How aligners move teeth
Each tray is made to a shape a fraction different from where your teeth sit now. Once seated, it flexes over the teeth and pushes them toward that shape. Steady light pressure remodels the bone around the root, which is how teeth move whether the force comes from a tray or from a wire.
The sequence is planned in advance and the trays are made in order. You wear each one for the prescribed interval, usually a week or two, then move to the next. The movement per tray is deliberately small, because heavier force does not move teeth faster and can damage the ligament and shorten roots.
Attachments, IPR and refinements
Aligner treatment involves more than the trays themselves. These come up in most cases, and they are easier to plan for when they are explained at the start.
- Attachments
- Small tooth-colored bumps bonded to certain teeth to give the tray something to grip. Without them a smooth tray tends to slide over a rounded tooth instead of turning it. They come off at the end of treatment.
- Interproximal reduction
- Called IPR. A fraction of a millimeter of enamel is polished from between certain teeth to make room for crowded teeth to line up. It is how crowding is often resolved without an extraction.
- Buttons and elastics
- Some bite corrections need elastics hooked between the upper and lower arches, attached to small buttons. They are visible while worn, and they are part of the plan you agree to before you start.
- Refinements
- A second set of trays made partway through, once the teeth have moved and the plan needs updating to match their current positions. Most cases include at least one round, and it is a routine part of treatment.
What aligners handle well, and what they handle less predictably
Aligners have improved a great deal, and some movements are still harder to achieve with them than others. The division is roughly as follows.
- Handled well: crowding and spacing. Mild to moderate crowding, gaps, and relapse after teenage braces. This covers much of adult treatment.
- Handled well: tipping teeth into line. Teeth that need tilting rather than moving bodily respond predictably.
- Handled well: alignment before restorative work. Small targeted movements so that a crown, bridge or implant fits properly.
- Difficult: severe crowding. When teeth have to travel a long way, or teeth have to come out to make room, fixed appliances give better control of the outcome.
- Difficult: round teeth and large rotations. Canines and premolars are close to cylindrical, so a smooth tray has little to grip when it needs to rotate one. Attachments help, though they do not resolve it entirely.
- Difficult: bite discrepancies and molar movement. Correcting a marked overbite, underbite or crossbite, or moving molars bodily through bone, is where aligners are least predictable, and those cases usually do better with an orthodontist.
An examination and records show which group a case falls into. Orthodontics covers what is referred.
Supervised treatment and mail-order aligners
Aligners ordered online without an in-person examination are a different product from aligners planned in a dental office. The comparison below shows what each one includes.
| Consideration | Planned in a dental office | Mail-order aligner kits |
|---|---|---|
| Examination and x-rays | A full examination and x-rays before anything moves, so decay, infection and bone loss are found first. | A self-taken impression or a scan taken at a kiosk. X-rays and an in-person examination are not part of the process. |
| Gums and bone | Assessed and treated first, because moving teeth through diseased gum tissue can lead to bone loss. | Gum and bone health are not assessed before treatment begins. |
| Attachments and IPR | Available, which is what makes rotations and crowding correctable. | Generally not offered, so treatment is limited to what an unmodified tray can do. |
| When it goes wrong | The dentist who planned the treatment examines the problem and adjusts the plan. | Support is handled remotely by the company, and correcting an unwanted result is a separate course of dental treatment. |
Retainers
On the day the last tray comes out, the teeth are held by fibers that have spent months being stretched, and those fibers pull. Without retention, teeth tend to relapse toward where they started. Crowding that returns after earlier orthodontic treatment is often the result of a retainer being set aside.
Plan on a removable retainer worn at night with no end date, a thin wire bonded behind the front teeth, or both. A bonded wire needs checking, because one that comes loose at one end can move a tooth on its own.
Common questions about clear aligners
Will clear aligners work for my teeth?
It depends on what has to move and how far. Some cases suit aligners, some do better with fixed braces, and some belong with an orthodontist. Records and an examination are what answer that question.
Does it hurt?
The first two or three days on each new tray feel tight, and teeth can be tender to bite on. The tenderness fades. Changing trays before bed helps, because the tightest period passes during sleep.
Can I drink coffee with them in?
Water only. Hot drinks can distort the plastic, and anything sugary or acidic sits against the enamel with nowhere to drain. That combination can cause new decay while the teeth are being straightened.
How much does it cost, and does insurance help?
The fee depends on the number of trays and the complexity, so it is calculated after records and discussed with you before treatment starts. Some dental plans include an orthodontic benefit and many do not, so review the details of yours. See insurance and payment options.