularly when the issue is dental rather than skeletal. That distinction matters: if your bite problem comes from the way your teeth grew in, aligners can often help. If it comes from the size or position of your jawbones themselves, aligners alone won’t be enough, and you may need braces, surgery, or a combination.
Invisalign can shift your midline (the imaginary line between your two front teeth) by up to 2 mm to the left or right per arch. Anything beyond that requires braces.
Open Bites
An open bite means your upper and lower front teeth don’t touch when you close your mouth, leaving a visible gap. Invisalign addresses this by slightly pushing the back teeth upward (intrusion), which allows the jaw to rotate and the front teeth to come together. Even a small amount of molar intrusion, around 1 mm, can produce 2 to 3 mm of bite closure through this rotation effect.
The limit is tight, though. Aligners can predictably intrude back teeth by only about 0.5 to 1 mm. Larger open bites may require temporary anchoring devices (tiny screws placed in the bone) to supplement the aligners, or a switch to braces entirely.
Rotated Teeth
If a tooth has twisted in its socket, Invisalign can rotate it back into position, but only within certain limits. Canine teeth (the pointed ones next to your front teeth) become significantly harder to rotate accurately beyond 15 degrees. Research from UT Health San Antonio found that canine rotations greater than 15 degrees were statistically less accurate than smaller rotations. For molars, the threshold is around 20 degrees. Front teeth and premolars tend to be somewhat more forgiving, but large rotations in any tooth push the boundaries of what aligners can grip and control.
Teeth that are severely tilted forward or backward also present challenges. If a tooth is tipped more than 45 degrees, Invisalign generally can’t pull it upright effectively.
How Attachments Expand What’s Possible
On their own, smooth plastic trays can only push teeth in limited directions. That’s where attachments come in. These are small tooth-colored bumps bonded directly to certain teeth during treatment. They act like tiny handles, giving the aligner something to grip so it can apply force at specific angles. Attachments make movements like rotation, pulling teeth downward, and pushing teeth upward more predictable. Your orthodontist places them strategically based on which teeth need the most help, and they’re removed at the end of treatment.
Existing Dental Work
Crowns generally work fine with Invisalign. The aligners are custom-shaped to fit over them, though your provider will monitor crowned teeth to make sure the trays aren’t applying too much pressure. Dental implants are a different story: because an implant is fused to your jawbone, it cannot be moved by aligners or braces. Invisalign can still move the teeth around an implant, but the implant itself stays put.
Bridges create the biggest complication. Because a bridge connects multiple teeth into one fixed unit, the teeth involved can’t move independently. Invisalign can work around a bridge by moving other teeth in the arch, but it limits what the overall treatment can accomplish. Porcelain veneers can also be tricky, since attachments sometimes don’t bond well to their surface.
If you’re planning any new dental work like crowns or veneers, it needs to wait until after Invisalign treatment is finished. Changing the shape of a tooth mid-treatment means the remaining aligners won’t fit properly.
Cases That Need Braces Instead
About 1 in 6 patients who start with Invisalign end up switching to braces during treatment, according to one clinical study. The most common reasons involve movements that exceed what aligners can deliver:
- Severe crowding or spacing over 5 to 6 mm per arch
- Large skeletal discrepancies where the jaw itself needs repositioning
- Significant tooth rotation beyond 15 to 20 degrees depending on the tooth
- Major vertical movement of back teeth, where aligners have almost no ability to push molars up or pull them down
- Teeth with unusual shapes like short, round, or pegged teeth that don’t give the aligner enough surface to grip
The digital treatment plan you see at the start of Invisalign (called a ClinCheck) can look perfect on screen, but the actual results often fall short of the prediction. In one study, all the computer-predicted outcomes would have met professional orthodontic standards, yet only 47.5 percent of the actual finished results in mild cases met those same standards, and zero percent did in more complex bite correction cases. That gap between prediction and reality is why refinements are so common and why setting realistic expectations matters.
Typical Treatment Timelines
Simple cases with minor crowding or spacing often finish in six to nine months. Moderate cases involving bite correction or more movement typically take twelve to eighteen months. Complex cases can stretch to two years or longer, especially when multiple rounds of refinements are needed. Your actual timeline depends on how well your teeth respond to the trays, how consistently you wear them (the standard recommendation is 20 to 22 hours per day), and whether your case involves movements that push the limits of what aligners can do.