Dentin hypersensitivity is a condition which makes it unpleasant to drink cold beverages and eat acidic foods. There have been many proposed modalities in treating this sensitivity but did you know that fluoride is effective in reducing the symptoms?
Well to be clear, simply brushing with your sodium fluoride toothpaste isn’t quite enough to elicit the desired effects. You will need to see your dentist for a professional application of fluoride varnish.
The varnish is still sodium fluoride except it comes in a 5% solution that can stick onto the surfaces of your enamel for hours. This is in contrast to your toothpaste which typically comes in a 0.25% sodium fluoride concentration. The fluoride varnish is essentially 20x more concentrated than your fluoridated toothpaste.
Are you curious as to why you get dentin hypersensitivity and why a concentrated formulation of sodium fluoride helps alleviate it? We’re going to teach you everything that you need to know about fluoride and teeth sensitivity!
Dentin hypersensitivity mechanism
The exact mechanism for how dentin hypersensitivity occurs has yet to be proven even with all of the advances in technology. However the current most widely accepted theory for it is by Brannstorm called the Hydrodynamic Theory.
The hydrodynamic theory states that dentin hypersensitivity is a result of fluid movements in the intertubular dentin. The baroreceptors can sense a change in fluid whenever the tooth is subjected to stimuli. This results in an action potential being generated, which tells us that we’re feeling pain.
Potential causes for dentinal fluid movements:
- Thermal changes such as drinking or consuming hot and cold foods.
- Physical changes such as brushing your teeth.
- Osmotic gradients such as bleaching your teeth.
Direction of fluid movements when subjected to stimuli:
- Fluids move away from the nerve – Cooling, drying, evaporation, and hypertonic chemical stimuli such as teeth whitening
- Fluids move towards the nerve – Heat and probing.
Proposed treatment modalities for alleviating the hypersensitivity
The two most common ways to treat dentin hypersensitivity is by desensitizing the nerve or occluding the dentinal tubules.
Desensitizing the nerve usually involves utilizing potassium nitrate which renders the nerve endings unexcitable. It basically prevents it from generating action potential despite the onslaught of offending stimuli. Most sensitivity toothpastes will have it and one of the most common ones is Sensodyne.
Occluding the dentinal tubules require an agent that will form a precipitate that can block off the entrances to tubules. Since the tubules are no longer patent the tooth will not be able to respond to any stimuli. There will be no more fluid movements since they’re no longer exposed to the external environment.
Some toothpastes will utilize stannous fluoride instead of potassium nitrate. The stannous fluoride will occlude the tubules while the potassium nitrate will desensitize the nerve. The one downside to the stannous fluoride is its potential teeth staining.
How sodium fluoride reduces sensitivity
Sodium fluoride does not possess the ability to desensitize the nerve but what it can do is occlude the dentinal tubules instead.
Sodium fluoride (NaF) is able to occlude the tubules by forming calcium fluoride (CaF2) precipitate on the surface of the enamel. Studies have shown via a SEM (scanning electron microscope) that it forms a globule of calcium-fluoride like material .
The first effect of this CaF2 layer is that it can penetrate into the tubules and effectively seal it off.
The second effect is that it actually forms a barrier that further protects the tooth by attracting phosphates (PO4). Together the calcium fluoride and phosphates create a protective layer along the surface of the enamel. Extended exposure to saliva will form a fluorapatite layer over the calcium fluoride layer.
This additional layer prevents stimuli from reaching the tooth and causing fluid movements in the dentinal tubules. It also acts as a reservoir for calcium, phosphate, and fluoride ions whenever the tooth experiences an acid attack. Essentially it will break down first but then provide the building blocks for the tooth to remineralize.
To summarize, sodium fluoride forms calcium fluoride which attaches to the surface of the tooth. Then the calcium fluoride will attract phosphate and actually form an extra layer of fluorapatite protection over the enamel. All of these minerals will occlude the dentinal tubules in addition to forming an additional barrier over the tooth to protect it from stimuli.
How does calcium fluoride even form?
The fluoride varnish application is actually just pure sodium fluoride. There is no calcium nor phosphates in it but yet studies have shown that all of this can form in the mouth!
The answer to that lies in the composition of our saliva:
- Sodium
- Potassium
- Calcium
- Magnesium
- Bicarbonate
- Phosphates
- Immunoglobulins
- Proteins
- Enzymes
- Mucins
- Urea
- Ammonia.
Saliva has a lot of functions but the one that we’re concerned about is its ability to remineralize a demineralized tooth structure. The calcium, phosphate, and proteins work together as an anti-solubility factor which assists in remineralization.
Essentially the fluoride ion interacts with the calcium and phosphates in our saliva to form this new protective barrier. That is how it desensitizes our teeth.
Only concentrated sodium fluoride has been shown to have anti-sensitivity effects
Unfortunately the concentration of sodium fluoride in your toothpaste isn’t quite sufficient in causing a desensitizing effect. In order to form the calcium fluoride (CaF2) that is loosely bound to your enamel, requires 100-10,000 ppm of F to achieve it. Only fluoride varnish which is 20x more concentrated than your fluoridated toothpaste is able to reach those levels.
This article in the Journal of the American Dental Association, compared various 5% fluoride varnishes and their anti-sensitivity effect. All of them were effective in reduced sensitivity but none of them were different from one another. In other words, they were all equal in efficacy.
Another randomized double-blind control study found 5% sodium fluoride to be effective in reducing dentin hypersensitivity. In fact, after 3 applications, the anti-sensitivity effect appears to have gradually improved all the way up to the 8 week mark.
What that means is that using fluoride varnish can be a potential treatment with long term effects. Aside from that there is one other aspect which makes the varnish so efficacious. It is the fact that it comes in a very sticky gel that adheres to the surface of your teeth. That allows your teeth to absorb all of the topical fluoride!
Takeaway
Sodium fluoride has been proven to reduce dentin hypersensitivity when it is administered in a high concentrations only. This is usually done via a fluoride varnish which delivers the fluoride in a sticky gel that adheres to our teeth.
If you don’t eat or drink for the next 4 hours after application, it will give your teeth plenty of time to soak in all of that topical fluoride. You’ll not only prevent cavities but also reduce teeth sensitivity.
Nonetheless, if you feel like you still need help in reducing dentin hypersensitivity we do have a guide on how to stop sensitive teeth pain immediately.