How To Whiten Teeth Overnight – Guide

Written & Reviewed by Dr David Chen

Teeth whitening used to be available only at the dentist but as technology advanced, more options became available. There are now more do it yourself options with over the counter products than professional ones!

cartoon moon at night

Although what we’re going to talk about today is overnight whitening. Yes, forget having to sit in a dental chair for an hour, you can now whiten your teeth while you’re asleep. For these products, you simply put them on before going to sleep and once you wake up, you’ll have whiter teeth with less stains on them.

What is there not to like about that? It requires no additional time out of your busy day.

However not all whitening products can be used overnight because the vast majority of them are meant to be used while you’re awake. You also can’t use the daytime products while you sleep because there are safety concerns when you do so.

Therefore it is important that you choose the right product if you want to do it while you’re asleep. This guide will give you an overview about the options that you have if you want to wake up with beautifully white teeth.

OTC products that can whiten teeth overnight

Currently the only OTC products that can whiten your teeth overnight are the whitening pens. It is also super easy to use and will take only a minute to do it.

How to use whitening pens overnight:

  1. Brush and floss your teeth so that you have clean surface to bleach.
  2. Apply whitening gel to all of your teeth using the pen.
  3. Go to bed.
  4. Wake up with whiter teeth.
  5. Simply brush your teeth to remove the residual film over them.

However you should be aware that NOT ALL of the pens can be used overnight. Some of them permit you to do so while others do not. You must read the label carefully!

Bleaching pens that can be used while you sleep:

Crest emulsions overnight freshness

Bleaching pens that are meant for daytime:

  • Arc whitening pen
  • Auraglow pen
  • Smile direct club pen
  • SNOW extra strength serum

Why pens can be used overnight

The whitening pens are formulated in such a way that it has a low concentration of hydrogen peroxide and it forms a film over your teeth. The combination of these two factors permits it to be used while you sleep.

The main whitening agent in most products is hydrogen peroxide and that is simply how they work. The peroxide forms free radicals that can diffuse through the tooth and oxidize all of the stains.

What is important to understand is that high concentrations of peroxide can only be used for a short duration of time. While the opposite is also true in that lower concentrations can be used for a longer duration of time. In other words, overnight products require a lower concentration in order to be used safely.

Also the way the pens form a residual film over the teeth helps the peroxide stay on the teeth. It keeps the whitening gel on the teeth and prevents it from being washed away with saliva. After all, if you are able to swallow all of the bleaching gel within the first few minutes, it won’t have much time to bleach your teeth!

Professional overnight whitening products

Aside from the in-office treatments, there are also professional take home whitening kits. These are different from the OTC ones because they’re more concentrated and also use customized whitening trays.

KoR night 16% carbamide peroxide

Examples of professional take home overnight kits:

  • KoR Night 16% carbamide peroxide
  • Opalescence 10% carbamide peroxide with potassium nitrate and fluoride

What you may also find interesting is that the professional night time products all use carbamide peroxide (CP). This is in contrast to the whitening pens which use hydrogen peroxide. In case if you were wondering what the difference was between carbamide peroxide vs hydrogen peroxide, the former is a precursor for the latter. In other words, carbamide peroxide converts into hydrogen peroxide when it breaks down.

An advantage that CP has is that it is more shelf stable and doesn’t degrade as quickly. In addition to lasting longer, it also works more slowly in the mouth. You can basically think of carbamide peroxide as an extended release formula of hydrogen peroxide. Can’t really think of a better way to describe it than that!

Essentially due to its shelf stability and extended release, CP is well suited for whitening your teeth while you sleep!

How to use customized whitening trays overnight

The first thing that needs to be done is to have impressions or molds of your teeth done. Then your dentist has to make the trays and you come to pick them up after they’re done. Now you’re ready to start.

  1. Brush and floss your teeth so there is no food in the way!
  2. Apply a bead of whitening gel along the outer lip/cheek facing side.
  3. Insert trays into your mouth.
  4. Lightly press the trays to adapt them to your teeth.
  5. Using a toothbrush or q-tip, wipe away excess from the gum margins so that it doesn’t turn your gums white.
  6. Go to sleep.
  7. Wake up and brush your teeth to remove all excess.
  8. Clean your trays with a wet toothbrush only.
  9. Store trays in open container to let it air dry so that it can be used again next time.

Here is a video by Opalescence on how to use it. Other brands may be slightly different but the overall process remains relatively similar.

These overnight treatments usually require you to whiten for 1-2 weeks. However it only takes about 1-2 minutes to do it so its not an inconvenience at all. Most of the work is being completed while you’re snoring away for the next 6-8 hours.

Daytime whitening can be dangerous if used while asleep

Whitening products that are meant to be used during the daytime cannot and should not be used while you’re sleeping. The main concern is in regards to safety because the concentration is inappropriate and the delivery method of the bleaching gel is improper.

If you choose to ignore the directions on the label, you can potentially cause yourself harm and a lot of pain. Hopefully it’s not severe enough that you end up in urgent care.

Inappropriate concentration

More concentrated peroxide can whiten your teeth faster but they’ll also cause more sensitivity. Their treatment sessions are also not meant to be very long.

Less concentrated peroxide on the other hand will whiten your teeth slower but they’ll cause less sensitivity. They are meant to be used for a longer period of time and that makes them more suited for overnight treatment. Most people sleep for about 6-8 hours so you do want a product that takes that long to work.

Studies have shown that when you try to use very potent whitening gels for a long period of time, it can result in pulp toxicity. However if you decrease the whitening time or decrease the concentration, hydrogen peroxide becomes safe to use.

Basically the manufacturers of the products have already tested the concentration and what duration their product should be used for. You should follow their directions if you want to whiten your teeth safely. By trying to use it for a longer period of time it may cause harm.

Evidence of peroxide concentration and suggested treatment duration can be seen by the Opalescence products:

  • Opalescence PF 10%: 8–10 hours or overnight
  • Opalescence PF 15%: 4–6 hours
  • Opalescence PF 20%: 2–4 hours
  • Opalescence PF 35%: 30-60 minutes
  • Opalescence PF 45%: 15-30 minutes

As you can see, the recommended whitening time decreases exponentially as the concentration increases. Needless to say, if you tried using the 45% product overnight, you may end up in excruciating pain. There’s a good chance you might even need a root canal on every tooth!

Improper delivery method for bleaching gel

The overnight treatments are designed to be safely done while you’re asleep.

  • The pen creates a film that sticks to your teeth so that the gel doesn’t get washed off.
  • The customized trays hug your teeth closely so that it can work undisturbed.

You can compare that to other OTC daytime products such as the whitening strip or the trays with the LED blue light.

  • The strips have an adhesive to it that sticks to your teeth for about an hour. You don’t want to accidentally swallow the whitening strip in the middle of the night when the adhesive dissolves.
  • The products that use a LED light require you to hold a blue light in your mouth. That is fine while you’re away but certainly won’t work very well if you’re sleeping. It’ll probably fall out of your mouth after a few minutes.

Basically the ones that weren’t designed to be used while you’re asleep, its not conducive to it.


Whitening your teeth overnight is an option because you can do it with whitening pens or professional customized trays. The concentration of the product is low enough that it can safely bleach your teeth over the course of 6-8 hours. The way the gel are applied to your teeth are also more conducive to using while asleep.

The daytime products cannot be used while you’re sleeping due to inappropriate concentration and improper application methods. It may result in a lot of pain or self harm if you use it for longer than you’re supposed to.


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