How Do Clear Aligners Work?

Whether due to genetics, habits, or a combination of forces, many of us have misaligned teeth. Fortunately, there are plenty of treatment options to correct dental misalignments, and clear aligners are among the most popular.

But one piece of the puzzle is missing: knowing exactly how these mysterious dental appliances work. In this guide, we’re bridging the knowledge gap, helping you as a patient and consumer better understand how clear aligners move your teeth. Let’s jump in!

How Teeth Move: The Basics

Our teeth are rooted in place — even if that place isn’t ideal. Moving them requires altering this “root” so they can move. Three main parts of the dental anatomy keep them in their positions: the gingiva (gums), jawbone, and periodontal ligament.

When teeth move on their own, it’s usually due to oral health issues negatively impacting one or more of these parts. For example, someone with gum disease or bone loss might notice their teeth have shifted position in recent years and their bite no longer comes together correctly. But when the teeth are intentionally moved — through the use of braces, aligners, spacers, and other orthodontic devices — it’s because force is directed against the teeth.

This force needs to be strategic. It has to be directed against specific teeth and in a specific direction, controlled down to a fraction of a millimeter. It also must be powerful enough to get the desired movement but gentle enough to ensure that movement takes place over days, even weeks, not hours. Rapid movement can lead to root resorption and tooth loss.

This force loosens the periodontal ligaments on one side of the tooth while compressing them on the other, allowing the tooth “wiggle room.” The tooth moving then influences the gums and bone to remodel around it as it travels to its ideal position. Two types of bone cells are generated in this process. Osteoclasts promote bone remodeling on the side of the compressed ligaments, and osteoblasts generate bone growth on the side with stretched ligaments.

Once the tooth reaches this spot, it is held in place using retainers, allowing the ligaments to tighten up. The gums and bone then heal around the tooth, strengthening its position. However, due to the ligaments always wanting to pull back toward their old positions, retainers must be used for life. Without them, the teeth will migrate back.

How Do Clear Aligners Work?

While the underlying principles are the same with all methods of moving the teeth, the details vary. Clear aligner therapy (CAT) directs force against the teeth through shape. Each aligner is shaped slightly differently from the one before it, altering where the force is placed and how it directs the tooth or teeth it’s designed to move. The average aligner will move your teeth 1/10 of a millimeter. Aligners are worn for 1-2 weeks, so whenever the patient switches to the next in the series, they, in essence, adjust their treatment.

There are two key differences between how aligners and braces move the teeth. First, the type of force used. Braces use pull force; aligners employ a push force. The push force is considered more gentle.

The second difference is in the “adjustments.” If you have braces, the archwire is what directs the force against the teeth, and to keep your teeth moving, it needs to be adjusted every 4–6 weeks. This means that each adjustment needs to take into account all of the movement that needs to happen over the next month to month and a half.

With aligners, the adjustments come every time you change to the next in the series, so every 1–2 weeks. This allows them to focus more on individual teeth and small movements that are often more strategic and nuanced than what braces can deliver, leading to greater comfort during treatment and faster results — mild-to-moderate cases can be resolved in as little as four months.

Aligners and Attachments

When treating complex cases, aligners alone aren’t always enough to achieve the desired movements. In these situations, attachments are used to enhance treatment and get the right results. There are four main types of attachments used with aligners:

• Engagers: These are small “bumps” made from dental composite and bonded to the teeth. Since they are raised from the natural surface of the tooth, they give the aligners extra grip, generating more force and better controlling movement.
• Buttons: Sometimes, attachments need more than the tooth or aligners to connect to. In these cases, buttons are used. These intermediary attachments are bonded to the teeth and then connect to other attachments, like elastics.
• Elastics: These are rubber bands that generate additional force to make larger and more complex movements. In most cases, they are used to alter the position of the bottom jaw to bring it into alignment with the upper jaw.
• Spacers: When the teeth are too crowded for aligners to get a good grip, spacers can be placed between them. These appliances push crowded teeth apart to make room for the aligners to work better.

Aside from engagers, all of these are often used with braces treatment as well. The downside of using them with aligners is that they increase visibility, but for most, the trade-off of faster and more precise tooth shifts is worth it.

What Can Clear Aligners Treat?

In the vast majority of cases, clear aligners can move the teeth just as well as braces, though treatment scope varies based on which aligner system you use. For example, most in-office systems match braces in every area except tooth rotation and raising and lowering the teeth. Remote aligners, on the other hand, only correct mild-to-moderate misalignments in the front 6–8 teeth.

Class I Malocclusions

This class of misalignments covers cases where the relationships between the upper and lower teeth and jaws are normal, creating a balanced bite. Some alignment issues included in this class are:

• Crowding
• Spacing
• Protruding teeth
• Twisted teeth

Traditional in-office aligner systems like Invisalign, ClearCorrect and 3M Clarity Aligners can treat the full range of class I malocclusions, save for cases of significant tooth rotation. At-home clear aligners like Byte and AlignerCo can correct most of these, assuming they are mild to moderate in nature.

Class II Malocclusions

With this type of misalignment, the upper molars sit more forward than the lower ones. This prevents the bite from coming together correctly. In extreme cases, an individual might be unable to close their mouth completely or properly chew food. This can be caused by an overdeveloped upper jaw, an underdeveloped lower one, or just due to the position of the molars, without any jaw issues.

At-home aligners are unable to move the molars, so they cannot treat this type of malocclusion even when it is strictly dental in nature. Nearly all in-office systems can correct dental class II malocclusions, and the majority can address those involving jaw position through the use of attachments or when paired with other appliances.

Class III Malocclusions

This class of misalignments covers those that originate in a growth-related dentofacial deformity impacting the relationship of the lower jaw to the upper jaw and/or cranial base. Some in-office aligners can address this class of malocclusions with the help of attachments and other appliances. However, there are many cases where this class requires jaw surgery.

Cases Clear Aligners Can’t Treat

Even when boosted by attachments or used with other appliances, clear aligners have their limitations. Below are misalignments that require the use of braces instead of aligners:

• Gaps greater than 6 millimeters
• Molars rotated more than 20 degrees
• Other teeth rotated more than 30 degrees
• Teeth tilted forward at more than a 45-degree angle
• Midline discrepancies greater than 2 millimeters

Additionally, aligners struggle to grip onto certain tooth shapes and can damage some types of restorative or cosmetic dental work. This is why a detailed evaluation is important before starting clear aligner therapy.

Clear Aligner Treatment Timeline

The exact timeline for clear aligner therapy will vary between individuals based on the severity of their case, the brand of aligners they use, and whether or not they opt for nighttime-only treatment.

The standard approach is for aligners to be worn 22 hours every day, removing them only to eat and drink staining beverages. Patients move to the next aligner in the series every 1–2 weeks, following the instructions of their doctor. If they receive nighttime-only treatment, they might wear each aligner for as many as three weeks.

Keep in mind that only wearing aligners at night tends to add 1–4 months to the overall treatment timeline. Below are typical time frames for clear aligner therapy based on case severity.

• Mild-to-Moderate Cases: 3–12 months
• Moderate-to-Severe Cases: 12–18 months
• Highly Complex Cases: 18–36 months

Clear Aligner Treatment Stages

No matter the time frame, clear aligner therapy will follow the playbook, starting with an assessment and ending with retainers. While the minutia varies based on your needs, expect to encounter the following stages if you choose clear aligners.

Assessment and Planning

Before you can start clear aligner therapy, your provider must verify that you are a good candidate for treatment. With in-office systems, this involves a visual examination of your teeth, dental X-rays, and an intraoral scan (or physical impressions in some cases). If you choose remote treatment, you’ll either get an in-person scan or take your own impressions, then send these and a few photographs to the company.

Assuming you are approved for treatment, the next step is planning. Physical impressions are digitized while the data from 3D scans is directly imported into the planning software. In most cases, the software algorithm creates an initial treatment plan that can then be fine-tuned by your provider. This generates a preview of your potential future smile, which is then sent to you to either approve or request changes. Once you are happy, you either give the go-ahead and move to the next stage or decide clear aligner therapy isn’t right for you.

Expansion

The expansion stage is where most people start active treatment. During this time, the focus is on moving the teeth not so much to their ideal positions, but to make room so they can travel more easily. This stage can rely on the aligners alone or might involve attachments and additional appliances, including engagers, spacers, and palatal expanders.

Another procedure some patients need is interproximal reduction, where small amounts of enamel are removed from the teeth to create space. Keep in mind that during this stage, you may feel like your bite is getting worse rather than better and this is completely normal — don’t panic.

Alignment

Once there is room for the teeth to safely and accurately move, it’s time to get them into alignment. Proper alignment means two things: the relationships between teeth in the same arch are healthy — no crowding, no large spaces — and the teeth in both arches come together correctly when bite force is applied. The teeth tend to move a lot during this stage, requiring the ligaments to loosen up quite a bit; if you feel like your teeth are loose and wiggly, this isn’t a bad sign.

Fine-Tuning

After the alignment stage, there are usually a few very small changes needed. This can mean slightly altering the position of one tooth or shaping a few teeth to get a balanced smile. Fine-tuning is typically part of the original plan; your dentist or orthodontist looked at your smile and understood that a few little alterations would be needed at the very end.

Refinement

The refinement stage is often needed but is not part of the original plan. This happens when all the aligners have been worn, the results have been achieved, and yet something isn’t quite right.

This might be a genuine alignment issue — the teeth still not coming together perfectly, for example — or it could be a matter of personal preference — your smile is healthy, but you want a little more space here or a little less there. When refinement is needed, more aligners are designed and ordered. This stage can continue until you and your provider are happy with your smile.

Retention

This stage is essential to keeping your new, healthier smile. During the retention phase, retainers are worn to prevent the teeth from migrating back to their original positions. Some people get fixed retainers and wear them for life.

However, most people will use removable retainers and follow a gradual step-down plan, starting with wearing them all day, every day, then moving to only wearing them at night, and then eventually to just wearing them 3–4 nights a week. The critical thing to understand is that this stage never actually ends; if you want to maintain your smile, you’ll need to use retainers for life.

Best Clear Aligner Systems

It wasn’t that long ago that you had one option for clear aligners: Invisalign. Now, there are many brands to choose from. They all work using the same basic principles, though each will offer its own scope of treatment. You can divide your options into two broad categories: in-office and at-home clear aligners.

In-Office Clear Aligners

These are the aligners we tend to think of first when talking about clear aligner therapy. They’re offered by dentists or orthodontists and require an initial visit, multiple check-ups throughout treatment, and a final visit to wrap things up. These systems are defined by the following qualities:

• Direct, in-person doctor involvement is central to treatment
• You cannot purchase these aligners directly from the company
• Nearly all of them can use attachments and treat them as a standard element of care
• It is easy to use other appliances with them, such as palatal expanders
• They tend to have a fairly high cost, though some systems are more affordable
• Most can address 95% of cases braces can

Below are some of the most notable brands of in-office clear aligners.

Invisalign

The originator and consistent innovator of the clear aligner industry, Invisalign is the most well-known and widely available clear aligner system. When you choose them, you benefit from decades of research and experience. The drawback is that they are one of the most expensive systems on the market and are very slightly more limited than some of their competitors.

3M Clarity

When you hear the name 3M, you think of household products. However, they are also one of the most prolific dental manufacturers globally. More than just an Invisalign knock-off, 3M Clarity aligners are able to treat a wider range of conditions than any other clear aligner currently on the market, addressing rotations of up to 30 degrees rather than the standard 20. But, like Invisalign, they are one of the most expensive clear aligners on the market.

ClearCorrect

If your goal is to get treatment that treats the same cases as Invisalign but for a potentially lower price, ClearCorrect could be a good choice. They offer multiple plans so you can find the one that best fits your budget. They also use a special tri-layer plastic that many patients say is more comfortable than other aligners.

At-Home Clear Aligners

Remote treatment is a newer approach to clear aligner therapy, getting its start when SmileDirectClub launched in 2014. They are sold online and typically require you to take your own impressions of your teeth, though some companies also have storefronts that offer digital scans. These systems are defined by the following qualities:

• They are sold direct to consumers, without a doctor as a middleman
• You typically need to take physical impressions to get them
• They are priced lower than the majority of in-office treatments
• Scope of treatment is limited to mild-to-moderate class II malocclusions in the front six teeth
• Attachments and other appliances cannot be used
• The only treatment combined with remote aligners is whitening

Below are some of the most notable brands of at-home clear aligners.

Byte

Our top choice for home teeth straightening, Byte advertises an average treatment plan length of 4–5 months with their all-day system. They also back your smile with a lifetime guarantee, valid as long as you follow your treatment and retention plan. Finally, they have a nighttime-only option for those who want to simplify their treatment.

Candid

In truth, Candid is not a fully remote system; they would more accurately be classed as a hybrid treatment. You start with an in-person visit or two, handle check-ins remotely (except if something goes wrong), then finish up with one more office visit. The only real drawbacks are the cost (the starting price is over $1,000 higher than most remote options) and finding a dentist.

SmileDirectClub

The way Invisalign is the originator of in-office clear aligners, SmileDirectClub is the company that launched the remote revolution. They’ve straightened over a million smiles since their launch, making them the most prolific provider on the market. They also have SmileShops where you can get in-person scans. Their biggest downside is spotty customer service.

Final Thoughts

Clear aligners work similarly to braces in that they place force against the teeth to move them, and athough they work slightly differently, they’ve  straightened millions of smiles over the years.

The key to getting good results is working with the right doctor or company and selecting an aligner system that is suited to your specific type and severity of misalignment.