An aligner is a custom-made, removable plastic tray that fits snugly over your teeth and gradually shifts them into straighter positions. Unlike traditional metal braces, aligners are nearly invisible and can be taken out for eating and brushing. You wear a series of these trays, each one slightly different from the last, and over the course of several months your teeth move into alignment. Treatment typically lasts 6 to 18 months depending on complexity.
How Aligners Move Your Teeth
Each aligner tray is shaped just slightly differently from your current tooth positions. When you put one in, it doesn’t quite fit perfectly on purpose. That tiny mismatch creates gentle pressure against specific teeth, nudging them in the direction they need to go. The tray deflects and stretches over your teeth when inserted, and once it’s seated, the built-in force features apply steady pressure throughout the day.
What happens inside your jaw is more interesting. When the aligner pushes on a tooth, it compresses the ligament connecting the tooth to the bone on one side. Blood flow drops in that compressed area, triggering your body to break down a small amount of bone there. On the opposite side, where the ligament is being stretched, your body builds new bone. This cycle of breaking down and rebuilding is how the tooth physically relocates within your jawbone. It’s the same biological process that traditional braces use, just delivered through plastic instead of metal wires.
You typically switch to a new tray every one to two weeks. Each new tray picks up where the last one left off, moving your teeth another fraction of a millimeter. The movements are small and incremental, which is part of why the process feels relatively gentle compared to the tightening appointments associated with metal braces.
What Aligners Are Made Of
Most aligners are made from medical-grade thermoplastics, meaning plastics that become moldable when heated and harden when cooled. The three most common materials are polyethylene terephthalate glycol (PETG), thermoplastic polyurethane (TPU), and ethylene vinyl acetate (EVA). Each has different properties. PETG is rigid and transparent. TPU is more flexible. EVA is softer and more elastic.
Some brands use a single-layer design, while others layer different plastics together. Invisalign, for example, uses a multilayer structure with softer outer layers and a stiffer core. This layered approach affects how the aligner delivers force and how it wears over time, though the multilayer design can also make it more prone to staining.
Safety concerns about BPA (a chemical found in some plastics) come up frequently. Some aligner materials do contain trace amounts of BPA compounds, but in commercially available products, these are fully reacted during manufacturing, meaning they don’t leach into your body. PETG in particular has shown no detectable hormonal effects in lab testing, making it one of the cleanest options available.
What Aligners Can and Can’t Fix
Aligners work well for mild to moderate orthodontic problems: crowded teeth, gaps between teeth, teeth that are slightly rotated or tipped, and minor bite issues. For these cases, research shows that the results are comparable to what traditional braces achieve. The difference in outcomes between aligners and braces for mild to moderate cases, while measurable in studies, is generally not noticeable to patients.
Where aligners hit their limits is with severe misalignment. Complex bite corrections, significantly rotated teeth, and major jaw discrepancies still respond better to conventional braces, which can apply more precise, stronger forces in multiple directions. If your orthodontist evaluates your teeth and finds a severe malocclusion, they’ll likely recommend braces or a combination approach rather than aligners alone.
Daily Wear and Treatment Length
Aligners need to stay in your mouth 20 to 22 hours a day to work properly. You remove them only for eating, drinking anything other than water, and brushing your teeth. That leaves roughly two to four hours of total removal time per day, which sounds tight but becomes routine quickly. Falling significantly below that wear time slows your progress and can throw off the entire treatment plan.
Most people finish treatment in 6 to 18 months. Minor spacing issues on the shorter end, bite corrections and larger gaps on the longer end. Your orthodontist maps out the full sequence of trays at the start using digital planning software, so you’ll have a clear estimate of your timeline before you begin.
How Aligners Are Designed and Built
The process starts with a 3D scan of your mouth. An intraoral scanner captures a precise digital model of your teeth, gums, and bite. This scan is more accurate for aligner fabrication than traditional putty impressions. From there, orthodontic software maps out every stage of tooth movement from your current positions to the final result, generating a unique tray design for each step.
The digital model is then sliced into printable layers and sent to a 3D printer. After printing, each tray goes through post-processing (trimming, polishing, and quality checks) before being shipped. Some orthodontic offices now have the equipment to handle this entire workflow in-house, from scanning to printing, which can speed up the process and allow for quicker adjustments if something needs to change mid-treatment.
Keeping Aligners Clean
Because aligners sit directly against your teeth for most of the day, bacteria build up on them quickly. The surface of an aligner, even a brand-new one, has microscopic ridges and scratches where bacteria latch on and form biofilms. After about two weeks of wear, trays develop microcracks and abraded areas that make bacterial growth even easier. Unlike your natural teeth, aligners don’t benefit from the self-cleaning friction of your lips and tongue, so bacteria accumulate faster than you might expect.
Poor aligner hygiene has real consequences. The bacterial buildup can disrupt the natural balance of microbes in your mouth, increasing your risk of cavities, gum disease, and persistent bad breath. Stained, cloudy trays also defeat the cosmetic purpose of choosing clear aligners in the first place.
The most effective cleaning approach combines mechanical and chemical methods. Brushing your aligners with a soft toothbrush removes the bulk of the biofilm. Following that with a chemical soak, either a cleaning tablet designed for aligners or an antibacterial mouthwash, significantly improves the results compared to brushing alone. If you want to go further, ultrasonic cleaning devices paired with an appropriate detergent have been shown to be the most effective protocol of all. At minimum, rinse your aligners every time you remove them and give them a thorough clean at least once a day.
Cost Differences
In 2025, clear aligners in the United States range from about $1,000 to $8,000. The biggest factor in that spread is whether you go through an orthodontist’s office or use a direct-to-consumer service. At-home aligner companies typically charge $1,500 to $2,500, while in-office treatment costs more but includes professional monitoring, in-person adjustments, and the ability to handle complications as they arise. Many dental insurance plans now cover a portion of aligner treatment the same way they cover braces, so it’s worth checking your benefits before comparing sticker prices.