Sensitive toothpastes work either by occluding exposed dentinal tubules or by depolarizing the tooth nerve to provide temporary relief for teeth sensitivity. The desensitization mechanism can be better explained if you understand why teeth get sensitive.
Table of contents:
Why teeth get sensitive
Absent of any tooth decay or infection, teeth can become sensitive from exposed dentinal tubules that become unclogged. These tubules are filled with nerve endings that can trigger sensitivity, discomfort, and pain when stimulated by external stimuli.
External stimuli triggering sensitivity:
Cold
Hot
Sweet
Sour
Acidic
Spicy
The mechanism for why we feel discomfort can be explained by Branstrom's theory of dentinal hypersensitivity. The theory states that receptors can elicit pain signals when they sense fluid movement within dentinal tubules due to external stimuli. It can sense when fluids are pulled away from the nerve or when fluids are pushed towards the pulp.
External Stimuli | Dentinal Tubule Fluid Movement |
|---|---|
Cold | Away from the nerve |
Drying | Away from the nerve |
Evaporation | Away from the nerve |
Hypertonic solutions | Away from the nerve |
Heat | Towards the pulp |
Probing | Towards the pulp |
In summary, the dentinal tubular fluid movements trigger pain and sensitivity signals.
Normal teeth vs Sensitive teeth
Why normal teeth don't get sensitive
For normal teeth, the fluid movements are minimized due to the presence of smear plugs and adequate gingival coverage.
Smear plugs. The smear plugs naturally occlude the dentinal tubules thus minimizing or even preventing stimuli from interacting with the fluids inside. No fluid movements mean no discomfort. These plugs are our body's natural defense mechanism against sensitivity.
Gum coverage. In addition to the smear plugs, our gums cover over the root surfaces of teeth thus providing an extra layer of insulation.
Therefore you can think of your mouth as having two protective mechanisms against teeth sensitivity. The smear plugs block the opening of the tubules and then the gums cover over the entire surface as extra protection.
Sensitive teeth
Those who experience chronic teeth sensitivity will often have missing smear plugs with enlarged dentinal orifices or gum recession. The unfortunate ones will have a combination of both which can really impact the quality of life.
These two factors put you at greater risk for dental sensitivity.
Other reasons for teeth sensitivity
The scenario above describes individuals who experience symptoms from gum recession and otherwise healthy teeth. However, there are other dental conditions with symptoms of dentinal hypersensitivity.
Oral conditions with sensitivity as a symptom:
Tooth decay. Decayed teeth will have cavities which are literally holes in your teeth. Thus, cavities readily allow stimuli to affect dentinal tubular fluid movements.
Infection. A tell tale sign of a tooth nerve infection would be lingering sensitivity to cold.
Defective restorations. A cracked or broken filling will leave your tooth nerve exposed. Exposed tooth structure that is not covered nor protected will be sensitive.
Fractured teeth. A broken tooth is certainly unhealthy and if sensitivity is all that you're feeling, you should consider yourself lucky. Excruciating pain is actually the norm!
If your teeth are sensitive from any of the above conditions, brushing with anti-sensitivity toothpaste won't help at all. All of these require professional treatment from a dentist such as cavity fillings, root canals, extractions, and etc.
Please schedule a consultation with your dentist as promptly as possible because at home remedies will not work
How does sensitive toothpaste work?
Sensitive toothpastes work because they contain a desensitizing agent which can occlude exposed dentinal tubules or depolarize tooth nerves.
Tubular occlusion. A tubular occlusion desensitizing agent will clog or block the exposed openings of dentinal tubules. This prevents stimuli from interacting with the tooth nerve.
Nerve depolarization. A nerve depolarization agent renders the tooth nerve unexcitable. That means your tooth still feels the stimuli but the nerve just won't fire a pain signal.
Put another way, the tubular occlusion agents act as a physical barrier thus preventing stimuli from contacting the nerve. The nerve depolarizers act as a tooth numbing agent, similar to how novocaine lets your dentist drill on your tooth without you feeling any pain.
Tubular occlusion desensitizing agents:
Stannous Fluoride
Stannous chloride
Nano-hydroxyapatite
Strontium Chloride
Arginine
Nerve depolarization desensitizing agents:
Potassium Citrate
It is important to understand which desensitizing agent is in your toothpaste because if it isn't working, you may want to try a different one. That could be the key to the relief that you've been searching for.
Without further ado, let's dive into all of these different types of desensitizing agents in your toothpaste and how they work.
Potassium Nitrate
Potassium nitrate (KNO3) also known as saltpeter renders the tooth nerve unexcitable when it builds up to a sufficient concentration.
Toothpastes with KNO3:
Sensodyne pronamel
Colgate sensitive original
Hello sensitivity relief
Ollie hydroxyapatite toothpaste
How potassium nitrate desensitizes teeth:
Supplies an overabundance of potassium ions (K+) to the tooth nerve.
Excessive potassium causes a reversal of the concentration gradient.
Inverted concentration gradient prevents action potential generation aka no sensitivity signal gets sent to your brain.
The key point we wish to emphasize is that the desensitizing effect occurs only when there is a sufficient concentration of potassium. According to the makers of Sensodyne, it takes about two weeks of consistent brushing for the KNO3 to build up to a sufficient concentration.
Mechanism for action potential generation
Under normal circumstances without KNO3 interference, there is a natural concentration gradient for potassium and sodium. All molecules move down their gradient from a higher concentration towards a lower one and it never moves in the reverse direction.
Extracellular concentration:
High Na
Low K
Intracellular concentration:
Low Na
High K
How an action potential is generated:
Upon stimulation, sodium rushes into the cell thus causing depolarization.
Consequently, potassium rushes out of the cell thus causing repolarization.
Combination of these two events generate an action potential which is effectively how our brain receives the sensitivity signal.
How potassium nitrate blocks the action potential generation is by reversing the potassium gradient. It makes the extracellular concentration of potassium higher than it's intracellular concentration.
This prevents the cell from repolarizing since the potassium can't flow out. Thus, the nerve cell is unable to complete all of the required steps to send a pain signal.
Potassium citrate
Potassium citrate is another nerve depolarizing desensitizer. It works near identical to potassium nitrate in that they both supply an overabundance of K+ ions which renders the pulp inexcitable.
Some of the trendier toothpastes will use this in lieu of KNO3 but for all intents and purposes they work the same. Their efficacy are also equivalent.
Stannous fluoride
Stannous fluoride (SnF2) occludes patent dentinal tubules thus effectively preventing stimuli from interacting with the fluids of the tooth nerve.
Examples of SnF2 toothpastes:
Colgate total
Crest pro-health
Sensodyne rapid relief
Essentially stannous fluoride works by recreating the missing smear plugs and reclog all of the open tubules. With the orifices closed and blocked off, less of the stimuli will be able to interact with the components within the tubules.
Basically the tooth nerve will be shielded from all external stimuli. It is akin to having a protective barrier that shields the tooth.
Mechanism for SnF2 tubular occlusion
Stannous fluoride is a form of fluoride that is stabilized by Tin (Sn). The desensitizing effect is solely derived from the tin and not from the fluoride. Are you surprised?
A study from the Journal of the American Dental Association, found that stannous fluoride toothpaste significantly reduced hypersensitivity after 8 weeks.
The tubules were occluded with a deposit consisting of tin, zinc, phosphate, and silicon.
Stannous fluoride occluded 82% of the open tubules vs the placebo's 35%.
In summary, the newly created smear plugs were a tin mixture composed of zinc, phosphate and silicon. This metallic complex possesses the ability to occlude the exposed tubules.
In case you were curious, we've written an article comparing stannous fluoride vs potassium nitrate. Which one is superior in providing sensitivity relief? Read to find out more.
Nano-hydroxyapatite
Nanohydroxyapatite (nHap) will desensitize teeth by occluding open dentinal tubules, which makes it work in a similar way to stannous fluoride.
Examples of nHap toothpaste:
Davids sensitive & whitening toothpaste
Risewell mineral toothpaste
Boka ela mint toothpaste
Ollie toothpaste
Dr Jen super paste
Essentially nano-hydroxyapatite toothpastes work by directly clogging all of the orifices of open dentinal tubules. By occluding the orifices it prevents external stimuli from interacting with the tubular components. Since there is no interaction, no nerve signals are fired.
Studies have shown that it is effective enough to reduce teeth sensitivity after whitening sessions. We all know that the teeth become extremely sensitive after bleaching and if it works for that it will work for your everyday symptoms.
Mechanism for hydroxyapatite tubule occlusion
The nano-hydroxyapatite is a smaller version of the very same tooth mineral that your enamel is made of, hence the "nano" in front of the name. Since they're identical substances, the nHap simply inserts itself into all of the tubules' orifices.
Therefore instead of having smear plugs, the hydroxyapatite will serve as a replacement. This is even better because it's similar to having extra enamel.
Hydroxyapatite vs Stannous fluoride effectiveness:
nHap is more effective than stannous fluoride because it can form an additional protective layer after plugging the dentinal tubules.
SnF2 requires tin to form a complex with other molecules before it can plug the tubules. Hydroxyapatite can directly insert itself into the tubules without any assistance.
Strontium chloride
Strontium chloride is yet another dentinal occlusion desensitizing agent. Studies have shown it to be effective in reducing sensitivity.
We would love to give you examples of brands that use strontium chloride but unfortunately we couldn't really find any. As far as we know, there is no toothpaste formulation with it that is available in the United States.
Historically, it was present in the original Sensodyne toothpaste back in 1961. However according to the timeline on their website, strontium chloride seems to have been mostly replaced by potassium nitrate by the 1980s.
We browsed through every product offering from Sensodyne but to no avail. There isn't a single product line that still uses strontium chloride. We are unsure why it was discontinued because the studies did show that it was effective in reducing sensitivity. Perhaps the potassium nitrate was just a superior product?
Arginine
Arginine based toothpastes will reduce teeth sensitivity by occluding open dentinal tubules. Therefore it works in a similar manner as stannous fluoride, nano-hydroxyapatite, and strontium chloride.
The only toothpaste that we are aware of that uses arginine is Colgate pro-relief and they call it Pro-Argin. This toothpaste is actually NOT available in the United States. It is currently only available for purchase overseas such as in Europe and Asia.
Historically, it used to be available in the US but for some reason they ceased distribution here. We've inquired with Colgate before and they didn't give us a reply. They merely said that they'll pass on the message that we liked their product.
How to use sensitive toothpaste effectively
Here are some tips on how to maximize the desensitizing effect of your sensitive toothpaste.
2 mins brushing minimum. Toothpaste desensitizers work via contact time. If you don't brush for the recommended two minutes, you're not getting the full effect.
Brush towards gum line. Most of the tooth sensitivity is at the gum line where recession is common. That is the area that you want to be applying the toothpaste. If you don't brush at the sensitive area then what exactly are you desensitizing?
Don't rinse out after brushing. Spit out after you're done brushing but don't rinse. Refraining from rinsing will allow the desensitizing agent to work for a longer period of time. Rinsing will dilute and wash away the desensitizer thus decreasing its efficacy.
Brush twice a day or more. The more you brush with the toothpaste, the more time you allow it to work. You should really be brushing after every meal in order to get the maximum effect.
Hopefully you've been implementing these tips the whole time and it wasn't the first time that you've heard of it.
Can you use this type of toothpaste everyday?
Sensitive toothpaste is meant to be used every single day for the rest of your life.
Brush teeth thoroughly for at least 1 minute twice a day (morning and evening), and not more than 3 times a day, or as recommended by a dentist or doctor. Make sure to brush all sensitive areas of the teeth. Minimize swallowing. Spit out after brushing.
The reason is because brushing with it does not permanently cure teeth sensitivity. The toothpaste can only help you manage the symptoms. According to Sensodyne, once you stop using it the effects will cease and the sensitivity will return.
We are unsure about why Sensodyne is even stating that you should brush for at least 1 minute. The general consensus is to brush for at least 2 minutes twice a day and that is according to the ADA.
How long does it take for sensitive toothpaste to work?
Depending on which desensitizing agent is in your toothpaste, the relief may be immediate or it could take up to 2 weeks for it to work. Overall you can expect these toothpastes take between 1-14 days for it to starting alleviating your symptoms.
How long it takes to work according to research:
Potassium nitrate: Studies have shown that it may take up to 2 weeks for you to see results with the symptoms continuing to improve for up to 12 weeks.
Stannous fluoride: Studies have shown that a desensitizing effect was present after a single day of use.
Nano-hydroxyapatite: Studies have shown that symptoms were reduced after using for a day.
Based on the data above, the tubular occlusion desensitizers such as stannous fluoride and nanohydroxyapatite can work as fast as 1 day. The nerve desensitizer, potassium nitrate will take longer to work because it may take about 2 weeks for it to show an effect.
What to do when sensitive tooth doesn't work
If you're already using a desensitizing toothpaste but your teeth are still sensitive, it could be due to a number of causes and not necessarily that the sensitive toothpaste doesn't work.
Not brushing long enough. Are you brushing the full two minutes?
Wrong desensitizer. Perhaps the desensitizing agent isn't right for you.
Not brushing towards gum line. If you're not applying the toothpaste towards the most sensitive spot, it won't work.
Excessive acidic food consumption. Acidic foods will undo the desensitizing effects which is why you have to continually use the toothpaste!
Aggressive brushing. Hard handed brushing can cause the gums to recede more.
Peroxide based toothpaste. Hydrogen peroxide is used to whiten teeth, if your toothpaste contains it you may be causing sensitivity unknowingly!
What you can try if the toothpaste doesn't work:
Use a timer to ensure you're brushing the full two minutes.
If you're using a nerve depolarizing agent, try switching to a tubular occlusion one instead. The vice versa would also be true.
Be cognizant of brushing towards the gum line so you're effectively applying toothpaste at the most sensitive spots.
Reduce the amount of acidic foods you eat and drink.
Use a soft toothbrush and brush more gentle to prevent gum recession.
Avoid whitening toothpaste.
How long does it take for sensitive toothpaste to work?
Depending on which desensitizing agent is in the particular sensitive toothpaste that you're using, the relief may be immediate or it could take 2 weeks. On average these toothpastes take 1-14 days for it to starting alleviating the symptoms.
Potassium nitrate - Studies have shown that it may take up to 2 weeks for you to see results. The symptoms continued to improve up to the 12 week mark.
Stannous fluoride - Studies have shown that a desensitizing effect was present after a single day of use.
Nano-hydroxyapatite - Studies have shown that symptoms were reduced after using for a day.
Based on the data above, the tubular occlusion desensitizers such as stannous fluoride and nanohydroxyapatite can work as fast as 1 day. The nerve desensitizer, potassium nitrate will take longer to work because it may take about 2 weeks for it to show an effect.
Nonetheless, that is just the time it takes for the toothpastes to start working.
Takeaway
Depending on the desensitizing agent in the sensitive toothpaste, the mechanism via how it works will be different. Basically these toothpastes can be divided into two categories. They either reduce sensitivity by tubular occlusion or by desensitizing the nerve.
Both of them will work but perhaps one works better for you than the other. It is important for you to know exactly how your toothpaste works because if your product is not working, you should try the other one. FYI, there is no toothpaste that contains both potassium nitrate and stannous fluoride.
