Invisalign is a brand of clear aligners: thin, removable plastic trays that straighten teeth gradually. This article explains how the system works, what each stage of treatment involves, how long it usually takes, and what is needed to keep the result afterwards. It also covers questions that adults often ask before starting.

A short history

Orthodontics has used fixed appliances for well over a century. Stainless steel brackets and wires became standard in the mid-1900s, and bonding brackets directly to teeth followed in the 1970s, along with ceramic and lingual (behind-the-teeth) braces. Clear aligner systems, including Invisalign, appeared in the late 1990s and use digital scanning and computer planning instead of brackets and wires.

How the technology works

Treatment starts with a digital scan of the teeth, which is turned into a 3D model. Planning software is used to map how each tooth should move, step by step, from its current position to the planned one. A series of aligners is then made, each shaped slightly differently from the last.

The aligners are made from a flexible thermoplastic. Each set applies gentle, targeted pressure to particular teeth. As the sets are worn in order, usually for one to two weeks each, the teeth move in small increments. Because the trays are smooth and fit closely, they are less likely to rub the gums and cheeks than brackets and wires.

Steps in treatment

Assessment. The teeth, gums and bite are examined, and goals and concerns are discussed.
Records. Digital scans or impressions, photographs and X-rays are taken.
Treatment plan. The movements are planned in software, which can show a simulation of how the teeth are expected to move.
Aligners. The aligners are made and supplied, often several sets at a time.
Wearing the aligners. They are worn for 20–22 hours a day and changed as directed, usually every one to two weeks.
Check-ups. Progress is reviewed, often every six to eight weeks, and the plan adjusted if needed.
Retainers. After treatment, retainers keep the teeth in their new positions.

What Invisalign can treat

Clear aligners are used for crowding, gaps, and some overbites, underbites and crossbites, most often in mild to moderate cases. Severe bite problems, large tooth movements or significant jaw discrepancies may be better treated with fixed braces, specialist orthodontic care or, occasionally, surgery. A thorough assessment is needed to decide what suits a particular case.

Compared with braces

Appearance: clear aligners are much less noticeable than metal brackets.
Comfort: smooth plastic tends to cause less irritation to the cheeks and gums.
Eating: aligners come out for meals, so there are no food restrictions.
Cleaning: teeth can be brushed and flossed normally with the aligners out.
Responsibility: aligners only work while they are worn, whereas braces work all the time.

For a fuller comparison, see clear aligners vs braces.

Invisalign for teenagers and adults

Teenagers often prefer aligners because they are discreet and can be taken out for sport or special occasions. Adults often choose them for the same reasons, particularly in work and social settings. Adults may also have fillings, crowns, missing teeth or gum changes that need to be taken into account when planning treatment.

A common question from adults is whether aligners can manage more complex problems. Many cases can be treated, but not all; the assessment will show whether aligners, braces or a combination is most suitable.

How long treatment takes

Many treatments take around 12 to 18 months, although simple cases may take about six months and complex cases two years or more. Small changes are often noticed within a few weeks, but larger changes take months of consistent wear. Treatment time depends on the complexity of the case and on how consistently the aligners are worn.

Wearing aligners as directed

Aligners should be worn for 20–22 hours a day and taken out only to eat, drink anything other than water, and clean the teeth. Missed hours slow tooth movement and can mean extra aligners or a longer treatment. Some people find it helps to set phone reminders, keep the aligner case somewhere visible, or link aligner wear to meal and brushing routines.

Eating and drinking

Aligners come out for meals, so no foods need to be avoided as with braces. Only water should be drunk with the aligners in: coffee, tea and red wine can stain them, and sugary or acidic drinks trapped against the teeth raise the risk of decay. Put the aligners back in soon after eating, once the teeth have been cleaned.

Looking after teeth and aligners

Brush after meals and snacks before putting the aligners back in, and floss daily.
Clean the aligners daily with a soft toothbrush and mild soap, or a cleaner made for clear aligners. Rinse them in lukewarm water.
Avoid hot water and harsh chemicals, which can warp or cloud the plastic.
Keep the aligners in their case when they are out of the mouth.
Keep up regular dental check-ups during treatment.

Discomfort and other side effects

Mild pressure or soreness is common for a few days after starting each new set of aligners. Over-the-counter pain relief such as paracetamol or ibuprofen can help, and orthodontic wax can be used on any edge that rubs. Some people have a slight lisp at first, which usually settles within a few days. Pain that persists should be checked by a dentist.

After treatment: retainers

Teeth can drift back towards their old positions after treatment, so retainers are needed. They may be clear removable retainers or a thin wire bonded behind the front teeth. Removable retainers are often worn full-time at first and then at night only, as advised. Regular check-ups help make sure retainers still fit.

Good oral hygiene and a diet low in sugar continue to matter after treatment, to keep the newly aligned teeth healthy.

Common questions

Are the results permanent?

Results last as long as the teeth are kept in place, which means wearing retainers as advised. Without them, teeth can shift back.

Are the results the same as with braces?

For many problems the results can be comparable. The outcome depends on the type of problem and on how consistently the aligners are worn.

Is treatment covered by health funds?

Some extras policies include orthodontic cover. Check with your health fund to find out what applies to your policy.