Why My Teeth Are Killing Me After Whitening?

Updated: Apr 19

Did you just finish your teeth whitening procedure, they look white as snow but you're having some severe teeth sensitivity. The pain level is just shy of sending you off to the afterlife.

KoR Teeth Whitening
KoR Teeth Whitening

Table of Contents

Why are your teeth killing you after whitening?

Teeth are normally not sensitive because we have smear plugs that are blocking any type of stimuli from entering through the dentinal tubules on the tooth, which lead directly to the pulp. Photo credits goes to Dr. Rod Kurthy from KoR Whitening.

Smear Plugs
Smear Plugs

Something different happens when the peroxide based whitening gels come into contact with the smear plugs. The most notable side effect is teeth sensitivity and it occurs via these mechanisms:

  • It dislodges and dissolves the smear plugs that were naturally protecting the tubules.

  • With the smear plugs gone, the hypertonicity and higher osmolarity of the bleaching gel will pull the dentinal tubular fluid out of the tooth, causing you discomfort.

  • The gel can also directly travel straight to the nerve.

Peroxide bleaching gel on smear plugs
Peroxide bleaching gel on smear plugs

This is all based on the Hydrodynamic theory, which states that the mechanoreceptors in the pulp or nerve of the tooth can sense the movement of fluids in the dentin tubules and that causes a sharp pain signal.

  • The fluid flow mechanism was first suggested by Alfred Gysi in the 1900s.

  • Martin Brannstrom finalized it by performing experiments in the 1960s.

There are two alternative theories but this is currently the most widely accepted. It is almost inevitable to experience some discomfort and possibly some pain from undergoing this treatment just because of what naturally happens when the bleaching gel comes into contact with the smear plugs.

How to reduce sensitivity after whitening

Therefore, based on what we know from above there are two methods of decreasing the sensitivity from the procedure.

  1. Recreate a plug to block off the tubules.

  2. Desensitize the nerve so that it doesn't send as many pain signals.

The most widely available desensitizing product on the market, which accomplishes these two effects would be potassium nitrate. This ingredient is commonly found in your typical sensitivity toothpastes such as Sensodyne.

Sensodyne Toothpaste
Sensodyne Toothpaste

In order for the potassium nitrate to work, you must use the toothpaste that contains it at least twice a day for a minimum of two weeks straight. Then you need to continue using it so that it continues to block off the tubules. If you stop using it, then the plugs will disappear.

We suppose it would be correct to classify it as a temporary measure but it could be extended indefinitely as long as you keep using it.

Effectiveness of potassium nitrate:

  • 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

So, yes how effective it is will vary but please remember that you need to use it for at least two weeks because it takes awhile for the effects to start showing. It doesn't work instantaneously.

Alternative desensitizer by KoR Whitening

Just so that we are clear, our dentists in long island city solely use KoR at our office so we do endorse the product.

The KoR desensitizer will not only block off the peritubular dentinal openings but the material will also bond to the hydroxyapatite of the enamel and dentin. This creates a much stronger plug than potassium nitrate, which doesn't bond to the structure.

What this special plug is made of is actually a thin layer of calcium oxalate crystals. These crystals are very white in appearance so they do help the teeth look whiter as a side effect.

In case you were curious, that weird chalky feeling you get from eating spinach is also due to the same ingredient. Spinach contains a lot of oxalic acid and when it comes into contact with calcium in our saliva, it forms calcium oxalate! Supposedly the leafy green can help a little with sensitivity.

How to minimize the sensitivity prior to starting whitening

Now that you are aware of how potassium nitrate works in toothpastes, you know that you're suppose to start using the anti sensitivity pastes before you start the bleaching process! More precisely, at least two weeks before you even think of getting the procedure done so don't think that you can just start the treatment tomorrow. You need at least 2 weeks to prepare beforehand.

If you do not follow these instructions, we would expect you to have a lot more post operative sensitivity after the bleaching process.

Some people are at a higher risk of sensitivity from whitening

There is a subset of individuals who will most likely experience more severe sensitivity from teeth whitening and it is as you probably guessed. It is those people who already have sensitive teeth year round. These people typically have gum recession either around the whole mouth or the gum has receded in just a couple of places.

These recession spots are more sensitive than the rest. Common symptoms would be if they feel a tingle whenever they drink something cold or to any sort of temperature that is not room temperature.

Another group of people who may be extra sensitive would be those who indulge in a more acidic diet. They may like drinking lemon water or eat a lot of acidic foods. The health conscious ones who use acidic salad dressings would be what comes to our mind.

The reason they are more sensitive is because the low pH foods, the acidity can dislodge the smear plugs. This will cause the dentinal tubules to actually widen over time because the acid will demineralize the teeth. Infographic below:

When the tubules enlarge, it becomes more difficult for the smear plugs to clog them. Also since they are bigger, it will let in more stimuli.

Recommendation would be to use Sensodyne toothpaste year round and also to decrease the acidic dietary habits as much as possible!


Overall, there will be a good chance your teeth will be killing you after teeth whitening just because that is a natural consequence of what happens when the peroxide gel touches your teeth. The sensitivity will just be a side effect that you should be well aware of. What we can do is try to minimize it by using various desensitizers because we don't want to keep you from having pearly whites!

If you're interested in the KoR, please book an appointment with one of our long island city dentists. It is currently the most effective product on the market! They also have the best desensitizer! Some whitening products don't even come with any desensitizing...

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