To the general populace, a toothpaste either has fluoride or it doesn’t but that is a blanket statement. Fluoride comes in more than one form and depending on which type, it can have different effects on your mouth.
These are the two most common types of fluoride found in toothpaste that we’ll be comparing today:
- Stannous fluoride (SnF2)
- Sodium fluoride (NaF)
There is so much more than what meets the eyes and it would behoove you to understand the differences and similarities between the two. We’re going to do a deep dive into both forms of fluoride. By the end of this article, you’ll be looking carefully at the ingredients in your toothpaste just to find out what is in it and what it can do for you.
Perhaps you’re also looking to see what it is not doing for you… In that case, a product switch may be in order.
Similarities between sodium fluoride and stannous fluoride
The commonality between stannous fluoride and sodium fluoride is the effects that fluoride has on your teeth. The difference is that they both contain the fluorine ion (F–) but they’re bonded to a different element. Aside from that the F will exert the same effects regardless of which form of fluoride it is.
- Stannous fluoride is bonded to Sn (Tin)
- Sodium fluoride is bonded to Na (Sodium)
What does fluoride do for teeth?
Fluoride prevents cavities primarily via a topical effect which includes:
- Inhibition of demineralization
- Enhancement of remineralization
- Inhibition of bacterial activity in plaque
All of these effects are highly relevant for toothpastes which contain it since brushing it on teeth is applying it topically. None of the toothpaste is being swallowed or consumed so it is not a systemic effect.
Fluoride inhibits demineralization
Fluoride is able to inhibit enamel demineralization via two mechanisms:
- Firmly bound fluoride in the form of fluorapatite is more resistant to demineralization.
- Loosely bound fluoride in the form of calcium fluoride-like layer which dissolves first acting as a sacrificial layer.
Tightly bound fluoride in fluorapatite
Fluoride can replace the hydroxyl group of hydroxyapatite in enamel and convert it to fluorapatite. This results in a more stable and stronger structure.
Benefits of converting hydroxyapatite to fluorapatite:
- Increased resistance to acid dissolution.
- Decreases mineral solubility.
- Increased stability of mineral structure.
- Promotes remineralization to reverse cavities.
The most obvious effect is the change in critical pH when it transforms from hydroxyapatite to fluorapatite. The critical pH level is when each respective structure begins to demineralize and dissolve.
- Hydroxyapatite = 5.5 pH
- Fluorapatite = 4.5 pH
The reduction in fluorapatite’s critical pH level means that it can withstand stronger acids before it begins to demineralize. Essentially it becomes more resistant to demineralization forces.
Loosely bound calcium fluoride-like layer
Topically applied fluoride from toothpaste can form a loosely bound calcium flouride-like layer over the enamel. It isn’t pure calcium fluoride since the layer does attract phosphates to it. This is different from the firmly bound fluoride.
There are several benefits to having this layer:
- It dissolves first under acid attack.
- Serves as a reservoir for calcium, phosphates, and fluoride
Since this layer covers the enamel, it becomes the first to dissolve under acidic conditions. It serves as a protective sacrificial layer in doing so.
The benefits don’t stop after it dissolves because when it does, it releases calcium, phosphates, and fluoride. The phosphate can help buffer the acidity of the oral environment and also act as a remineralizing agent as well.
Fluoride enhances remineralization
In addition to inhibiting demineralization, fluoride also enhances remineralization of the enamel. Yes, you can reverse cavities with it.
- Carious lesions readily take in more fluoride than sound enamel.
- Calcium fluoride-like layer provides a reservoir of minerals for remineralizing.
Studies have shown that demineralized parts of the enamel will incorporate and draw in fluoride more readily than intact enamel. This means that the diseased structures have a propensity to repair itself in the presence of fluoride.
As long as you brush twice a day with fluoridated toothpaste, you should have a steady supply of fluoride in your mouth. This can often lead to the formation of a calcium fluoride like layer over your enamel, which can aid in remineralization.
Whenever an acid attack occurs, the sacrificial layer disintegrates and releases calcium, phosphates, and fluoride. Your tooth could then use these very same minerals to remineralize itself.
Related content: How to remineralize teeth.
Fluoride inhibits bacterial activity within plaque
The antibacterial effects of fluoride has been well established but there has been much disagreement on its anti-cavity effect. Despite the non-consensus, these are the two effects which fluoride directly has on bacteria.
- Inhibits carbohydrate metabolism (glycolytic enzyme enolase activity) – sugar metabolism
- Inhibits proton-extruding adenosine triphosphate (H+/ATPase) – molecular transport
Essentially what the fluoride does is interfere with the bacteria’s ability to process sugar and also transport of sugar and other molecules into/out of the cell.
Inhibits glycolytic enzyme enolase’s activity
Fluoride inhibits the activity of the enzyme enolase, which ultimately affects the metabolism of sugar and the uptake of it from its surroundings. Essentially what happens is the bacteria loses its ability to process sugar and to take in sugar from the mouth.
Mechanism for how this occurs:
- Enolase converts 2-phosphoglycerate to phosphoenolpyruvate (PEP). This is important because this is the second to last step for the conversion of glucose to pyruvate.
- PEP is used as an energy source for the phosphotransferase system (PTS). The PTS is used by bacteria to transport sugar from outside of the cell to inside.
To summarize: Fluoride blocks the metabolism of glucose and it prevents the intake of glucose from outside the cell.
Fluoride can inhibit the transmembrane bound H+/ATPase, which is used to transport solutes across the membranes.
What H+/ATPase does:
- It establishes a proton gradient in the cell by pumping protons out of the cell.
- It uses ATP as an energy source.
What fluoride also does is diffuse into the cell as HF but then it dissociates into H and F. This in effect worsens the pre-existing proton gradient. The purpose of the H+/ATPase is to pump protons out of the cell but fluoride is bringing protons into the cell. In addition to that, it prevents the H+/ATPase from working.
The ultimate effect is that the cell is unable to transport necessary solutes into and out of the cell since there is no concentration gradient.
Differences between stannous fluoride and sodium fluoride
Stannous fluoride has a couple of additional benefits over the sodium fluoride. Most of the effects seem to stem from the tin that is in SnF2.
- Anti-bacterial – It is both bacteriostatic and bacteriocidal.
- Improves gum health by reducing gingivitis, gum bleeding, plaque, and bad breath.
- Reduces teeth sensitivity.
Sodium fluoride does not have any particular advantage over its stannous counterpart. However it does acquire the ability to reduce dentinal hypersensitivity when it is applied in a concentrated solution such as in fluoride varnish.
Stannous fluoride’s effects
Studies have shown stannous fluoride to be anti-bacterial where it can inhibit their growth but it can also kill them at a high enough concentration. This study was performed on one of the primary cavity causing bacterias, streptococcus mutans.
- Sodium fluoride arrested growth at 300 and 600 ppm
- Stannous fluoride suppressed the rate of growth at 75 ppm and showed some bactericidal activity at 150 and 300 ppm.
- SnF2 was totally bactericidal at 600 ppm.
The conclusion that we can draw from this research is that both types of F have anti-bacterial characteristics but the SnF2 is significantly more potent. Other studies have also validated that claim where they also found stannous fluoride to be much more potent than the sodium version.
The explanation for this difference in anti-bacterial potency has to do with the tin in stannous fluoride. Studies have found that this unique effect is largely to do with the increased uptake of tin in the bacteria.
Consequences of SnF2 being bacteriostatic and bacteriocidal
Since stannous fluoride excels on managing the growth and population of bacteria, it brings some wonderful benefits for the mouth. Studies have shown over a 6-month period there were statistically significant reductions in gingivitis, gingival bleeding, and plaque.
That may be explained by the fact that stannous fluoride can kill 90% to 99% of the salivary microbes 16 hours after a single exposure. Now imagine the protective benefits that can occur if you brush with it in the morning and at night time!
SnF2 can reduce sensitivity in teeth
Unlike sodium fluoride, SnF2 has an innate desensitizing effect on teeth by occluding all open dentinal tubules. The reason it can do this is because the tin can form a complex with zinc, phosphate, and silicon which plugs up the tubules.
Since NaF does not have tin in it, it is unable to occlude the dentinal tubules. That is unfortunate because this desensitizing effect is fairly significant. Studies have shown that stannous fluoride does decrease sensitivity, which is statistically significantly more than sodium fluoride.
Sodium fluoride’s effect
Stannous fluoride is able to desensitize teeth while in toothpaste form but sodium fluoride cannot. However there is one exception and that is if you apply a concentrated version of NaF such as in fluoride varnish.
Studies have shown that 5% sodium fluoride in varnish form does possess the ability to desensitize teeth. That is significantly more concentrated than your average 0.25% sodium fluoride in toothpaste. Essentially, it requires about 20x the concentration of fluoride as your toothpaste in order to get that anti-sensitivity effect.
Due to the concentration requirement, we are hesitant to say that sodium fluoride based toothpastes have a desensitizing effect. That is consistent with how none of the manufacturers list it as a dentifrice for sensitive teeth. However the toothpastes with stannous fluoride do claim it can desensitize your teeth!
Is one of them more toxic?
Both types of fluorides in toothpaste formulation are safe to use when used properly. As with all toothpastes, there is a warning label on it which says to get medical help or contact poison control immediately if you swallow it.
Therefore as long as you’re not trying to eat toothpaste, it is safe to use for brushing your teeth on a daily basis. This is typically not an issue for adults but for small children, you may want to keep a close eye on them while they’re learning to brush.
Why did Colgate switch to stannous fluoride?
Colgate has recently started producing toothpastes with stannous fluoride because of the additional benefits that it has over sodium fluoride.
- Desensitizes teeth
- Improves gum health by reducing bleeding and plaque
Despite us saying that they recently started making toothpaste with SnF2, it has actually been around since the 1950s. Proctor & Gamble was the company who patented it and consequently it became the first ADA approved toothpaste. The first stannous fluoride toothpaste was called Crest.
Although it has been in existence for more than half a century, it wasn’t widely adopted due to its teeth staining potential. Studies found that a yellow-golden stain formed on teeth when used with it long term.
In addition to the staining, the toothpaste also had a metallic taste associated with it. That was purely due to the fact that fluorine (F) was bound to tin (Sn). It had a tendency to react with orange juice and make it taste bitter.
Nonetheless, the resurgence of stannous fluoride in toothpaste came because manufacturers found a way to reduce the staining and taste of it. In that study, they found that the new Colgate Total stannous fluoride formulation had reduced stains. (Crest also found a way to reduce these adverse effects from as early as 2004).
Essentially, the recent advances in technology have allowed toothpaste companies to bypass these unwanted side effects. They’ve managed to reduce the staining and the poor taste associated with using it.
The Verdict – Which one is better?
Both of them work well but we will have to say that stannous fluoride works better than sodium fluoride since it has additional effects. Both can fight cavities but the former can also reduce sensitivity, kill bacteria, and also improve gum health.
However what you should keep in mind is that toothpastes with stannous fluoride tend to cost more than sodium fluoride based ones. They cost more and they come in a smaller tube so there is a definite price premium there.
- The colgate cavity protection (NaF) is $10 on amazon for a six pack of 6 oz tubes.
- The colgate total (SnF2) is $18 on amazon for a 4 pack of 4.8 oz tubes.
Nonetheless, in our opinion both are still great choices and they’ll always be better than a non-fluoridated or non-remineralizing toothpaste!