Dentin hypersensitivity is a very common condition with studies showing a prevalence of affecting 3-98% of the population. The statistics may vary depending on which population you’re examining but the point is that it’s quite common.
This is important because dentin hypersensitivity means that the individual will feel discomfort due to various stimuli.
- Tactile stimulus – when you’re brushing or if food touches the surface.
- Cold stimulus – when you drink cold beverages or eat cold foods.
- Air stimulus – breathing in air can cause discomfort to your teeth.
Due to how uncomfortable the condition may be, it has led to much research on how to treat it. Our focus today will be nerve desensitization, which is one way to treat dentin hypersensitivity.
The mechanism of dentin hypersensitivity
The mechanism for dentin hypersensitivity has not yet been proven. However the current most widely accepted is the Hydrodynamic Theory which was first proposed by Brannstrom.
The theory states that it is due to the movement of fluids within the dentinal tubules that ultimately results in pain. There are baroreceptors which can sense the change in fluids whenever the tooth is exposed to a stimulus. If they sense fluid movement, it will elicit a an action potential thus leading to perceived pain.
Causes for dentinal fluid movements:
- Thermal changes such as hot and cold.
- Physical changes.
- Osmotic gradients.
Direction of fluid movements:
- Away from the nerve – Cooling, drying, evaporation, and hypertonic chemical stimuli such as teeth whitening
- Towards the nerve – Heat and probing
Current treatment modalities
According to research from the Journal of Conservative Dentistry, there are a variety of treatments to manage dentin hypersensitivity. Nerve desensitization is just one of the many treatments that are available. The mechanism in how each of them work may differ.
- Potassium nitrate
- Silver nitrate
- Zinc chloride
- Strontium chloride hexahydrate
Plugging dentinal tubules
- Sodium fluoride
- Stannous fluoride
- Strontium chloride
- Potassium oxalate
- Calcium phosphate
- Calcium carbonate
- Bio active glasses (SiO2–P2O5–CaO–Na2O)
Dentine adhesive sealers
- Fluoride varnishes
- Oxalic acid and resin
- Glass ionomer cements
- Dentin bonding agents
- Neodymium:yttrium aluminum garnet (Nd-YAG) laser
- GaAlAs (galium-aluminium-arsenide laser)
- Erbium-YAG laser
How does nerve desensitization work?
Currently the only substance that is capable of desensitizing the tooth nerve directly is potassium nitrate (KNO3). Unfortunately the mechanism for how it works has not been definitively proven.
Currently, the accepted proposed mechanism for how potassium nitrate works is by making the nerve endings unexcitable. It renders it unable to generate an action potential.
Since it is composed of potassium ions (K+) and nitrate ions (NO3–), it supplies an overabundance of potassium to the nerve endings. The excessive amount of K+ disrupts the normal concentration gradient, thus preventing an action potential from generating.
How action potentials are generated under normal circumstances:
Molecules typically move from an area of high concentration towards a low concentration. It will not move in the reverse direction.
- Depolarization – When the sodium channels open, the Na+ flows from the extracellular matrix to the interior.
- Repolarization – This results in the potassium channels opening, the K+ flows from the intracellular matrix to the exterior.
- Action potential is generated.
- High Na
- Low K
- Low Na
- High K
Since potassium nitrate contains a lot of potassium ions, it changes the extracellular matrix concentration from low to high. This change in concentration disrupts the normal concentration gradient thus preventing K+ from flowing outwards. The action potential is effectively prevented from firing.
Potassium nitrate toothpastes
If you’re looking for a product that can desensitize your nerve, you will need a potassium nitrate toothpaste. The vast majority of anti-sensitivity dentifrices will utilize potassium nitrate as its main desensitizer.
Usually if the toothpaste says “sensitive” on it, it most likely has the ingredient within it. The most prominent brand of sensitive toothpastes would be Sensodyne since it already has the word embedded within its name.
However you should be aware that not all Sensodyne products utilize potassium nitrate. Some of their toothpastes will use stannous fluoride in lieu of it so you must read the ingredients carefully if you’re specifically looking for nerve desensitization.
- Potassium nitrate will desensitize the nerve.
- Stannous fluoride will occlude the dentinal tubules.
Nevertheless, all of the Sensodyne products do work. It just comes down to what you’re looking for. An advantage that potassium nitrate has over stannous fluoride is that it does not result in teeth staining.
Related content: What does fluoride do for your teeth.
How long does it take to desensitize the nerve?
According to Haleon, the makers of Sensodyne toothpaste it takes up to 2 weeks before the nerve gets desensitized. This is with brushing twice a day. An important point to note is that the desensitization will gradually build and improve even more if you continue to use it. That means the peak effect is well beyond the two week mark.
Side comment: You may not be familiar with Haleon but they were recently spun off from GlaxoSmithKline (GSK) in mid 2022. You’re probably familiar with GSK but this explains the name change.
Research supporting efficacy
According to a study in the Journal of Clinical Periodontology, there was a rapid decrease in dentin hypersensitivity after 2 weeks. However sensitivity relief continued to improve at the 4, 8, and 12 week mark. At the 12 week mark, 67% of participants reported complete sensitivity relief.
This confirms that you should expect about 2 weeks for you to start seeing effects from potassium nitrate. Although you should also expect the symptoms to continue to improve over the next 12 weeks of continued use.
That makes sense because it takes time for the potassium nitrate to diffuse to the nerve endings. It also means that it takes time for it to build up to a sufficient concentration for it to start exerting effects on the nerve.
According to a study by Peacock, there was a concentration threshold to start seeing nerve desensitization effects.
- An effect was seen when the K+ concentration was in the 8-64 mmol/L range.
- A complete desensitization was observed at 32 mmol/L.
Is the desensitization permanent?
According to Sensodyne, if you stop using their toothpaste with potassium nitrate, the sensitivity may return.
If you stop brushing with Sensodyne toothpaste, your sensitivity can return, so it is best to make Sensodyne your daily toothpaste to get long-lasting relief.Source
This means that it only works while you keep using it. Once you stop, the effects will most likely start to dissipate. Due to this reason, we tell all of our patients who do use potassium nitrate toothpastes that it is literally a life time sentence. Once you start, you can’t stop using it!
One way to treat dentin hypersensitivity is by desensitizing the nerve with potassium nitrate. Fortunately, most sensitivity toothpastes do utilize KNO3 which means that all you need to do is simply buy it and start brushing with it twice a day.
It may take a minimum of at least 2 weeks for you to start seeing reduced dentin hypersensitivity. Then with continued use, you should see it improve even further over the next 12 weeks. However once you stop using it, the effects will dissipate.
If you wanted to learn more, we do have a guide on how to stop sensitive teeth pain immediately.