Does Invisalign Hurt? What Studies of Clear Aligners Show

Why teeth feel sore

Orthodontic treatment moves teeth by pressing on them gently and steadily. Clear aligners do this with a series of removable plastic trays, each shaped slightly differently from the last; fixed braces do it with brackets and a wire. The tissues around the roots respond to that pressure, and for a while the teeth can feel tender, tight or sensitive when you bite.

People describe it as an ache or pressure rather than a sharp pain. It is usually most noticeable when chewing. How much it bothers you varies from person to person, and this article cannot predict it for you. What it can do is tell you what the studies found, and how sure they are.

The first week

The NHS says teeth may be sore for a few days¹ after braces are fitted, and suggests soft food and painkillers. Aligners behave in a similar way when treatment starts.

Most of the 12 studies in a review comparing aligners with fixed braces followed patients through the first week. In both groups, pain was usually highest in the first 24 to 48 hours and then gradually eased², fading over about a week.

In these studies, the first two days were usually the worst, and the tenderness settled as the week went on.

Do aligners hurt less than braces?

A little, for a few days, in some studies. Not reliably after that. And the evidence is weaker than it sounds.

• The first days. A review of seven studies, all of one aligner brand and in adults with mild problems, found less pain with aligners than with fixed braces during the first few days³. After that, up to three months, no difference was found.
• Only on some days. The review of 12 studies found lower pain with aligners only on days 3 and 4², with no difference at 4 hours, 24 hours, day 2 or days 5 to 7.
• Later months. One study in that review followed patients every month for a year. From the second month on, patients with aligners reported more pain² than those with fixed braces. It is a single study, but it shows that aligners do not always hurt less.

How certain is this? It depends on the review. The authors of the 12-study review rated the evidence on pain scores as very low. In the seven-study review, the non-randomised studies were rated low and its single randomised trial high. The seven-study review covered only one brand, in adults with mild problems, so its results may not apply to everyone.

Does each new set of aligners hurt?

People often ask whether each new set of trays brings the soreness back. The research does not tell us much about this. The reviews above measured pain mainly when treatment started, mostly over the first week; a few studies looked at later adjustments, but pain after each change of trays has not been studied systematically. Soreness may come back with a new set, but we cannot say how much or for how long.

The same goes for taking the trays out and putting them back in: we found no study that measured pain when removing aligners. If removing them hurts more than a little, ask your orthodontist to check the fit.

What helps with the soreness

Painkillers. A Cochrane review of 32 randomised trials found that over-the-counter painkillers reduced orthodontic pain compared with taking nothing or a placebo⁴, at 2, 6 and 24 hours (moderate-quality evidence). Anti-inflammatory painkillers (NSAIDs) and paracetamol were not shown to differ⁴ (low-quality evidence). Follow the leaflet, and ask a pharmacist or doctor if you are unsure which suits you.

Soft food. Aligners are taken out to eat. Eating soft food for the first days, as the NHS suggests¹, makes chewing easier while the teeth are tender. It has not been tested in trials, but it is safe.

Things with little evidence. Another Cochrane review looked at non-drug methods. For chewing aids such as gum or bite wafers, and for vibration devices, the evidence was of very low quality and inconclusive⁵. For low-level laser it was of low quality, and the authors said they could not rely on the findings. Harms were not measured. These are not proven ways to reduce pain. No review we found tested aligner "chewies" for pain. With fixed braces, the NHS advises not to chew gum, because it can get stuck¹.

Keep wearing the trays as prescribed. It can be tempting to leave them out when your teeth ache, but the treatment depends on wearing them for the hours your orthodontist sets.

When to contact your orthodontist or a dentist

Soreness in the first days is expected. Contact your orthodontist if:

• teeth are still painful more than a few days¹ after starting or after an adjustment
• one tooth hurts much more than the others, or hurts on its own without pressure
• an edge of a tray cuts your gum, tongue or cheek, or a sore does not settle
• a tray no longer fits, cracks or is lost

Emergencies. Facial swelling, a fever or throbbing pain is not an expected part of orthodontic treatment: see a dentist without waiting. If you find it hard to breathe or swallow, or swelling spreads quickly in your mouth or neck, call 112 or go to the nearest emergency department.

Frequently asked questions