The primary purpose of hydrated silica as a toothpaste ingredient is as a whitening abrasive that is used to remove stains, food, and plaque. It is relatively safe to use but it can also be potentially too abrasive when used indiscriminately.
Below is a concise summary of things to know about hydrated silica when formulated into toothpaste.
Hydrated Silica in toothpaste overview:
Description: Hydrated form of silicon dioxide; odorless powder.
Benefits: Whitening abrasive; Cleaning agent; Inert.
Synergists: Aluminum oxide
Side effects: No oral toxicity.
Safety: FDA approved. High concentrations or pyrophosphates increase abrasiveness.
What is Hydrated Silica?
Hydrated silica is the hydrated form of silicon dioxide (SiO2) and it comes in the form of an odorless powder. It can be naturally found in nature from opal gemstones or in the cell walls of diatoms (algae).
Important points to note:
Silica becomes hydrated silica when water is added to it.
A variable number of water can be bonded to silica.
Hydrated silica becomes silica gel when water is removed from it.
The point that I'm trying to make is that this mineral transforms into different states depending on the presence of water. Its name may change but you should be aware that it's still made of the same material.
Common uses
This mineral has a surprising number of uses:
Desiccant.
Paint and varnishes.
Stabilizer in beer production.
Toothpaste whitening abrasive.
Everyone has come across it before but they probably never realized it. You'll commonly find it as a desiccant packaged along with food. Once you realize this, it's an "Ah ha" moment.
These desiccant packets are often in the form of silica gel, which is the dehydrated form of hydrated silica.
Although the rehydrated form is more commonly found in as you guessed it, toothpastes! The reason it is usually hydrated is because toothpaste contains water so it is impossible for it to not be hydrated.
Benefits of hydrated silica in toothpaste
The main benefit of having hydrated silica in toothpaste is in its efficacy as a whitening and cleaning agent.
However, another important advantage with using it is due of its high compatibility with a wide range of other toothpaste ingredients. That means it does not interfere with or react adversely with them.
SiO2 benefits in dentifrices:
Whitens teeth by removing stains.
Cleansing agent by removing plaque.
Thickens the paste.
Compatibility with other ingredients.
May help reduce teeth sensitivity.
Whitening abrasive
All non-peroxide based whitening toothpastes utilize a type of whitening abrasive to remove extrinsic tooth stains and SiO2 happens to be a very popular choice.
These toothpastes may not chemically bleach your teeth since they lack hydrogen peroxide but it can still mechanically remove stains due to the abrasive.
What it is - This type of whitening is akin to scrubbing a dinner plate with food stuck on it.
What it is not - It will not chemically bleach off the stain such as bleaching a wine stained white t-shirt.
Ultimately, whitening toothpastes are typically labeled as such because it contains a type of whitening abrasive.
Helps clean teeth
The abrasiveness of hydrated silica is what helps your toothpaste clean your teeth. It will remove stains, food, and plaque from your teeth more effectively with it in it than without it.
Studies have shown that it is the most effective mono abrasive cleaning agent.
Abrasives it is more effective than:
Calcium carbonate
Sodium bicarbonate
Aluminum oxide
Dical
In summary, you can also think of it as a cleaning agent in the paste. It is similar to how coarser sand paper is more effective at sanding. It is more abrasive than calcium carbonate.
Compatible with other ingredients
A major benefit of using hydrated silica as a toothpaste abrasive is that it is relatively inert which makes it compatible with other ingredients. In other words, it does not react adversely with the other toothpaste ingredients.
Note: Baking soda (sodium bicarbonate) is also very compatible.
Examples of toothpaste ingredients that are incompatible:
Calcium carbonate + Fluoride. They will react together to form calcium fluoride (CaF) which reduces bioavailability of fluoride. That means less of it gets adsorbed into your teeth.
Sodium lauryl sulfate + Fluoride. This will also interfere with fluoride deposition onto enamel, thus reducing its bioavailability.
In summary, certain ingredients react with one another and can produce negative undesirable effects. These effects may reduce the benefits of the toothpaste.
May help reduce sensitivity
It may help reduce teeth sensitivity but the research results seem mixed.
Its abrasiveness could promote greater opening of dentinal tubules which can lead to greater sensitivity.
It could also occlude the dentinal tubules which can lead to a reduction in sensitivity.
Due to the ambiguity of its effects, it is not listed as an anti-sensitivity ingredient. I'm also not sure if I would definitely call it a desensitizing agent either.
Synergists
Studies have shown that hydrated silica was the most effective mono abrasive when measured for its cleaning efficacy. However, when it is combined with 1% aluminum oxide, it was more effective and safer. Therefore aluminum oxide is considered a synergist when combined with it.
Aside from the more effective cleaning, I think the most important synergistic quality would be that it did NOT increase the abrasivity. Essentially this combination manages to increase efficacy while improving safety. That is a big win in my book and I would definitely include aluminum oxide with it in my own personal toothpaste formulation.
Side effects
According to the cosmetic ingredient review, silica in general is safe to use in all types of cosmetic products as long as it is properly formulated.
No signs of oral toxicity were noticed in laboratory tests with mice. It is also non-genotoxic and also non-carcinogenic. Overall, I would consider it as a fairly safe toothpaste ingredient due to the lack of adverse effects.
Is hydrated silica safe in toothpaste?
Hydrated silica is considered safe in food for human consumption by the FDA (21CFR172.480) and that implies it is also safe for use in toothpaste.
Although we're not supposed to swallow toothpaste anyway so it's a non-concern. But it's still reassuring to know that if you swallow a little bit of it, it won't be dangerous.
However, it can be harmful to your enamel even if ingesting it in small quantities is not. This mineral can be very abrasive to the enamel when used in large quantities or when mixed with pyrophosphates.
Large quantities is harmful
Yes, hydrated silica is safe to use in toothpaste but if you put too much of it, it can become too abrasive. If that happens, it can potentially abrade your enamel while you're brushing with it.
Studies have clearly demonstrated that there is a direct correlation between the concentration of silica and its abrasivity.
Toothpastes with 2.5%, 5.0%, 7.5%, and 10.0% were tested.
The most abrasive was the 10% while the 2.5% was the least abrasive.
The reason why it can damage your enamel is because silica is harder than your enamel. When compared on the Mohs scale of hardness, the harder substance can scratch the softer substance.
Mineral | Mohs Hardness Scale |
|---|---|
Hydroxyapatite (enamel) | 5 |
Silica | 6-7 |
What I took away from this was to be mindful of how much SiO2 I would add to toothpaste. It can be harmful if there is too much of it in there so everything in moderation please.
Pyrophosphates make it more abrasive
When pyrophosphates are present together with hydrated silica in toothpaste, it can increase the abrasiveness and enamel wear. In other words, they become synergistic in a sense but in a really bad way with undesired outcomes. The result is greater enamel wear and enhanced erosive enamel wear.
Yes, studies have shown that silica toothpaste is less abrasive and safer on the enamel without pyrophosphates. It also
What are pyrophosphates: These are anti-tartar and anti-staining agents commonly used in toothpastes. They're typically found in whitening or gingivitis control dentifrices.
How to tell if your toothpaste is too abrasive
The most accurate way to know how abrasive your toothpaste is, is by looking it its RDA values (relative dentin abrasivity).
A less precise way of doing it is by feeling how soft the toothpaste feels.
If it melts into your teeth while brushing such as the pronamel toothpastes, then it's probably low abrasiveness.
If it feels sandy or gritty, it may be highly abrasive.
Last but not least, if you are extremely concerned about silica's abrasiveness, you could always opt for a toothpaste with a less abrasive whitener such as calcium carbonate.
Verdict
In my opinion, hydrated silica is a great ingredient to be used in toothpaste since it is a very effective whitening abrasive that will clean your teeth. Then there is also the fact that it is very compatible with other ingredients.
Personally, I would include it as an ingredient in my own toothpaste but I would combine it with aluminum oxide to maximize its effects. Nonetheless it is still good to be conscious of how much of it you put into your toothpaste because it can be harmful if the concentration is too high.
Article written by our dentists in Long Island City.
