My Teeth Are Killing Me After Whitening

Written & Reviewed by Dr David Chen

Teeth sensitivity is one of the most common side effects of whitening. According to the American Dental Association (ADA), the sensitivity is usually mild and transient but it seems to be more prevalent with higher concentration whitening agents.

It seems to affect about two out of three people who undergoing whitening treatment. However the strength of the bleaching product as well as treatment length also have an influence of sensitivity occurring.

zoom whitening light

Nonetheless, everyone’s experience may be different. Perhaps you’re more sensitive towards whitening and that is why you may feel like your teeth are killing you afterwards.

Without further ado, let’s dive right into the mechanisms of why teeth whitening hurts and how it causes sensitivity. Then we’ll discuss some options for what you can do about it.

Why your teeth are killing you after whitening

There are multiple reasons as to why teeth whitening causes sensitivity but they all have to do with how the whitening agent (hydrogen peroxide) interacts with the tooth. The ultimate result is mild tooth nerve pain and sensitivity. Essentially you have pulpitis, pulp inflammation.

  • The peroxide diffuses through the entire tooth all the way to the pulp.
  • The bleaching gel’s hypertonicity and higher osmolarity pulls fluids out of the dentinal tubules.
  • The tooth whitens via a chemical reaction that oxidizes the organic matrices which contain the intrinsic tooth stains.

A short summary for how hydrogen peroxide whitens your teeth is by diffusing through it while oxidizing all of the intrinsic stains.

The whitening gel can reach the tooth nerve

Contrary to what you may have thought, the whitening agent doesn’t just bleach the enamel. The peroxide actually diffuses through the entire tooth including the pulp. According to the Journal of Endodontics, it only takes about 15 minutes from the start of the treatment for you to find traces of it at the pulp.

Smear plugs and dentinal tubules

The whitening gel can diffuse through the tooth because the peroxide dislodges and dissolves the smear plugs which are suppose to protect the dentinal tubules. Under normal circumstances the smear plugs prevent all external stimuli from traveling through the tooth. However the peroxide is potent enough to get rid of the plugs, thus providing a straight path towards the pulp.

Peroxide gel on smear plugs

Having a substance such as hydrogen peroxide which is highly acidic near the sensitive tooth nerve can be a direct cause for sensitivity. It would be unusual for it to not hurt. Think about it for a moment, if it can dissolve the smear plugs what do you think it’ll do to the pulp?

According to a study by the Journal of Dentistry, whitening is relatively safe at lower concentrations where the pulp will recover on its own. However for a higher concentration product, it can be cytotoxic to the nerve.

Hypertonicity of the bleaching gel pulls fluids out of the dentinal tubules

The hydrodynamic theory for dentin hypersensitivity states that a difference in hypertonicity or osmolarity can cause fluid shifts in the dentinal tubules. The movement of these fluids through the tubule is what elicits a sensitivity or pain response.

The whitening gel is at a much higher osmolarity than the fluids inside of the dentinal tubules. This causes all of the fluids from within to be pulled out of the tooth. The sensitivity is felt when the change in fluid pressure occurs.

Whitening chemically oxidizes intrinsic stains

The reason your teeth are yellow is because of intrinsic stains that are deeply embedded within the organic matrices of your tooth. The way the whitening agent whitens the tooth is by chemically oxidizing the organic matrices and consequently the stains within it.

opalesence boost in-office

A chemical reaction is literally taking place inside of your tooth, how can that not be sensitive? However what you should be aware of is that the sensitivity is often correlated with the concentration of the bleaching product. Whitening strips may make your teeth more sensitive but it won’t make them as sensitive as an in-office session!

How to reduce the teeth sensitivity after whitening

If your teeth are killing you from the whitening, you should try to reduce the sensitivity so that you can get some pain relief. There are a couple of things that you can do which should help.

  • OTC pain medication
  • Fluoride varnish
  • Use a desensitizer
  • Wear the whitening trays
  • Avoid irritating foods

Related content: We do have an entire guide on how to stop sensitive teeth pain.

Taking pain medication

Pain killers such as ibuprofen and acetaminophen work for more than just body aches. They can also reduce toothaches and dull the pain. If you were doing an in-office whitening session, prior to putting on the gel your dentist will usually give you some pain medication.

You can surely continue taking the pain medication for the next few days while sensitivity is persistent. Research shows that most of the post-whitening sensitivity should resolve by around the 4th day.

Fluoride varnish treatment

Studies have shown that applying a fluoride varnish treatment with 5% sodium fluoride can reduce sensitivity after teeth whitening. The sodium fluoride works by forming a layer of calcium fluoride (CaF2) which occludes all of the dentinal tubules.

In addition to that it will also form a layer of fluorapatite when it interacts with the phosphates in your saliva. The extra barrier will help shield your teeth from cold air and that will make the post-op more comfortable. Essentially, fluoride does have a desensitizing effect in high concentrations.

Use a desensitizer

Teeth sensitivity isn’t exclusive to whitening because everyday people have it. The most common cause is from gum recession where the exposed root surface extra sensitive. A popular solution would be to use a nerve desensitizing toothpaste that contain potassium nitrate.

Sensodyne Original Flavor

Fortunately for you, you can use this same desensitizing toothpaste for your post-whitening sensitivity. One of the most popular brands would be sensodyne, which they specifically market towards individuals with teeth sensitivity.

Just so that we’re clear how potassium nitrate works is that over the course of brushing for about 2 weeks, a sufficient concentration of it will build up around the pulp. Once it reaches a certain concentration it will prevent the tooth nerve from firing pain signals. If you think the sensitive toothpaste isn’t working its probably because you haven’t used it long enough.

Of course, the potassium nitrate is not permanent because it slowly gets worn away. For this reason, you have to keep on using it every single day if you wish to keep the desensitizing effect going.

Alternative desensitizer

Aside from potassium nitrate, you can also try the KoR Whitening Desensitizer. It is a unique calcium oxalate desensitizer which does not act on the pulp but rather it reclogs the opened dentinal tubules from bleaching. It basically fuses with the tubules and prevents further stimuli.

KoR Desensitizer effect on Tubules

Remember that peroxide will dislodge and dissolve the smear plugs, which creates a path straight to the pulp. What this desensitizer does is, it will recreate a plug that will block off the dentinal tubules so that additional whitening gel cannot penetrate through to the nerve.

This product works extremely well but unfortunately it is available by prescription only. That means you can’t purchase it OTC but if your dentist uses this whitening system, they’ll usually have one for you prior to starting treatment.

Allegedly, according to KoR, potassium nitrate may not be effective for certain people. This is the rough breakdown for its effectiveness:

  • 1/3 of patients will have a very good anti sensitivity result.
  • 1/3 will feel a mild improvement
  • 1/3 will not have any effect at all

Basically what they’re saying is that their product is superior. We say you should give everything a try and use whatever works for you.

Wear the whitening trays

If your product came with wearable whitening trays, it actually helps to simply wear them. What that does is, it actually creates a barrier to protect your teeth from cold air touching it. Most patients report that the sensitivity actually decreased while they’re wearing it.

Isn’t that amazing? The same trays that you used to bleach your teeth can be repurposed for combating sensitivity.

Here is another tip that most people don’t know about! You can actually put some sensodyne toothpaste into the tray and then wear it for about 30-45 minutes. That should drastically decrease the pain that you may be feeling.

The truth of the matter is that the desensitizer works based upon contact time and sometimes brushing for just two minutes isn’t sufficient. Wearing the trays with the toothpaste for an extended period of time will maximize the effect of the desensitizer.

Avoid irritating foods

If your teeth are sensitive while eating certain foods, you may want to avoid them until the sensitivity goes away. It makes no sense to cause yourself pain. The good news is that this condition should resolve within a few days. You can go back to enjoying what you like to eat after that.

Examples of irritating foods:

  • Spicy
  • Sour
  • Acidic
  • Sweet

Tip on how to minimize it prior to starting treatment

People who don’t normally have teeth sensitivity probably don’t use a sensitivity toothpaste. What tends to happen is that they don’t start using one until after they finish whitening and their teeth is already hurting.

That is actually too late for you to start the desensitizing toothpaste. The reason is that it can take up to two weeks for the potassium nitrate to build up to a sufficient concentration around your tooth nerve to block the signals.

What that means is if you’re already in pain and you start using this, you won’t actually get that much of a benefit out of it.

Instead of waiting to be in pain, what you should’ve done or what you should do next time is to actually start using sensodyne prior to starting treatment. In fact, you should start using it about 2-3 weeks before you even start the whitening. That way it gives you sufficient time to have already desensitized the nerve.

Predisposition to teeth sensitivity

There are a lot of individuals with pre-existing sensitivity issues. For those with this condition, they should expect their whitening treatment to exacerbate the sensitivity. The whitening will only make it worse.

Due to this reason, severe sensitivity may be a disqualifying criteria for teeth whitening especially if it is bad enough on a daily basis. Although that doesn’t mean you can’t try, you can still give it a go. You can always stop the treatment if it gets too bad.

Reasons for teeth sensitivity in general:

  • Receding gums. If you brush too hard or had gum disease, you may have gum recession. Once the gums recede it will expose the more sensitive root surface.
  • Eroded enamel. If you eat a lot of acidic foods, you may have enamel erosion. If your layer of enamel is thinner than normal, you’ll be more prone to the sensitivity effects of whitening.

What if you still really want to whiten, are there alternatives?

What we’ve noticed is that there is a correlation between the concentration of whitening gel and the amount of sensitivity that is felt. If your teeth can’t handle the professional in-office treatments, you may want to just stick with the OTC products.

According to studies, all concentrations of hydrogen peroxide have the potential to whiten your teeth to the same level. It is just that the more potent products will get you there faster. The less potent ones simply require a much longer treatment time to achieve the same results.

Crest 3D White strips

What that means is that you can try the whitening strips but use it for a longer period of time. It should be more gentle and cause less discomfort.

Over time if you get use to the strips and want to try something stronger, you can give the products with a tray and LED light a try such as SNOW whitening.

Original SNOW teeth whitening kit


It is not unusual for your teeth to feel like they’re killing you after finishing whitening treatment. Approximately two out of every three people will experience some sort of tooth sensitivity afterwards. It is a very common adverse effect of undergoing bleaching.

Just because your teeth hurt it doesn’t mean that you’re doing something wrong. Its just a natural part of how the peroxide works in whitening your teeth.

Fortunately for you, there are ways that you can minimize the post-operative sensitivity. You can try taking pain killers, using a desensitizer, wearing the trays, and also avoiding irritating foods. Give those tips a try and see if it helps!


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