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Not everyone has crooked teeth top and bottom. For plenty of people, the upper teeth already look great and it's just the lower front teeth that have drifted — or the other way around. So a very reasonable question comes up: if only one arch needs work, do you really have to pay for and wear aligners on both?
The short answer is that single-arch treatment is real, common, and often the right call — but only when the numbers line up. Whether you can straighten just your top or bottom teeth depends less on how they look and more on how they meet when you bite down. This guide breaks down when one arch is enough, when both are non-negotiable, and how Smile Perfect's dentist-led process tells the two apart before you ever pay.
Your teeth sit in two arches: the upper arch (maxillary) and the lower arch (mandibular). Most clear aligner treatment is dual-arch — you wear a tray on the top and a matching tray on the bottom, and both sets of teeth move together.
Single-arch treatment means you only wear aligners on one arch — top or bottom — because only that arch needs correcting. The other arch is left alone because it's already well-positioned and moving it wouldn't improve anything. It's the same technology and the same gentle, sustained pressure that shifts teeth — just applied to half the mouth.
Yes — in many cases you can. But there's an important catch that surprises people: your teeth don't move in isolation. The top and bottom arches are designed to fit together like puzzle pieces. When you shift one arch, you change how those pieces meet.
That's why "only my bottom teeth are crooked, so I'll just fix those" isn't automatically true. If straightening the bottom arch throws off how your upper and lower teeth come together — your bite, or occlusion — then single-arch treatment can create a new problem while solving an old one. The deciding question is never just "which teeth look crooked?" It's "can I move this arch without harming the bite?"
The one-sentence ruleSingle-arch treatment works when the crookedness is isolated to one arch and your bite already fits together correctly. When both of those are true, there's no reason to move teeth that are already doing their job.
These are the situations where treating a single arch tends to make sense. If one or more of these describes you, there's a good chance you're a candidate — though only a clinical review can confirm it.
Your lower front teeth overlap slightly, or your upper teeth have a small gap you'd like to close — while the opposite arch is already straight and even.
Very common. People who wore braces as teenagers often see their lower front teeth crowd again years later because they stopped wearing a retainer. The top usually holds — so only the bottom needs a small correction.
One tooth that's turned or leaning, with everything around it in good shape. Isolated, small movements are exactly what single-arch plans handle well.
If your upper and lower teeth already meet the way they should — no significant overbite, underbite, or crossbite — then moving one arch a little won't disturb a bite that's already healthy.
Just as important is knowing when single-arch treatment won't work. Trying to shortcut these situations usually leads to a worse bite, not a better smile.
Notice the pattern: single-arch treatment is about alignment within one arch, while dual-arch treatment is needed whenever the relationship between the two arches has to change. Bite corrections almost always require both.
Here's the concept that ties everything together. When you close your mouth, your upper and lower teeth interlock in a specific pattern called occlusion. A healthy bite spreads chewing forces evenly and keeps your jaw comfortable.
Now imagine moving your lower front teeth outward to uncrowd them, but leaving the top untouched. Those lower teeth now sit in a slightly different spot — which can change where they hit the uppers. In a mild case, that's fine. In a bigger case, it can create a spot where teeth clash or no longer meet, which affects chewing and comfort.
This is exactly why a 3D treatment plan reviewed by a dentist matters so much for single-arch cases. The plan simulates the ending bite, not just the ending look. If moving one arch keeps the bite healthy, single-arch treatment is approved. If it doesn't, a dual-arch plan protects your long-term result — and a good provider will tell you that upfront rather than sell you a plan that looks good for a month and causes problems later.
Why the lower arch is the usual candidateThe lower front teeth are the most common spot for adult relapse and minor crowding, and they're often the least visible when you smile. That's why "just the bottom" is the single-arch request providers hear most.
Take the free assessment and get a dentist-reviewed 3D preview of your result. You'll see exactly what needs treating before you pay a cent.
Check My Candidacy →When you're a genuine candidate, treating only one arch comes with real advantages over a full dual-arch plan:
That said, "cheaper and faster" is only a benefit if single-arch treatment is actually right for you. Choosing it when your bite really needs both arches isn't a saving — it's a compromise on your result.
You don't have to figure this out on your own — and you shouldn't. Here's how the decision actually gets made:
You start by checking whether clear aligners suit your case. A few questions and photos give the clinical team a first read on your teeth and bite.
Your impressions become a digital model. The dental team maps out the movements and models the final bite — this is the step that reveals whether one arch or both is needed.
A dentist signs off on the plan, and you get a preview of your projected result. If a single-arch plan delivers a great, stable outcome, that's what you're offered. If it doesn't, you'll be told why.
Because the preview comes first, you approve the plan — single or dual arch — before committing. It's backed by the Smile Perfect satisfaction guarantee.
| Single Arch | Dual Arch | |
|---|---|---|
| What it treats | Top or bottom teeth | Top and bottom teeth |
| Starting price | From $549 | From $599 |
| Best for | Isolated crowding, spacing or relapse on one arch | Bite issues, or crowding on both arches |
| Typical timeline | Often shorter (fewer trays) | Standard treatment length |
| Whitening + retainers | Included | Included |
| Dentist-reviewed 3D plan | Included | Included |
The $50 difference is smaller than most people expect — which is a good thing. It means the choice between one arch and two should come down to what your bite needs, not what you're trying to save. See current plans and inclusions on the pricing page, or browse the full aligner packages.
Take the free assessment, preview your results in 3D, and only pay when you're happy with the projection. Starting at just $549 — everything included.